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Ron Smith answers questions about flowers, trees, gardens and shrubs.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I planted a fruitless cherry tree several years ago. It lived up to its name for five years, but now it is producing many cherries. Can I eat them? (California)

A: Give them a taste to see if they are palatable. If not, then forget it. I would encourage you to find out just what variety of cherry tree you have before tackling the eating part. Cherry pits, leaves and stems are poisonous, so don’t include any of those in your diet.

Q: I understand it’s difficult, if not impossible, to anticipate with any accuracy when and how heavily a cottonwood tree will drop its debris. I’ve heard that rain and snow amounts are factors. We have a large, old cottonwood next to our house. Every year it drops vast amounts of cotton debris over our house and surrounding areas. It might be dying because the last few years it seems to be dropping less. We’re planning to have our house painted in the next few months. Do weather patterns result in an early or late cotton debris season? We had an unusually heavy amount of snow this past winter. Thanks for any information you can offer. (email reference)

A: Good question, but I don’t know the answer. Extremely low temperatures can affect the flower buds on any tree. I wouldn’t count on the cotton count to be nonexistent or low if you are planning to paint your house this summer. I would suggest that you wait until after the cotton dropping season passes before doing the painting. You might want to check with Gary Johnson, urban forester at the University of Minnesota, to see if he can better advise you on this subject. He is getting a copy of this email and may respond to you directly. If not, you can get in touch with him at

Q: First of all, I love your website! It's been a tremendous reference for me. My question is about the proper classification of arborvitae. Is it considered a tree or a shrub? I ask less from a scientific viewpoint than I do a popular perception. Our property contains an easement for a natural gas line. Our easement contract states that no trees may be planted within 20 feet of the line. However, shrubs and bushes are acceptable. Obviously, the gas company is concerned with the deep roots of a tree damaging the gas line. I've always heard people reference arborvitae as a shrub. Do you believe that I could plant arborvitae without fear of damage to the underground utilities? If you advise against them and if they are truly trees, would you have any other recommendation that might be suitable for privacy? Thanks in advance for any assistance. (email reference)

A: Thanks for the very nice compliment. It is greatly appreciated. The arborvitae (Thuja species) is an evergreen plant classification that includes small, medium and large trees. You could get some that would stay under 20 feet and not be a problem with gas or overhead lines. Some cultivars will reach 80 feet. It all depends on where you live and what is available on the retail market. For example, if you live in the northern region of the country (zones 3, 4, 5 and possibly 6), the Brandon, emerald and techny cultivars will stay under 20 feet and might be considered a medium shrub. In the end, it all depends on what the gas easement folks call a tree or shrub as to whether you can plant any of these cultivars. If you want, you can use my comments as an authoritative source.

Q: I have been reading your website and it is clear that you are the person to fix my problem. We bought a house 13 years ago with a mature weeping birch in the front yard. It is a beautiful tree. However, we soon discovered that it had a few problems. Some kind of sticky substance falls from it in the spring and summer. It coats the patio and smothers the leaves of any garden plants near the tree. The leaves of the tree turn yellow and fall off all summer long. Also, the trunk and branches are covered with lichen and moss, despite its southern exposure and good air circulation. These issues have worsened through the years, so we are considering removing it. Is this our only option or is there anything else we can do? (Vancouver Island, Canada)

A: The tree might be salvageable, but it all depends on the extent of what I believe to be some kind of scale infestation. You should contact an International Society of Arboriculture certified arborist to inspect the tree. It may take some pruning and an injection of a systemic insecticide to kill off whatever is feeding and slowly killing this magnificent tree. Go to to locate qualified companies or individuals in your area. Try this before opting to have the tree taken down. The ISA folks are tree professionals. If they can save the tree, they will.

Q: I need to move some rhubarb plants but they have leafed out. The plants are no longer producing very well, but I wanted to give them a fresh start in another location in my garden. Can I safely move them? (email reference)

A: If there is a genuine need to move them, you don't have much choice in the matter. If you can, wait until a cloudy, cool, drizzly day is in the forecast. Move them the night before and water in well. There is at least a 50 percent chance some of them will survive.

Q: I live about 40 miles west of New York City. I have a beautiful silver maple in my backyard. I want to put a patio in, but I am concerned about damaging the tree if some of the roots are cut. The drip line is approximately 15 feet from the trunk. The patio will be in a small section of the drip line. Is there a rule of thumb that I can use? At what size will a cut root not regenerate? Any assistance is appreciated. (email reference)

A: You should be safe at the fringe of the drip line. The large, roughly wrist-sized roots usually will not regenerate. However, the limited area you will be affecting should not hurt the tree.

