Interiorscape Q&A

by Joelle Steele

This is my old horticultural advice column for interior landscape industry professionals. This column is no longer active as of March 2021, but it is a very, very long column, so you can browse it to possibly find answers to your questions.

Q. What is generally regarded as being the ceiling height above which fluorescent lamps are ineffective for lighting indoor houseplants?
A. There is no specific ceiling height at which any lighting automatically becomes ineffective. What you need to know is exactly how many footcandles of light a particular plant requires for maximum health and how many footcandles of light it is actually receiving and for how long each day. You will need to use a light meter. If it is too low (about 50-100fc for low light plants or around 125-250fc for high light plants), then you need to add more light, relocate the plant to a brighter location, or have the light on longer each day.

Q. I cannot seem to get the hang of watering properly. I am always overwatering or underwatering. Is there some trick to this that I am missing?
A. All I can say is that it is not hard once you learn all the basics, and that is too much to give you in this brief format. I recommend that you purchase my book, English & Spanish: Guide to Interior Landscape Maintenance (Inglés y Español: La Guía al Mantenimiento del Paisaje Interior), which covers this subject in detail.

Q. We are maintaining some Bambusa vulgaris in a hotel’s old atrium planter. They are always getting brown tips and leaf spots. I thought it might be due to the coolness of the air in the atrium. What do you think?
A. I think you are partly right. They do prefer to be warm with good ventilation, but it also sounds like you may have a problem with very hard or fluoridated water. I would have the water tested to find out exactly what you are dealing with.

Q. We maintain twenty 15′ Ficus nitida trees in a mall. Eight of them have something wrong with them and I have never seen this before. The bark seems to be peeling off and in some branches there are clumps of leaves which are turning kind of gray.
A. A few years ago, someone pointed out this disease to me and said it was Phomopsis, a slow growing fungus which often attacks ficus trees. This disease is very easily spread from one tree to another by using contaminated clippers, scissors, and other pruning equipment. If left unchecked, it will spread throughout the entire tree.

Q. I take care of four 7′ tall Ming Aralias immediately inside the entry of a highrise building. They’ve been in that location for almost a year. They receive indirect light and they have ongoing leaf loss. If it continues at this rate, they will eventually be bare. I can’t figure out the cause. Could this be a location problem?
A. Probably. Mings are very sensitive plants, and in their present location they may be getting stressed from drafts, dry air, and fluctuations in air temperature. They normally like to be warm and moderately moist. Perhaps replacing them with dracaenas might be a solution.

Q. One of my clients has a very large Asparagus sprengerii in a 12″ pot sitting in a corner window that gets indirect light. It dries out every week because it is so rootbound, but the client loves the plant and doesn’t want me to pot it up a size because he likes the container it is in. Can I trim the roots?
A. You can trim the roots but you can probably just divide the plant, which might be a better alternative if it is very full. Your client will then have two favorite plants.

Q. I find that the lower leaves turn brown and dry out on every Phoenix roebelinii at my biggest account, a mall. My supervisor says I am overwatering, but I say I’m doing just the opposite. What do you think?
A. I think you are right. You may be underwatering. Overwatering usually affects the new growth, and long after the problem is in an advanced stage. Malls are pretty dry and P. roebelinii needs a humid environment. More frequent watering in smaller amounts might help. And, of course, subirrigation containers/devices would be the best solution.

Q. Can I cut back a Dracaena warneckii and root the cuttings? What is the best way to do this?
A. Yes, you can cut it back, and if it is in good light and otherwise in good health, it should sprout some new crowns. However, I recommend that you do this using the air layering method of propagation. This column is too short to explain it, but read a book or check around on the Internet for full instructions.

Q. If my cat eats one of my plants, will he die? I have dieffenbachias and codiaeums.
A. It is unlikely that your cat will eat these plants at all since they don’t taste good and will burn his tongue and mouth tissues if he bites into them. My cats have never shown any interest in my “poisonous” plants — but they have feasted on my marantas and calatheas. I’m always more concerned about a cat digging in the soil of a plant, since it may contain harmful chemicals that a cat can then ingest when he’s bathing himself. Same thing with toddlers eating dirt from a house plant.

Q. Is it necessary to double-pot (with peat) the plants that I then submerge into the soil of large indoor planters?
A. It is not necessary, but it may be desirable, particularly if the plants are rootbound. But if that is the case, you should probably just transplant them first instead. In general, double-potting is more effective with freestanding decorative containers, if the method is to be used at all.

Q. If I put a low light plant in a dark office, will it continue to live but not produce new growth, or will it eventually just give up and die?
A. It depends on the type of plant, how dimly lit that office is, if the plant is pest-free and disease-free, if it was a hardy and healthy plant when first installed in the dark office, etc. But, in general, it will eventually die. How long you can keep it going is quite another story.

Q. I maintain two Phoenix roebellinii palms at a mall. They have good light and lots of new growth. I have recently sprayed both plants for mites, and I would like to know if the spray is what is preventing the new fronds from opening.
A. The spray isn’t the cause, but the mites probably are. They are a cause of stress to any plant, and a stressed plant needs all its resources to fight the mites or whatever else is preying on it.

Q. Should you water an indoor plant with cold water or warm water?
A. Neither. The water should always be room temperature.

Q. I am maintaining indoor plants for a client who travels a lot. All the plants are growing in water only, no soil. The client says I need to check and adjust the pH regularly. Why?
A. For the same reason that you should know the pH of the water you use on plants grown in soil. Most foliage plants like water that is a little on the acid side for optimum growth, and most water sources tend to be more on the alkaline side. If the water in your client’s plants is not the correct pH, the plants may be unable to use their nutrients and may become unhealthy or die.

Q. Some of my residential clients are now bringing their outdoor potted plants inside. What should I do to keep outdoor pests from the indoor plants?
A. Try to keep the outdoor plants in their own room, far away from the indoor plants. Remove any visible pests, debris, etc., from the outdoor plants. Give them one thorough watering to drive out any pests that may still be inside the pots. Be sure to thoroughly clean your tools off after working on the outdoor plants.

Q. Why do rhapis palms always get tips on them?
A. Palms tip when the roots burn as a result of overfertilization, lack of humidity, being rootbound, and erratic watering. Transplant rhapis palms up a size before you install them to ensure they are in soil that will retain moisture and drain well. Don’t fertilize for a year or so, and after that only with a highly diluted fertilizer twice a year during growing season.

Q. I grew a coleus in water that looked gorgeous for ten years. I cut it back periodically to keep it full, got it a bigger jar. I moved and gave it to a friend. Two years ago I rooted some cuttings and they don’t do a thing. Hardly any new growth, poor color. What am I doing wrong?
A. Try relocating the plant to a much brighter location and see if that helps. Also be sure you keep the water clean and that it is room temperature. You might also try adding a very miniscule amount of liquid fertilizer to the water once a month.

Q. I maintain two 10′ Ficus lyrata in an office. The leaves are extremely dusty with no shine at all. A feather duster doesn’t work and I’m afraid I’ll crack the leaves if I wipe them with a rag.
A. If you’re very gentle you should be able to wipe them without damage. You might also be able to lay down a drop cloth and spray them with a leaf cleaner, working from the top down. You’ll still have to do some wiping, but it might minimize your contact with the leaves a little.

Q. I have all the plants in my den in terra cotta containers. The plants are fine but the pots are getting a white crusty film on them. What is causing this and how can I stop it?
A. That’s caused by a combination of hard water and soluble salts that accumulate in the soil and then leach through the clay. You can scrub it off the outside of the pots periodically, but it won’t all come off, and it is pretty much impossible to prevent. Some people think it gives a nice rustic look to the pots, so maybe you could try to appreciate it for its decorative look!

