Landscape Q&A

by Joelle Steele

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 This column is no longer active as of March 2021, but you can browse it to possibly find answers to your questions.

Q. It gets super hot in summer where I work, and that’s when clients want everything planted. I’d like to wait until early fall to avoid plant loss from heat in landscapes I don’t maintain. Should I modify my guarantee or refuse to plant until fall?
A. How about modifying your guarantee to say that you have only a limited replacement guarantee on plants you do not maintain when it comes to ones installed during hot weather against your better judgment and that the client doesn’t water correctly or enough. You can add language to define what constitutes hot weather and how much watering should be done to avoid the losses in the first place.

Q. When is the best time to turn off a sprinkler system for winter in a snowy area?
A. As soon as the ground starts to freeze, turn it off. If you have a back drain, you should drain the lines before the first heavy frosts to avoid damage to the system.

Q. I want to remove a lawn that is mostly Bermuda grass with weeds. Once I cut the sod out (the roots of the grass and weeds) can I then reseed the area without fear that the old stuff will grow back?
A. For better results, I would use an herbicide first and kill the grass and weeds. After everything is dead, then I would remove the sod and weed layer, cover the area with fresh soil, and then reseed.

Q. For three years, I have been maintaining two lilac trees for a client. They appear to be very healthy but they do not bloom. I have limited experience with these plants. What am I doing wrong?
A. It could be any number of reasons. Most lilacs prefer nice cold winters followed by growing seasons that provide at least 6 hours of full sun daily. Lack of sun is the most common reason for not blooming. Lilacs should not be planted too deeply, and they prefer an alkaline soil. If they are planted near azaleas or a lawn, they may be receiving too much acid or too much nitrogen. You shouldn’t need to fertilize them, but if you do, fish emulsion and bone are good organic foods. Lilacs set their buds on the old growth, so don’t prune them any later than July or you’ll destroy their future flowers.

Q. How do I get rid of small wasps living in a corner of the moss of my staghorn fern without getting stung and without damaging the fern?
A. I don’t have any experience with this, but I would probably start by spraying the waspy area of the moss with a regular wasp spray, towards evening when the insects are less active. It might take a few sprays every couple of days to get them under control. Then I would submerge the stag in a 30% or less dilution of insecticide to kill off any live larvae that might still be in the nest.

Q. I am new to the landscape business, and I have been using an herbicide for weed control for the last two years in order to avoid the labor of weeding. But there is still so much weeding to do. Is there a better way to handle this problem?
A. In addition to herbicides, you can also use pre-emergents to stop weeds from growing in the first place. But, pre-emergents stop all kinds of seeds from sprouting, so only use them away from any recently seeded areas

Q. I recently relocated to Michigan from Georgia. I am re-starting my landscape and lawn business here, and I have been hired to install a new lawn, but I don’t recognize any of the grasses grown in this area. Is there anything I need to know?
A. The grasses you are likely to find in Michigan will be cool climate grasses, such as bluegrass, fescues, and rye. These grasses are more sensitive to disease and pests than the warm climate grasses you are used to in the southeast. They are maintained in much the same way, but the cool grasses do not fare as well when the weather is warm, and so they need more attention during summer heat waves.

Q. Are there any rules for setting sprinkler times for lawns?
A. In general, water the lawn just before sunrise. This allows the water to soak in before the warmth of the day can cause it to evaporate. Because every grass and every soil is different, you should monitor the first few waterings to be sure that each area is getting sufficiently saturated, but without any water pooling/puddling or running off onto paved surfaces. As for frequency, once a day should be sufficient, but at some times of the year you may need to water only a couple times a week. This is something you have to experiment with for each landscape.

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. Is it better to buy roses bare-root in winter and plant them, or wait until spring and buy them in pots?
A. I usually recommend bare-root because the plant has more time to establish itself, and also bare root is less expensive than potted roses. But, if you aren’t sure what the rose will look like or what its growing pattern will be, you should probably buy potted.

Q. I live in southern Oregon. Can I relocate a Japanese maple in my yard at this time of year (early fall)? If yes, what is the best way to do it?
A. Yes, you can move it. Be careful when you dig it up so that you do as little damage to the roots as possible (although I have root-trimmed them at this time of year with no problem). Dig the new hole at least twice as big as the root ball, fill the hole with water and let it sink in. Add some soil, place the tree in the hole, add soil around it, add more water and let it sink in again, finish adding soil, water it again, cover the soil with some bark, and you’re done. Keep it watered regularly until the fall rains come.

Q. I have a potted staghorn with large upright leaves that are starting to fold and turn downward. The shield fronds seem fine and are firm. Is this natural or could I be overwatering?
A. In general, when the leaves get very large they can droop from their own weight. I prefer to let a stag go almost dry between waterings, but it depends on how much light and heat it gets during the course of a day. Hard for me to tell about watering issues without seeing a plant in person.

Q. What is the difference between bulbs and corms?
A. Aside from their appearance, the main difference is how they use the food that is stored in them. The bulb uses and then replenishes its food resources every year. The corm uses up all its food resources and turns into a dry husk, then grows a whole new corm in its place.

Q. We just took over maintenance of a small yard enclosed by a very mature but ugly Eugenia hedge that’s been boxed to death. Can it be salvaged? Any advice on how to start?
A. It could take just as long to make it look good again as it would to install new plants and train them into a hedge. If you opt to salvage it, start by pruning the top so that it is narrower than the base, and so that the top is rounded or slightly pointed. You will need to remove about 10″-12.” It will probably take a couple years to look good, but a new hedge would take at least three years to reach a mature size.