Q: My lawn was heavily damaged by voles last winter. Should I rake the runs and patches of shredded grass or just leave it? Does it really make a huge difference either way? (email reference)

A: Funny thing about turfgrass. If you do nothing, it will grow. If you do something, such as rake, fertilize or water, it will grow much better. It all depends on your visual tolerance level. Some folks are happy with keeping whatever grows, while others almost go into anaphylactic shock with the slightest discoloration of a few blades of grass. It depends on how much work you want to do.

Q: I have a client who has a cotoneaster hedge. He is asking about using a combination of lime and sulfur to stop fire blight. Will it work, and is there a product that he can purchase that is ready to spray on the hedge? (email reference)

A: Cotoneaster hedges are susceptible to fire blight. There are several approaches in controlling this disease. Do not overstimulate the plant by fertilizing. Soft, succulent growth is the most vulnerable to this bacterium. Try to increase the amount of sunlight and air circulation to the planting if possible. A Bordeaux mixture (copper and lime combination) does an acceptable job of controlling fire blight. Streptomycin also is used but is more expensive and increasingly difficult to find on the market. Make sure that label directions are followed.

Q: I always thought that when planting a rhizome, it should be covered with a thin layer of dirt until the roots are established. After that, the rhizome tops should be uncovered to prevent rot. It sometimes dips below 30 degrees here in West Virginia. What do you think about uncovering the rhizome? Also, I have had a wisteria vine growing on the edge of my woods for about eight years. Although it has many long vines and greenery, it never has bloomed. I have tried leaving it alone, trimming it back and once used a fertilizer that was meant for blooming plants. Do you have any idea why it doesn't bloom? (email reference)

A: Your questions can be answer better by local West Virginia Extension Service personnel. To locate an agent in your state, go to If your attempt to get local assistance is not satisfactory for any reason, please get back to me.

Q: I hope you can help me figure out what to do with my apricot tree. When we moved to this house, the apricot tree in the yard had tons of fruit. However, it has been four years since it had fruit. Meanwhile, my mom's tree is full and has fruit. Is my tree dying? What can I do? The nursery people around here don't seem to have any helpful advice. My cousin, who is a fantastic gardener, says I should hit it with a sledgehammer. Thanks for any advice. (San Diego, Calif.)

A: What is hitting it with a sledgehammer supposed to do? It certainly will not be good for the tree! If the branches are mostly bare, then there isn’t any hope. Apricots are the moodiest fruit-bearing trees I know of. They may have heavy fruit one year and then nothing for many years. I don’t know how orchard growers make a living growing apricots. I’ve not heard of consistent success from anyone who has written me. The bare branches might be from bark beetle or borer activity. Check around the bare branches to see if there are small holes. If so, that’s a good indication that the tree is on its way out.

Q: I hope to get a more complete answer to my red maple question, even though I have searched the Web extensively. I bought the maple in Kansas City last September. The approximately 6-foot-tall tree was beautiful. I got it at a 25 percent clearance price at the end of the year. I dug a good-sized hole and then filled it with a bag of garden soil and a bit of the old soil. I watered it regularly through September. During October and November, it looked beautiful. It held its leaves a remarkably long time (January). However, I have a bare tree this year. I see that there are small growths at the ends of some branches. These branches are dead and snap off. The rest of the tree looks like it is dormant. To find an answer, I began to search the Web. The answer I got repeatedly was to scrape a branch. If it's green under the bark, then the tree is alive. I went out and paired down all the little sucker branches. They had green under the branches. However, I sense that things are not OK. At the end of the branches, I have little, semiformed buds that do not appear anywhere near developing into leaves. So I have a tree with some branches that are not dead. What does that mean? Is it a goner? I have to believe that it is. Could you expand on the scratch-the-bark answer? I would stick with the tree if there was a reason to believe. (email reference)

A: Glad you asked this question. I hope everybody reads my response. Red maple is a very beautiful tree. I have no doubt that the specimen you purchased was everything you said it was. However, the fact that the tree held leaves going into winter conditions is a very strong indication that the tree was not from a Kansas City area wholesale nursery. Very likely, it came from a nursery further south where the length of day and other climatic conditions are significantly different from those of Kansas City. National chains, such as the one you shopped at, make every effort to purchase high-quality nursery stock at the best price possible. Naturally, nurseries want to sell to these chain stores to move inventory in mega amounts. In some locations, the cultivar of red maple you purchased would be perfect. In cases such as yours, not so perfect. Another point needs to be made. Your overly conscientious attention to the tree’s watering needs probably contributed to the funk the tree is in. You did not allow it to harden off (move into dormancy sufficiently) to tolerate winter conditions. To assign human terminology, the tree is confused. The tree probably is not completely dead. Will it recover and become the beautiful tree you purchased last fall? I don’t think so. You are better off replacing the tree. I hope this addresses your concerns. If not, please get back to me.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail

NDSU Agriculture Communication – May 24, 2011

Source:Ron Smith, (701) 231-7123,
Editor:Rich Mattern, (701) 231-6136,
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