Q. I have a Nandina (“heavenly bamboo”) growing indoors. It is about 5′ tall and very bushy and I’ve had it in the same place and the same pot for ten years. Lately the leaves are turning brown and falling off. Can you tell me what is wrong?
A. If it’s been in the same pot for ten years it could be that you need to transplant it up a size with new soil. If it is rootbound and lacking enough soil to retain moisture, older leaves would die and drop. Or, if it isn’t rootbound, an overly warm room could also cause the soil to dry out and leaves to fall.

Q. I maintain two beds under an inside stairway. The owners want marantas and aglaonemas, but it is too cold and dark for them. The owners know this and always pay for replacements, but it takes so long because I have to pull all the lava rock away and then dig up the plants and replant them and cover them with the lava rock. Any suggestions?
A. If these plants don’t last a long time, why bother to plant them at all? I would just leave them in their pots, submerge them in the soil, cover them with lava rock, and then just remove them and insert new ones as needed. It’s at least a little easier, and in time the pots will lift out more easily, leaving pot-size places in the soil.

Q. Will a Phalaenopsis orchid tolerate being in a sunroom with tinted windows, getting some direct sunlight? I have a new plant and two buds have just fallen off, and one new flower is going limp. I am watering it weekly when the water meter indicates it is dry.
A. I have successfully grown phalaenopsis orchids in full sun without tinted windows. But if the buds are falling off, the plant is probably either too cold or too wet or both. Do not use a water meter as they do not work in bark. The bark should always be slightly damp, but never wet. The plant should also never sit in a saucer that has water in it. You can lightly spritz a little water on the bark surface a couple times a week and that should be sufficient moisture.

Q. Is it okay to put small rocks or glass beads on top of the soil as “topdressing” for indoor plants? I have a client who wants both, and I’m concerned about the weight, and about moss growing or water sitting on top and the soil not drying out between waterings.
A. I use small rocks and gravel in all my plants to keep my cats from digging in them, and I’ve never had any problem. Most of my plants are in subirrigation, so no problem with the soil staying wet in those because it’s always dry on top, but my plants that are in regular pots are fine too.

Q. I have tried to get rid of fungus gnats without using chemicals, including removing the top couple inches of soil and replacing them with clean soil. I also tried a predator. No luck either way. What else is there?
A. Have you tried diatomaceous earth? I have not tried it personally, but I have been recently told that when mixed in with the top 2″ or so of soil, it destroys the larvae. One thing you need to do is to make sure those top inches of soil dry out between waterings.

Q. About six months ago I relocated a Euphorbia trigona for a client. It went from a sunny atrium to a small office that gets sun for about half the day. I had to cut it way back because it was so big, and I haven’t seen any sign of new leaves. Should I be worried?
A. Probably not. Wait until spring and see what happens then. I have drastically cut these back before and they have always grown back.

Q. We installed some Craigii compactas at a bank three months ago. They immediately began losing their lower leaves, which dried out entirely without tipping and fell off. No sign of any pests, not even in the soil. They are almost completely bare now, some having only a leaf or two on each stalk. I cannot tell what is wrong. Do you know?
A. I can’t really tell you what is wrong without seeing the plants, but such a sudden loss of leaves on Dracaenas is often related to abrupt changes in temperature or too much water, possibly soil that is not draining adequately. Perhaps a combination of these things. Since it is winter, my first question would be, does the bank turn off the heat at night or lower the thermostat drastically? And how wet is the soil and are the plants getting adequate light?

Q. No matter how often I spray plants for insects, the pests always come back. Are they just immune to the spray or is there something else I should know before I spray again?
A. The pests could be immune if you’re not alternating sprays often enough. You could also be spreading insects around as you maintain plants, by not cleaning your tools or switching rags between infested plants or between maintenance accounts. You might also not be spraying properly: you need to spray the tops and undersides of the leaves, the nodes, the stems, the soil surface, the saucer/liner, the pot — everything — for full coverage.

Q. When my moth orchid (Phalaenopsis) quit flowering, I cut the stems back and now there are leaves sprouting from them. What does this mean?
A. It means that your orchid is in a good growing location, and it is putting out new plants from the stem, a common way of propagating this type of orchid. Once there are some 2″-3″ long roots growing from under the leaves, you can cut the little plants off and plant them in bark. They should be ready to bloom in a few years if kept in the same environment.

Q. I am the client of an interiorscape company. We have aralias that produce a sticky substance that drips on everything. I have asked that they fix the problem or replace the plants. Nothing is being done. What is the normal procedure for dealing with this type of plant problem?
A. Your plants have either scale or mealybug, plant pests that produce a sticky substance called honeydew. By the time there’s enough of it to drip, you’ve got an infestation that is probably impossible to control indoors. The plants should be replaced, and your contractor should know that and act on it immediately.

Q. I have just taken over maintenance of an office that has about 200 Sansevierias in subirrigation planters between the cubicles. The plants are extremely dusty and all are tipped. I’d like to hose them off, but I don’t want to damage the subirrigation systems. What should I do?
A. Since all subirrigation devices work a little differently, you should contact the manufacturer and find out their recommendations for cleaning the plants. Also, you might want to find out how to adjust the devices so that you can get the watering right and eliminate the tipping, provided that problem is not a result of overfertilization or an excess build-up of soluble salts in the soil.

Q. I installed Marantas as a ground cover in an atrium, and they are receiving adequate light, air circulation, and water — soil is evenly moist, room not too warm, moderate humidity — but they are tipping very badly and the client is complaining. Was this a bad choice for an atrium? I thought they would do well and they looked great when first installed.
A. This sounds like a hard water or overfertilization issue. I would check those two things first. Marantas do not like hard water and they don’t require an abundance of fertilizer. Tipping is a sign of both.

Q. We are maintaining a large atrium that is planted entirely with cacti and succulents in a “rock garden” setting. An 8′ cactus has three soft spots on it, and it was that way when we took over the account. Does this mean it is rotting inside? Should I just leave it alone and let it recover, or should I replace it?
A. If the soft spots are on the surface only, they may just dry out and leave a scar. If they are coming from inside the plant, then it could very well be rotting inside, but not necessarily all over the plant, maybe just in that area — trunk or arm. It all depends on where the soft spot is and how deep it is. This is a “keep it dry” and “wait and see” situation right now.

Q. Is there anything I can do to get rid of scale on my indoor Ficus tree? I have taken it out and hosed it down several times and the scale doesn’t come off.
A. You can’t just hose off scale. You need to spray the trees with a pesticide designed specifically for scale. Bring the tree outdoors and spray it thoroughly in the shade or on a very overcast but not cold day. Be sure to spray under the leaves and on all the little stems of the tree, spray the trunk, spray the pot, and spray the soil surface too. Check to see that the tree is not under stress due to lack of water — perhaps it’s rootbound/potbound and needs to be potted up a size with fresh soil, or maybe it has adequate soil but is in too warm a spot and is drying out between waterings as a result. Water stress just makes any pest problem worse as it weakens the tree.

Q. Can you tell me how to control Phomopsis in a Ficus benjamina?
A. Phomopsis is a fungus that is easily passed from plant to plant by using unclean tools, rags, feather dusters, etc. It is also caused by water stress. So, keep your tools clean, learn how to water correctly, make sure the plants are in sterile potting mix, transplant them up a size and into a sterile potting mix if they are rootbound/potbound. Depending on where the trees are and what the laws are in your area, you may also be able to treat the plants with a fungicide, but this will not stop the cause of the problem. Contact your local agriculture department regarding the use of a thiophanate methyl fungicide for control.

Q. All our techs have moisture meters, but they still seem to mess up on the watering. I know the moisture meters stop working after awhile, but we replace them early on to be sure they are all working. Any idea what we might be doing wrong?
A. If the meters are working but plants are being consistently under- or overwatered, it could be that the plants themselves are causing the misreadings. A plant that needs to be transplanted will not likely have much soil and you may get a false reading. Or maybe the techs aren’t probing the meter into the soil in different places to verify the reading. Part of the plant could be dry and another part very wet — side to side or top to bottom, with the bottom of a deep container very moist and the top being dry. Most of these problems can be eliminated by transplanting or soil changing, in addition to more fastidious checking with the meter.