Q. My staghorn fern has yellow leaves. What could be causing this?
A. If the leaves are yellow from the center outwards it is probably being overwatered, is too cold, or both. If the leaves are yellow from the tips inward, then it is probably underwatered. Be sure that you thoroughly drench the staghorn by submerging the board and moss in a large tub or bucket of water. Then allow it to dry out almost entirely before drenching it again. If the weather or the room are very warm, move it to a cooler location. If it is in a cold location, move it to a warmer one. It should be in partial shade, not full sun or full shade.

Q. We have a pond with water plants in it. The pond company sold us snails to keep the algae down, but the snails eat the plants and multiply like crazy. I don’t know if this is in your area of expertise, but can you tell us how to eliminate algae and still have plants?
A. Aquatic ponds require a balance of plants and animals to be healthy. Snails are part of that balance. You need to have the type of snails that do not eat plants and eat only algae. Two of those are Neritina reclivata (Olive Nerites) and Viviparis malleatus (Japanese or Trap Door Periwinkles). It is unlikely that either of these will over-multiply, and you will probably have to buy more of them if they die off due to not having enough algae, as is the case with some ponds.

Q. How can I eliminate scale from my staghorn fern (Platycerium). I’ve tried alcohol on a Q-tip and they just come back.
A. You are only killing the adults and not the eggs and immature adults that are still in the moss and that are too small to see with the naked eye. Drench the staghorn in water until there are no air bubbles. Remove the stag. Put on gloves and add pesticide to the water at about half-strength. Drench the stag for about five minutes. Remove it and hang it up to dry. In about a week or so, right before it is totally dry, repeat the entire process. Also, treat any neighboring plants that have scale.

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. I have what appears to be a fungus on some large staghorn ferns (Platycerium). What can I do to get rid of it?
A. You need to be sure it really is a fungus. These ferns get a soft white downy underside to their fronds and to the flat leaves that cover the moss. It’s not a fungus. But, if there really is a fungus and the ferns are planted/mounted on a moss-covered board, let the moss dry out fully between waterings and that should kill any fungi or pests. If there is definitely a fungus on the moss or board, you can soak the board/moss or pot in a big pan or bucket or bathtub filled with an extremely mild dilution of fungicide and water. Don’t get the leaves wet with the fungicide unless you hose them off with water before you put them back in their original location. If they are potted and are rootbound, you may also need to transplant them into fresh soil or onto a moss board.

Q. My neighbor planted a 10′ tall Ficus benjamina only 8′ away from our fence. I’m afraid that the roots of the tree will damage our fence some day.
A. At that distance, the Ficus should not produce roots sufficient to destroy the fence.

Q. I live in Santa Barbara, California and I have been told that I have the “giant” whitefly devastating my Hibiscus and my lemon tree. My plants look terrible and I don’t know how to get rid of this pest. Nothing seems to work.
A. The giant whitefly comes from Mexico. You have to take preventative action and also take immediate action against new infestations. Hose down your plants very thoroughly with a strong stream of water being sure to get the undersides of the leaves. Introduce beneficial insects such as parasitic wasps and ladybugs, which are natural enemies of whitefly. Hang those sticky yellow plant strips above or next to the plants. Control ants around the plants. There is a chemical called imidicloprid (sold as ImidiPro) that is supposed to be low in toxicity and is applied as a drench to the roots, which absorb it into the plant to be sucked up by the whitefly.

Q. After wintering my Ficus tree indoors, I put it outside and it now has these thin white tubes sticking out of the trunk. I have removed them but they keep returning.
A. When this question first arrived, accompanied by a photograph, I thought the white tubes were aerial roots of some kind, although I had no idea why the tree was producing them. However, as it turns out, they were the product of Asian ambrosia beetles. I include this information so that anyone reading this column will know what the growths were.

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. I purchased some Indian Laurels (Ficus retusa nitida) and planted them where the soil has some clay in it. I watered them daily until the rainy season came. About a month later, they appeared to be dead, all the leaves dried and curled up and fell off. The branches are all stiff and brittle now. What went wrong?
A. You overwatered your trees and the roots either rotted or succumbed to a fungus from being too wet. Clay soil retains moisture, and you should not have watered these trees more than one good soaking a week for the first six months. After that, one good soaking a month should be enough for about another six months to a year. If you replace the trees, do not plant them in the same place in case there is still fungus in the soil.

Q. I have a staghorn fern (Platycerium) on a patio at a residential account. It is always very dry between visits and looks kind of droopy with some tipping. It gets partial sun throughout the day. Should I move it to a shadier location.
A. I wouldn’t. The Platycerium species generally need good light. You are in a warm climate, however, and that may be why the moss dries out so quickly. Or the stag may need to be transplanted onto a bigger base with new moss. Or, when you water it you might not be getting it wet enough throughout the moss. If soaking is an option, you might want to do that instead of just spraying it down with water.

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. 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. 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. The green leaves on my Platycerium (“staghorn”) keep falling off. I don’t let it dry out, so I don’t think that’s the problem. What do you think?
A. I think you are probably overwatering. Staghorns should be almost completely dry between waterings. This will prevent leaf loss and will also ensure that pests cannot get a foothold in the sphagnum moss.

Q. I maintain a tree fern on a small enclosed deck. The new growth always looks fine, but with every new frond an old frond dies, so the plant grows taller but is never any fuller. What can I do to stop the leaf loss?
A. Tree ferns need very good drainage and a fair amount of humidity. I am assuming that since this fern is on a deck that it is also in a container. First, make sure it is not in direct sun. If it is, move it to the shade or into diffused light. Second, check if it is rootbound. If so, trim the roots slightly and then return it to the same pot with fresh soil: half loam, one-fourth peat, and one-fourth sand. If possible, you might want to place the pot on a pebble tray filled with water to increase the humidity. A light misting might also be helpful.