Q. Is it possible to grow Fuchsias and roses inside the house, or can they only be used there for a short time as seasonal color?
A. I have tried to grow a lot of outdoor plants inside, including fuchsias and roses, and to date the only thing I have had success with is “heavenly bamboo” (Nandina domestica). If any readers have had success with outdoor plants growing indoors, please drop me a line.

Q. Why can’t I get orchids to re-bloom? I buy beautiful moth orchids (Phalaenopsis) for my clients but they always rot or just fail to flower again.
A. In addition to light, orchids need a humid environment with good air circulation. Light is not usually a problem, but it is hard to get adequate humidity and air circulation, especially in office buildings. However, in a residence, you might have better luck if you are in a moist climate and the client is willing to crack a window open. Other than that, you might want to bring the plants back to your greenhouse, if you have one, and allow them to flower there. As for rotting, don’t soak them; they do not need an abundance of water, just moisture from the air.

Q. All of the bark chips at one account are getting white with mildew. What causes this?
A. Dampness. The air may be damp and/or the soil is staying too wet between waterings, thereby keeping the bark damp too and causing it to mildew.

Q. What do you think is the best material to use to raise a grower container up inside a decorative container?
A. I personally like newspaper, because if you roll and shape it properly, it won’t move when the container is moved. The other option is “styrofoam” pellets or peanuts, although I recommend the organic ones rather than the synthetic, as they are biodegradable. But the pellets don’t always hold up as well as the newspaper, and they can be messy to deal with if you use the synthetic variety.

Q. I am relocating cross-country and want to bring some of my small plants with me, including a few orchids. Should I take them on the plane or ship them by truck?
A. I recommend that you check them on the plane. I have done this with pottery and other fragile items and if you pack them really well, they will survive the baggage handlers. Make sure they are only damp and not wet or dripping. Pack newspapers or bubble wrap all around the bases of them to keep them from tipping over. Mark the box “THIS END UP” in very big red letters with an arrow facing up. Mark this all over the box. Since it is a short flight, you shouldn’t have to worry about making any air holes. Be sure that your name and phone number and address are highly visible in a couple of places on the box.

Q. We maintain an atrium in which the Ficus trees were planted in their grower pots and then submerged in the soil. They have grown too tall and we would like to trim them but don’t know how much foliage to remove. Also, we would like to transplant them, but don’t know if we should trim the roots first and put them back in the grower pots, which I believe was done to slow their growth.
A. If you trim the roots before you trim the foliage, you will have a lot of bulk to maneuver around in the transplant process. (And no, I would not put them back in the grower pots.) But, if you trim the foliage first, and the trees are extremely rootbound, you might not get your foliage back in full for a good long time. Since spring is almost here, I would trim the foliage first and hope it comes back and that the roots will make it another year, and then trim them in the spring of next year.

Q. A Dracaena massangeana I maintain has been turning very yellow from the tips inward on the older leaves. It is not in a window and it is planted in lava rock. What might be wrong with it?
A. Probably underwatering. Plants in lava rock can’t retain moisture out on the job. Add a warm environment such as you get when the heat is turned on during the winter, and the plant simply dries out, while at other times of the year the water just sits in the saucer and rots the roots of the plant. Remove most of the lava rock from the roots and transplant it into a good indoor potting mix.

Q. I have problems with fungus gnats in the soil stored in my greenhouse and on some of my interior landscape job sites. How can I get rid of them?
A. If your soil or potting mix is contaminated, you need to get rid of it — possibly, probably all of it. Clean the areas where it has been stored, spraying with insecticide if necessary. Wait about two weeks and then purchase all fresh, uncontaminated soil/mix. To avoid future contamination, do not store your soils and potting mixes on or near soil surfaces or around plants, and be sure to keep tools and supplies clean after each use.

Q. We are going to replace a 10′ x 20′ bed of 16 10″ Chinese evergreens because they are very old and scraggly. They are also very difficult to keep clean. The area is extremely dusty and there is no drainage, so we can’t hose off the plants every few months (hand-cleaning takes too long and access is difficult). Do you have any suggestions for what we might do?
A. I would begin by removing all the soil from the bed and replacing it with gravel. Then, I would either put the new plants into deco containers or planter boxes and place the decos or boxes on top of the gravel. If it is not possible to place the plants that high and they need to be below the soil line, then I would implant a larger grower pot into the gravel and place the plant’s smaller grower pot into it for easy removal. When you need to do a major cleaning with a hose, simply remove the plants to an area where you can do so, then put them back in place when the excess water has drained off.

Q. I installed two large Spathiphyllums. Within just a few short weeks the client called and said the plants were dying. They were completely drooped over onto the floor. I found some millipedes in the soil, but they had not damaged the roots. I cut back the stalks and watered the plant, which I now sense is a water hog. I don’t want this to happen again. What do you suggest?
A. In the future, you should make sure you don’t install a spath that is rootbound, make sure the level of service is frequent enough to keep the spaths well-watered, and consider placing them in subirrigation devices to prevent wilting.

Q. A Euphorbia trigona in a stairwell next to a window has been turning brown on the trunks. It is still producing new leaves. But the browning makes it very unattractive. I can’t see any signs of disease. Could it be burning?
A. Absolutely. They can take a lot of light, but they often burn when hit by direct sunlight, especially when it comes through a window. You can move it to stop the burning but the browning that is there will not go away.

Q. I am an in-house maintenance technician. I take care of a 6,000 sq ft atrium. There are 20 Caryotas, all over 15′ in height and half of them are suffering from dry, dead, dark reddish edges on their older leaves. They do not have mites and they are on a drip system.
A. Sounds like a combination of overfertilization and underwatering. Even if your Caryotas are in the best of light, you can still overfertilize them if the drip system does not flush the nutrients from the soil. Drip systems often need periodic adjustments to make sure that they are watering sufficiently. You may need different emitters that dispense water at a greater rate, or you may need to adjust the timers on the system for longer or more frequent applications of water.

Q. My 9′ Ficus tree has lost almost 75% of its leaves. A friend told me I should trim the roots and cut back all the branches, but I’m afraid I’ll put it in shock and the leaves will never grow back. What should I do?
A. If this were spring, I would tell you to cut it back to just a few branches after you transplant it. The leaves do grow back and Ficus trees are very hardy. But since it is not spring, I would trim back the branches a little and transplant it into a larger container using all new indoor potting mix. Shock occurs when the roots are traumatized, but the biggest cause when transplanting is lack of moisture. Make sure the soil is thoroughly moist from top to bottom after you transplant. Then check it a week later to see how the plant is doing. Don’t let water stand in the saucer. Make sure your Ficus gets good light but not so harsh that is burns the leaves or turns them yellow. Also, before you do anything, check very carefully to be sure you don’t have pests that are causing the leaf loss.

Q. Is it better to look at the footcandle hours for a plant or just footcandles?
A. Footcandle hours refers to the amount of light a plant receives in any given day. It is not necessarily superior to looking at just footcandles, but it is a way of looking at the total light exposure the plant receives over the course of a day. You still want the footcandles to be in the right range for the plant(s) in question. But you might want to know how much total light the plant is receiving of those footcandles. For example, if you have a plant in an area where there is natural light only in the morning and then that part of the building is in shade with only artificial light in the afternoon, you might have two different footcandle measurements, and so you might be multiplying the natural light of 2000fc times 4 hours and the afternoon light of 800fc times 5 hours for a total of 12000 footcandle hours.

Q. I have two 7′ Ficus benjaminas. There is a mostly clear, sticky substance on top of the leaves. Some of it is a little whiter and thicker. You can’t see it dripping but it is getting onto the floor.
A. It sounds like scale or mealybug. Since you don’t see anything but the sticky substance, my guess is that you have scale, which is much less obvious to an untrained eye. It looks like little black or soft brown shells on the plant surfaces. Scale produces a clear, sticky substance called honeydew. It is important that you control these insects immediately, and I suggest that you hire a professional interior landscaper to spray them with an appropriate pesticide, as this much honeydew signals a substantial infestation.

Q. Six months ago, I got a large Ficus tree that I cut back and repotted. It had a black mold on the leaves. I have misted it and cut the moldy leaves away but it seems like a losing battle. Is there anything else I can do to treat it?
A. Your Ficus has black sooty mold. Don’t mist it because mold thrives in humidity. On a warm, dry day, in the shade, hose off the tree to clean the leaves. Let the leaves dry thoroughly, helping that process along by wiping them off with a clean, soft cloth. You might want to use a leaf cleaning product rather than water alone, to clean off the leaves.

Q. One of my clients brings chrysanthemums to the office and places them around the base of a Dracaena massangeana. The mums often have mites and now the Massangeana does too. The tree looks bad and she wants me to replace it at no charge. I can’t afford to replace it and maintenance is an ongoing battle with the mites.
A. This problem only emphasizes the problems of not having a proper maintenance agreement. You need one that states that you do not replace plants that are exposed to infested plants that the client brings in. That will enable you to handle these kinds of problems should they occur.

Q. We rent plants for parties, mostly Ficus trees and Scheffleras, from our stock of about 80 plants. We store them all under a shade cloth and we can’t seem to keep them healthy and alive. What could we be doing wrong?
A. Regularly moving plants in out and out of different environments is very stressful for plants, and there could be many other reasons for fatalities as well. In general, plant rental companies have large greenhouses full of plants and don’t rely on the same ones for rentals, so the stress is minimized and the care is by professionals. You need a much larger inventory or be prepared to replace plants as they die. Have you considered the very realistic high-end silks and artificials as an alternative to live plants?

Q. One of my residential clients has a Ficus benjamina that is about 30 years old. It is healthy but it is badly misshapen. She is willing to let me prune it back substantially, but I don’t want to go overboard and end up killing it. What do you suggest?
A. It is hard to kill these trees by over-trimming. You can cut them back all the way to the trunk in March and they will have new growth in April, provided they have adequate light. I have re-shaped Ficus trees in this way and have never lost one. You do have to wait awhile until they are fully grown in, but they do come back looking much improved in the long run.

Q. Two years ago, and against my own better judgment, I installed bamboo (hat my client had purchased on her own) directly into large, expensive, decorative containers that she supplied. The bamboo is in a solarium and it is a mess. I have an ongoing mite infestation that I can’t ever seem to control, and two of the bamboos have grown so much that they are already rootbound. I’m afraid they will soon crack the deco containers. The problem — besides the obvious — is that the client actually thinks the bamboo looks great. I say it’s just a matter of time before it’s all dead and the pots are in pieces. What do you recommend?
A. A formal letter to the client stating exactly what is happening, the probable outcome, and suggestions for solutions: 1) removing the bamboo from the pots, spraying it thoroughly for mites, dividing the plants, planting them into grower pots, and placing the grower pots into the deco containers; 2) removing the bamboo immediately, cleaning out all the containers and the surrounding areas, and replacing the bamboo with a more suitable plant that has the feathery, upright look of bamboo but that is more resistant to pests.

Q. Is it possible and/or wise to dig up and divide an eight- year-old Rhapis. It’s planted in an outside raised bed (in Florida). The plant is about 8′ tall and 4′ wide and was planted 7-8 years ago. My client wants to dig it up, divide it, and plant a 2′ section in a grow pot and then place it inside. The spot has good strong light. Your advice?
A. I think it is possible to do this, but I would do it in either early fall or early spring, whenever you have rain or when the growing season starts (when days lengthen). If the plant outdoors is in a shaded or indirectly lit area, I would make sure the part of the plant that goes indoors is in a similarly lit area, not in a hot window. If you can just remove the 2′ section without digging up the entire plant that would be best. But do be very careful with the roots when you dig and be sure to keep both plants well watered, but not wet, for the first few weeks or so until they re-establish themselves.

Q. We have an ongoing battle regarding the use of feather dusters. We know they can spread insects, but some of my best people believe that if used intelligently they are a great tool to keep most plants clean. I know in one of your books you say absolutely no dusters. How do you feel now and can you expand on your thoughts?
A. I don’t like feather dusters because they do spread insects, and since you can’t always see the pests in their earliest stages, this seems like a substantial risk to me. Also, most dusters don’t really remove dust all that well; they simply launch it into the air where it settles onto the surrounding areas and ultimately back onto the plant.

Q. I am placing two 10′ palms in the doorway of a grand foyer opening onto a living room. I originally wanted to use Kentia palms, but I’m afraid they will get battered over time. Can Rhapis palms tolerate such a drafty location?
A. If it isn’t too cold or too constant a draft they should be fine in that type of location. But I recommend that you consult a nursery or grower in your area to verify this.

Q. How much and how often should I water a Dracaena warneckii? It is 5′ tall and in a 10″ container.
A. No two 5′ tall, 10″ container D. warneckiis are watered the same. It depends on the temperature of the environment, the amount of light the plant is receiving, and the condition of the soil. You need to learn 1) how to spot the slightest wilt in the leaves; 2) how to distinguish between wet/moist soil and cold soil; and 3) how to judge the environmental factors that affect water usage by the plant. A plant’s water requirements also vary throughout the year. There are no easy shortcuts to watering a plant, but once you learn the basic principles of watering you will find you always know how much to water and when.

Q. I took over an account that has a 12′ x 18′ planting bed in a lobby/atrium area with Marantas and Calatheas used as a ground cover. They all have dry edges and brown tips, no spots of any kind. I have already had to replace about a fourth of them. What is wrong?
A. It sounds like hard water or fluoride toxicity, possibly underwatering and lack of humidity. Could be a combination of all of the above. You need to thoroughly assess the situation: test the pH of the water and soil, make sure you are not overfertilizing and/or underwatering, find out exactly what the drainage is in the bed, etc. Once you know exactly what you are dealing with you will be able to achieve a solution.

Q. I have two large planters in a hotel atrium. The two big Dracaenas appear to be suffering from some kind of deficiency, possibly iron. I have been fertilizing but there has been no improvement.
A. You may have a hard water problem. High alkalinity can interfere with a plant’s ability to absorb nutrients. Unless you understand how to properly test the water and soil, I suggest you contact a soils lab and have them test for you to see exactly what you are dealing with before you attempt further solutions.

Q. My cat chews on my houseplants. What can I do to make him stop?
A. I have only found one successful way to deter my cats from chewing on my plants, and that is to make a paste of water and cayenne pepper and smear it on the stems and undersides of the leaves that are at the level the cat can reach. I also recommend that you try to lure the cat away from your plants by giving him a pot filled with his own growing rye grass or catnip. You can buy the seeds in most pet stores or over the Internet.

Q. A client received a gift plant. It has variegated leaves, is about 5′ tall, and is in a 10″ pot. There was a small tag that said it was a New Zealand Birdcatcher Tree. There are no instructions for its care and I’m not even sure if it belongs indoors.
A. Your plant is a Heimerliodendron brunonianum variegatum, also known as a Pisonia. And it does come from New Zealand, and you can grow it indoors. It needs really good but indirect light to maintain the variegation in the leaves, and it needs a fair amount of humidity. The soil needs to be kept evenly moist and the plant should not be allowed to dry out between waterings. I kept one of these for about 12 years in a Natural Spring container until a window was left open and it succumbed to aphids.

Q. Kind of an unusual question, but can you grow a Eucalyptus tree indoors?
A. I have no idea. Perhaps someone reading this will know and I will publish their insights. I love Eucalyptus trees and I think it would be great to have one indoors, like a silver dollar, perhaps.

Q. The Kentia palms in a highrise office building lobby that I maintain have plenty of light, but when new growth appears, the fronds tend to turn very dark, almost black, and they never open. Am I underwatering?
A. No. Sounds more like cold damage. Some buildings have thermostats that are automatically turned way down at night or on weekends to conserve energy. You may wish to discuss this with the building management to see if they can keep the temperature at least 52°F in the lobby where the kentias are.

Q. I want to run my business without using harmful chemicals, but I can’t seem to do it. I always have to use chemical pesticides to eliminate the infestations of mites, mealy, and scale. I can’t afford to just replace plants. What do you suggest?
A. Some preventative maintenance. 1) Buy your plants from a reputable source and check them out thoroughly before you install them. 2) Always clean your tools (clippers, scissors, water meters, etc.) with alcohol and use fresh rags at each account. Try to avoid using dusters as they just spread pests and diseases. And remember that if you wear gloves, you can carry things on them from one account to the next. 3) Make sure the plants you care for do not become stressed, particularly from lack of water or erratic watering, as that can make them more susceptible to complete infestations. 4) If your plants have pests or diseases, isolate them immediately to avoid spreading the problem to other plants nearby. 5) Use insecticidal soap at the first sign of a problem.

Q. I maintain a lobby which consists of two small planter beds next to each other filled with Chinese evergreens (Aglaonema commutatum). The bed on the floor has intermittent problems with leaf damage which the bed above it never has. Some of the older leaves turn mottled and chlorotic. Do you know what causes this?
A. It sounds like it could be cold damage. A floor bed is more likely to be colder at night than the bed above it. You might want to check on what the overnight temperatures are in the lobby because aside from raising the temperature slightly at night, there is no specific cure for cold damage.

Q. I took over the maintenance of a recently installed 5′ Norfolk Island pine (Araucaria heterophylla). It’s in a southwest window of a bank lobby. It looked fine six weeks ago but now it is getting brown tips on the needles and is shedding a little. What am I doing wrong?
A. It is probably the location. Banks tend to have dry air and a southwest window may offer good light but could also be very hot. You can’t do much about the dry air, but you can suggest that the plant be relocated into indirect light. Also, check your watering and consider the fact that these plants do much better indoors in subirrigation.

Q. Our maintenance uniforms have brownish stains on them which I think is sap from Ficus trees. We launder all uniforms in-house and can’t get these stains out. Do you have any suggestions?
A. An interior landscaper once wrote to me and said that she used straight rubbing alcohol rubbed onto a fresh stain to remove it, and that one of her employees used straight bleach on a toothpick. She also told me that she had read about sponging dry-cleaning solvent into the stain and letting it dry, then soaking the stain in a solution of liquid laundry detergent and ammonia, and finally laundering with the liquid laundry detergent. I haven’t had occasion to try these methods, so I don’t know if they work or not.

Q. I would like to use river rock as a top dressing under some large palms I am installing, but I have had problems with molds growing under the rocks in the past. Is there something I can do to prevent this?
A. If you use a subirrigation planter or device, the soil on top should remain dry and in my experience this eliminates the problem. Otherwise, you may have to rely on fungicides.

Q. Every time we water the hanging baskets at a restaurant, they drip. Is there anything we can do to prevent this?
A. Are you talking about moss baskets? If so, they are a poor choice for use indoors, and there is no solution to the problem but to replace them. They leak, period. If the problem is with plant containers placed inside baskets, that is a different story. You can start by making sure that the plants themselves are not rootbound, leaving insufficient soil to retain water. If that is not the problem, then you might want to use a deeper saucer/liner in the base of the basket and, as an extra precaution, you might want to line the basket with plastic. Take them down when you water them next time so that you can observe the cause of the leakage.

Q. Are there any plants which do better in low-light, around chlorinated pools and hot tubs?
A. Consider the humidity and air circulation (or lack of the latter), potential for splashes onto the foliage, and the proximity of the foliage to the water itself when selecting your plants. Think about where they grow in nature. On the whole, fine-leafed, shallow-rooted herbaceous plants such as Pothos, Cissus, Syngoniums, etc., do not usually do well in such environments, particularly the closer they are to the water itself. Ferns do well in most cases, but some varieties such as Bostons can be messy and therefore expensive from a maintenance standpoint. Polypodiums and similar types of ferns would be neater. Woody plants like Ficus should do well as would most epiphytic plants such as staghorn ferns, orchids, and bromeliads.

Q. I maintain a small bed in the lobby of an office building. I put in spaths (Spathiphyllum) but the blooms only lasted a week due to the hot overhead lights which are on all day long. Now I have Aglaonema, palms, and Cissus. They look good, but my client would like some color. Any suggestions for something that can take the heat?
A. Have you tried bromeliads? They are really the only thing I can think of that would tolerate the dryness between visits. The other option is to go with subirrigation so that you can avoid the drying out. With a subirrigation system in place, you could do a regular color rotation using the flowering plants of your choice.

Q. I maintain four large variegated ginger plants (Alpinia) in a shopping mall planter. They looked fine when first installed a year ago, but they are looking worse every day. They have brown edges and tips on the leaves but I am sure I am giving them enough water. Do they need even more?
A. Gingers prefer humidity and the mall is probably just too dry for them. They might need a little more water but check the soil carefully, using a probe if possible, before increasing the water. If all else fails, perhaps you can replace them with more tolerant plants.

Q. There are so many subirrigation systems and I am confused about which one is best. How do I decide?
A. Determining which system works best for a particular type of planting application is the question you really need to answer. I recommend that you purchase one of each system and experiment with all of them to learn exactly how they work. They all vary in cost, planting application, and ease of installation and maintenance. For example, you might end up selecting something as basic as a small wick device for one project, and something as sophisticated as a custom-finish, fully-enclosed, stand-alone reservoir system for another. In between those extremes are several other viable systems. It just depends on the job.

Q. We took over the maintenance of a restaurant with spider plants (Chlorophytum comosum) in a window hanging over planters filled with grape ivies (Cissus rhombifolia) and two Rhapis palms (Rhapis excelsa). The spiders are severely infested with scale but the ivies and palms beneath them seem unaffected. Is this just luck or am I in for some major pest problems down the road?
A. I have never seen scale on Cissus or Rhapis, but that doesn’t mean it can’t happen, and I’d rather be safe than sorry and replace the spiders with pest-free plants, preferably not Chlorophytums.

Q. A few years ago I installed twenty 4″ Schlumbergera and ten 4″ Zygocactus in a narrow planter box in an eastern window. They have been doing well and they bloom beautifully once a year. The problem I am having is that they are getting very droopy and leggy. Can I prune them?
A. Yes, definitely. I prune mine back every year a month or so after they have stopped blooming. They grow back very full and bushy and always bloom again the following winter. I take them down to about an inch or so above their hard brownish stems but you may want to leave them a little longer. They usually start budding new growth in a couple months or so.

Q. We have always had good luck with Rhapis palms. But recently, two in a client’s executive office have displayed brownish blotches on the leaves. None of us can figure out the cause. Any ideas?
A. Two come to mind: burning from a leaf shine or leaf cleaner, or air pollution. If you recently cleaned the leaves, probably using an alcohol-based cleaner, they could burn. Use only water to clean palm leaves. If you haven’t cleaned the leaves, have there been any changes made to the office? Any major cleaning by a janitorial service? Have you or your technicians ever noticed any unusual odors? Is the office in an area with extremely bad smog? You’ll have to play detective a little while longer or take a sample to a plant pathologist.

Q. When I visit one of my residential clients on Monday mornings, her plants have dew on the tips of the leaves — indoors! What causes this?
A. What you are seeing is called guttation. This happens when water from the plant’s system is released to the leaf surface because humidity is so high that the plant is unable to lose the moisture naturally through evaporation.

Q. Some of our Ficus trees are exhibiting very pale, almost white, new leaves. We have tried adding iron (sequestrol) to the soil, but with no improvement. Is there something else we could try?
A. Iron may be what these trees require, but iron may not be available to the plant if the soil is particularly alkaline. I would recommend that you do a pH test on the soil and on your water source. If it registers 7 or above, you can add calcium carbonate to the soil or common household vinegar to the water to make the iron available again.

Q. Which leaf shine products work best? Are there any organic leaf cleaning methods that might be less expensive?
A. If you want a ready-made product, I would opt for a leaf cleaner. They all work, some better on certain kinds of plants than on others, and you should try a few until you find ones you like. If you just want a natural sheen to the leaves, nothing works better than plain old water on a soft rag. Use disposable rags or thoroughly clean your cloth ones in hot soapy water before using them on another plant.

Q. I am having trouble with a Ficus tree. It has brown tips on the old leaves and the new growth is coming in very tiny and pale and then shriveling up to a blackish-brown. The office was painted four months ago and all the other plants were fine but this one has been in this condition ever since.
A. It might be mercury poisoning. Airing the office out could help, but some ficus trees are so sensitive to the mercury in paint that they have to be relocated for several months.

Q. A residential client of mine had the glass in her bay window tinted. I moved some of her plants there because I thought they would be okay with the filtered sun. A few days later, she called to say that everything was wilting and burning. How could this happen?
A. There are different kinds of tinting products and processes. Some may give the illusion of dimmer light when only one band of the spectrum has been reduced. Also, even if there is less light, there may still be enough heat produced to wilt the plants.

Q. We are going crazy with fungus gnats at several of our accounts. One office has them all over the ceiling. How do you get rid of them? I prefer not to use chemical pesticides if possible.
A. The flyers only live about a day or two, so you need to get rid of the larvae living in the soil. To do this without pesticides, remove the top two or three inches of soil and replace it with fresh, uncontaminated potting soil. Be sure to clean the pot and saucer thoroughly. Then, when you water, make sure that you do not water so heavily that it sits in the saucers overnight or that the top of the soil cannot thoroughly dry out between visits.

Q. My technicians seem to go through a lot of moisture meters each year. The devices suddenly stop measuring the moisture accurately. Do they need to be stored a special way to extend their usable life?
A. The sensing portions of moisture meters, (which actually measure soluble salt levels in the soil), become eroded with repeated use. As a rule of thumb you should replace them about every six months, possibly even more frequently if your technicians rely heavily on them.

Q. I find that the lower leaves turn brown and dry out on the Phoenix roebeliniis at my biggest account, a mall. My supervisor says I am overwatering, but I say I’m doing just the opposite. What do you think?
A. You may be underwatering. Overwatering usually affects the new growth long after the problem is in an advanced stage. But, the real problem is probably just the fact that P. roebelinii needs a humid environment and malls are usually pretty dry.

Q. Many of my clients have cancelled or drastically cut back on color rotation. Many of them want me to find something that lasts longer or that is a permanent source of color. It seems that something like Bromeliads or Phalaenopsis should fill the bill, but cost-wise they are about the same.
A. You can probably extend the life of some flowering plants by potting them in subirrigation. If you have clients who demand color but not necessarily in the form of flowers, you can try adding some colorful foliage plants such as Codiaeums, Marantas, or Calatheas.

Q. I recently ordered 10 Kentia palms. We unsleeved them right after they were delivered and found that the new growth was partially black. I called the supplier and he said to just cut off the black parts. I am worried because I am afraid the plants might be diseased.
A. It sounds more like they were cold damaged in which case removing the damaged leaves should end the problem, as long as you are moving them to a warmer location (50 degrees Fahrenheit or higher).

Q. A large corporate client of mine routinely replaces all their fluorescent light tubes. I would like to be sure that they use whatever type of fluorescent light is best for plants. What would that be?
A. Cool white are considered the best because they cause the foliage to expand laterally and the stems to elongate slowly.

Q. Some of my residential clients have African violets and I can never get them to bloom. They have good light, but they always seem to wilt and rot before they ever bloom.
A. It sounds like you may be overwatering them. They should be allowed to almost dry out between waterings. They also bloom better when potbound, so keep them in their little grower pots as long as you can, or group a bunch of them together in a subirrigation planter. And, don’t forget to use a fertilizer specifically for African violets.

Q. I have two Asplenium at one of my residential accounts and they look awful. Some of the leaf edges are very dark, almost black, and some of the tips are yellow with brown spots. Some of the leaves have big brown blotches on them, and some of the leaves just turn brown and shrivel up. What am I doing wrong and how can I fix the problem?
A. In their natural habitat, Asplenium are epiphytic. When potted and living indoors, they can be temperamental if conditions are less than ideal. The dark edges are probably from too much heat or from a pollutant such as an aerosol spray. The yellow tips with brown spots are usually caused by abrupt changes in temperature to which these plants are particularly sensitive. The brown blotches would indicate that the plant was too cold, too wet, or both. Let your client know that the room has to remain warmer so that the plant can dry out between waterings. As for the leaves that turn brown and shrivel up, this is from drying out too much between waterings. It sounds like you have a combination of things going on with these plants, the least of which is erratic watering. You need to give them a little more attention to insure that their special needs are being met.

Q. Last year we cut back all the Pothos at our accounts. This year, the new growth is pale and unvariegated. The plants look sickly. What can we do to get the gold back into the leaves?
A. You need more light. Without good light, the leaves will come in solid green. The fact that your new growth is also pale would seem to indicate that these plants are currently existing in very low light conditions.

Q. I would like to recommend succulents to some of my clients who want ultra-low maintenance costs. Do succulents do okay in office buildings? I am mainly concerned about the extreme temperature changes on weekends.
A. Most succulents will weather the temperature changes pretty well. But, succulents are not necessarily ultra-low maintenance. They are like foliage plants in that they all have different watering needs, they can dry out, they can rot, they can become diseased, they must be fertilized, and they require weekly watering, sometimes twice weekly during warm weather. The only way you can make them lower maintenance would be to plant them in subirrigation.

Q. What is the best way to clean the brittle leaves of plants like the Codiaeum or Ficus lyrata?
A. If you can just rinse them off that would be the ideal solution. But, since that is rarely feasible indoors, you should use a very wet, very soft cloth, and just be as gentle as you can. Avoid applying any oily substances which will attract and hold dust as that would just make it a job that has to be done more frequently.

Q. The Phalaenopsis at one of my residential accounts has root mealy bug and I can’t seem to get rid of it. The client does not like me to use pesticides so I am at a loss for what to do. Are there any non-chemical treatments that I can try?
A. When my orchids got root mealy a few years ago, I removed them from the bark, discarded the bark and then washed the containers and saucers in hot soapy water. I rinsed the roots and the lower portions of the plants in tepid, soapy water and thoroughly rinsed them in clear running tepid water. Then I got new bark and repotted them. They have been fine ever since.

Q. Many of my residential clients have plants which they bring indoors when they are in bloom. I know that this spring they will want me to bring in their geraniums and azaleas, and I really don’t like to do this because there always seem to be pest problems that come with them. What can I do to limit the amount of pests that come indoors?
A. Short of keeping them healthy in the first place or spraying them with insecticide before bringing them inside, I don’t know what else you can do as far as eliminating the pests entirely. But, you can try to keep these flowering plants away from the indoor foliage plants as much as possible. Also, when you are maintaining plants, don’t use your clippers, scissors, rags, etc., on the outdoor bloomers. Use two separate sets of equipment and keep them in separate containers stored away from each other to avoid contamination.

Q. Two years ago, we installed 6″ Hoya carnosas in an indoor, very well-lit, arbor-like setting that is an employee dining room. They have not bloomed yet and the client is complaining. We have fertilized but there are not even any buds.
A. I have several different kinds of Hoyas. One of my 6″ Hoya carnosas just started blooming two years ago. I have had the plant for five years and it gets excellent light. My H. carnosa `Hummel’s compacta’ has yet to bloom after almost seven years. I spoke to a Hoya expert about this a couple years ago and he said that with the exception of the H. bella, most of these plants take a long time to establish themselves and mature sufficiently to flower.

Q. We just took over the maintenance of a hotel which has six Caryota mitis in the lobby. My partner and I have never maintained Caryotas before. The leaves have rust-colored edges and the client has not complained, but we are concerned.
A. These plants can be temperamental, particularly when it comes to temperature and humidity. They like a high degree of both and do not always do their best in air-conditioned rooms such as hotel lobbies. It sounds like they might be suffering from a little underwatering combined with low humidity.

Q. The Chinese evergreens (Aglaonema commutatum maculatum) which we have in a large open planting area in an indirectly-lit lobby are almost four years old. They are growing very tall and leggy. It would be labor-intensive to dig them up and plant new ones because of the way the planter is situated. Can we just cut them back? If so, how far?
A. Yes, you can cut them back. I would recommend cutting back only a few stems here and there and leave plenty of foliage growing around them as they are very slow to grow back. Just use a clean pair of clippers and cut just above a node. You can cut a stem down almost all the way to the soil line if necessary.

Q. I love the airy look of ming aralias (Polyscias), but have always avoided using them because they seem difficult to maintain. Now, I have inherited an account that has two of them. They get little groupings of brownish-yellow leaves and I don’t know what is causing this. They are in good light and I think they are being watered correctly.
A. When I had this problem several years ago it was immediately solved when the trees were planted into subirrigation planters. So, I suspect that it is a water-related problem. You should make sure that the plant is always kept evenly moist but not wet. Subirrigation might be the ideal solution for such delicate plants.

Q. We have problems with chrysanthemums frequently being delivered infested with thrips, whitefly, and/or aphids. Can you recommend a product that we could use to control these pests either on site or in our warehouse before installation?
A. I recommend that you find a reliable supplier rather than continue to patronize and/or accept deliveries from one(s) that delivers infested materials.

Q. We have about 100 large bags of soil in our warehouse and they have some sort of small worm-like bugs in them. We don’t want to use the soil but we can’t return it because it was fine when we bought it a year or so ago. Can we bake it to purify it? If so, how?
A. You can, but it seems like it would cost you more to do that than it would to dispose of the soil and buy new. If you decide to bake it, you need to use either dry heat, hot water, or steam. Bake the soil for about twenty minutes or so at approximately 120 degrees Fahrenheit.

Q. Six months ago, I took over maintenance of an indoor swimming pool on the roof of a large hotel. There are several Cissus vines hanging in moss baskets and they all have powdery mildew. I have treated them with sulphur dust, but the problem continues.
A. Mildew thrives in a damp place and I am sure that an indoor swimming pool must be very humid. It is extremely difficult to control in any event. Infected plants should be removed to avoid further contamination. I personally think this was not a good choice of plant for the location as these plants are prone to mildew. Perhaps you could recommend that the client replace them with something more appropriate such as ferns.

Q. One of my residential clients has two beautiful Ficus trees direct-planted into decorative containers with drainage. The plants are very potbound, and it is getting harder and harder to keep them sufficiently moist to prevent leaf loss. The client read somewhere that roots can be trimmed and she wants me to do it. Can I trim the roots of a ficus tree with any success?
A. I have had good success with trimming Ficus roots and so have other professionals I know. Do it when the weather is warm but not hot, and do it when the soil is moist but not wet. Trim only the roots which are circling the outside and bottom of the container and do it as quickly as possible. Try not to pull the roots apart; just cut them off using clean scissors. Be sure the new soil is uncontaminated and that the tree is fully watered when you finish. Check it for watering again in about three days.

Q. As far as the health and appearance of a plant are concerned, which watering method is best: subirrigation or drip irrigation? Or, are they both about the same?
A. When it comes to indoor watering systems, my personal preference is for subirrigation in almost any form. However, it really depends on the client’s budget, the interior landscape design, the number of plants, etc. In other words, neither is better or worse than the other; this is an individual choice to be made according to the specific needs of the installation.

Q. I have not been feeling well for several months. I suspect that it is from exposure to pesticides. How can I tell for sure?
A. Contact your local poison control center and ask them to refer you to a physician in your area who specializes in chemical-related illness.

Q. Is there a way to combat fluoride toxicity, especially with Dracaenas? I hear there is no one solution to the problem except using non-fluoridated water, applying lime once a year, or applying dilute solutions of calcium hydroxide.
A. Aside from using non-fluoridated water, the problem cannot be eliminated entirely, and fluoride is more toxic to some plants than others. In most cases it is harmless unless there is already a lot of fluoride built up in the soil. In that case, the plant may be unable to utilize its nutrients because the pH of the soil makes it impossible to do so. This will weaken the plant and contribute to other ailments that afflict foliage. Try to leach plants thoroughly before you install them, and then be sure not to overfertilize on the job. When plants are old and their soil is compacted, transplant them into new soil.

Q. We have a prospective client who has a toddler and she is concerned that he might chew on the plants and become poisoned. I know Dieffenbachias are poisonous but what others should I worry about?
A. Philodendrons and Crotons can be poisonous too, but with toddlers the real problem is usually the soil and not the leaves. The same is true with cats. Both are in more danger from the soil than from the leaves which do have a bitter taste and are not all that pleasant to eat. Toddlers have been known to eat dirt, and plant soil may contain such items as time release fertilizers, systemic insecticides, fungicides, etc., all of which can make a child (or pet) ill.

Q. We are servicing a hotel with an indoor waterfall and pond surrounded by Pothos and Chinese evergreens (Aglaonema) which are on a drip system. They appear to be suffering from soft water damage. There is no alternative source of water for the drip system. What can we do?
A. You can do one of three things: 1) hand water using a non-softened water source (labor-intensive); 2) have a plumber separate the water and divert unsoftened water to the drip system and softened water to the water features (a one time expense but possibly an expensive one); or, 3) have the water softened by a system that does not use cation-exchange methods (the easiest alternative in most cases).

Q. Can I install palms around a low-light, chlorinated pool and hot tub?
A. Yes, if they are not close enough to the water to get splashed. They will benefit from the humidity, but drops on the leaves could cause them to be damaged, or at the very least to look unattractive from hard water spots.

Q. We have always had good luck with Rhapis palms. But recently, two in a client’s executive office have displayed brownish blotches on the leaves. None of us can figure out the cause. Any ideas?
A. Two come to mind: burning from a leaf shine or leaf cleaner, or air pollution. If you recently cleaned the leaves, probably using an alcohol-based cleaner, they could burn. Use only water to clean palm leaves. If you haven’t cleaned the leaves, have there been any changes made to the office? Any major cleaning by a janitorial service? Have you or your technicians ever noticed any unusual odors? Is the office in an area with extremely bad smog? You’ll have to play detective a little while longer or take a sample to a plant pathologist.

Q. Every time we water the hanging moss fern baskets at a restaurant, they drip. Is there anything we can do to prevent this?
A. Moss baskets are usually a poor choice for use indoors, especially in a commercial environment. There is no real solution to the problem. Moss baskets leak. Period. To reduce the amount of leakage, make sure the moss is tightly packed, water them outdoors, water them thoroughly each time, and do not rehang them until they have stopped dripping. It might help to blot them with a towel before rehanging.

Q. Can I install ferns around a low-light, chlorinated pool and hot tub?
A. On the whole, most ferns will do well in such environments as long as they don’t get splashed by the chlorinated water. But, some varieties such as Nephrolepis (e.g., “Boston” or “whitmanii” can be messy and therefore expensive from a maintenance standpoint. On the other hand, ferns such as the Polypodium (“rabbit’s foot fern”) and the Platycerium (“staghorn” and “elkhorn”) are much cleaner choices.

Q. We have three Asplenium (“bird’s nest fern”) in a client’s executive office. They are displaying brownish blotches on the leaves. I cannot determine the cause. Any ideas?
A. Possibly burning from a leaf shine or leaf cleaner, or air pollution. If you recently cleaned the leaves, probably using an alcohol-based cleaner, they could burn. Use only water to clean ferns. Asplenium can also get brown spots if misted in a hot window. Is your client in an area with extremely bad smog? Perhaps with windows open near the ferns? If you cannot discover the cause of the spots, take one of the ferns to a plant pathologist for an evaluation.

Q. When I received some special ordered Cyrtomium (“holly fern”) for a client, many of the leaves were partially black. The grower told me to just cut off the black leaves. I am worried that these plants might have a disease.
A. Actually, I think they were probably cold damaged. In that case, removing the damaged leaves will end the problem, as long as you install them in a location that stays around 60F to 65F.

Q. What can I do to get rid of the weeds growing out of the base of my ferns? They are never there when I buy the plants but appear within a few weeks after installation.
A. Replace the top inch or so of soil with clean soil. That should eliminate the seeds that are in the upper layer of soil and stop the problem.

Q. One of my clients has a gorgeous 12′ Dracaena marginata in his southwest office window. It had mites and mealy when we took over the maintenance. We have removed the plant three times, sprayed it, and even removed the mealy by hand. The plant looks great for a couple months and then the pests return. We can’t move the plant because the client insists that it has always been in that window, etc.
A. Have you thoroughly sprayed the canes and the soil as well as the leaves? Have you tried a soil drench with pesticide? Even if you don’t see them, mites and mealybug can be on the canes and in the soil — even on the pot itself, in the saucer, on the sphagnum moss or bark, etc. If you don’t treat those areas too, they will just repopulate themselves and infest the plant all over again. You may also want to introduce some humidity to the area surrounding the plant — a large pebble tray or perhaps your client would spring for a small humidifier? Most pests like it dry, and some humidity might help deter them.

Q. I recently took over the maintenance of a very large atrium at an airport. There are 47 Dracaena massangeana, all over 7′ tall, and all of the ones on the west side have very dark soft areas in the leaves that eventually dry out. What causes that and how do I treat it?
A. Sounds like heat damage. Are the plants in a warm window? If so, the western exposure could be way too much sun and heat for these plants, which should really be in diffused light.

Q. I maintain a Song of India (Pleomele reflexa) that was once a 10″ gift plant. It has quadrupled in size and is drooping. I have staked it but that really detracts from its appearance. Can I trim it back?
A. Yes, but just the longest canes. Trim it in early spring and fertilize the plant about a week later.

Q. A client of mine has a Beaucarnea in her office and lately I notice that the soil smells rotten when I bend down to water it. I’m thinking someone may have poured something into it, but the plant looks fine otherwise. Anything I should know before I transplant it?
A. Someone may have spilled something into the plant, but that big swelling at the base of the trunk is the plant’s water reservoir, and if the plant has been overwatered to the point where the roots are rotted, that rotting can spread to the reservoir. Once that happens, it is just a matter of time before the trunk collapses, or in some instances bursts open, letting out a putrid odor that spells the end of the plant. I would definitely transplant it into the same size container with fresh soil unless it is potbound, which seems unlikely. These plants cannot afford to retain excess water, so use a potting mix with good drainage.

Q. I hear that Dracaena are susceptible to Erwinia blight. I asked my local suppliers about this and they knew nothing about it. Do all Dracaenas get this blight? Could you describe the symptoms?
A. Erwinia chrysanthemi is commonly called Erwinia blight and it is considered to be the most significant bacterial pathogen of tropical plants. It is found on Dracaenas as well as Aglaonemas, Sansevierias, and Syngoniums. Erwinia carotovora or “rapid decay” is found on Bromeliads, Dracaenas, and Pothos; and E. dieffenbachiae is common to Dieffenbachias. Erwinia is usually found on plants newly arrived from a grower who did not practice proper preventative or cultural growing methods. It would be extremely unlikely to develop on its own at your job site since it requires such a high degree of humidity in order to thrive. The symptoms vary depending on the species afflicted. For the most part, the disease is characterized by dark to black leaf spots with yellow or necrotic haloes around them. In advanced cases the leaves may wilt, yellow, discolor, or turn mushy, and the plant structures may collapse. If you suspect that your newly-installed plants are suffering from this disease, you should contact the grower immediately.

Q. I keep hearing how the Aspidistra is supposed to be so hardy, but I stopped using it because it always seems to die on me. The leaves all wilt over and collapse at the soil level.
A. Unless they have a disease, this sounds like you are overwatering in a cool location. Cut back on the watering, and they should stop collapsing.

Q. When I buy Massangeanas at my local nursery the pots seem so tiny in comparison to the size of the plant. Should I pot them up a size before installing them?
A. Absolutely. It is far easier to pot up anywhere but on the job site. Spec your decorative containers a little larger too if you are going to continue to purchase plants that must be potted up.

Q. My client brings in plants from her deck and puts them in the house. In a pot that contains a small Beaucarnea there are earwigs and sowbugs. I don’t know how to control them indoors.
A. Take the plant back outside and flush it out thoroughly. The passengers should abandon ship quite readily. Make sure the pot is drained thoroughly. Return it inside to a warm and dry location, and do not water it again until it is almost completely dried out.

Q. Is there a way to combat fluoride toxicity, especially with Dracaenas? I hear there is no one solution to the problem except using non-fluoridated water, applying lime once a year, or applying dilute solutions of calcium hydroxide.
A. Aside from using non-fluoridated water, the problem cannot be eliminated entirely, and fluoride is more toxic to some plants than others. In most cases, it is harmless unless there is already a lot of fluoride built up in the soil. In that case, the plant may be unable to utilize its nutrients because the pH of the soil makes it impossible to do so. This will weaken the plant and contribute to other ailments that afflict foliage. Try to leach plants thoroughly before you install them, and then be sure not to overfertilize on the job. When plants are old and their soil is compacted, transplant them into new soil.

Q. We installed over 100 Aspidistra beneath some large palms in an atrium about 12 years ago. The Aspidistras have grown considerably and were always healthy until just a few months ago when they began to exhibit yellowing of the leaf edges which has become worse.
A. I believe this is probably a magnesium deficiency. Check your fertilization records to see if these plants are receiving sufficient macronutrients, which would include magnesium, and that they are not being leached out of the soil. If feeding them does not stop the problem, you may want to apply a light dilution of Epsom salts to the Aspidistras, as that contains magnesium in a sulphate form that the plants can absorb.

Q. I maintain a small but very warm and brightly lit atrium in an office building. It has three huge Dracaena cordyline that are constantly infested with mites, sometimes with aphids too. They are planted in large stationery planters, so I can’t remove them to spray. We have been spraying on weekends when no one is around. Nothing seems to work because they seem fine for a short while and then they are infested again.
A. There can be a variety of reasons why these pests keep returning. For example, do you rotate the pesticides you use? If not, that would explain their resistance to your spraying efforts. Are the plants under stress from underwatering? If so, you need to ensure that they are kept evenly moist, which will reduce the stress and also increase the humidity in the environment, which in turn should make it less hospitable to these pests.

Q. I was very surprised to find that two Dracaena massangeana at one of my maintenance accounts were blooming. Very fragrant, not much to look at. Is there any harm in allowing them to bloom this way? Why did some bloom and not others?
A. It can cause the crown to lose its symmetry, so the usual rule of thumb is to remove the very first sign of a flower. The blooming occurs when the plant has been subjected to a period of very cool temperatures, sending the plant a message to put out a flower.