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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have an unusual request. What flower can I use to demonstrate the use of food coloring to bring beautiful color to an ordinary bloom? Do you know the method for doing this? I want to photograph the progress to show how something unattractive and ordinary can become beautiful. I plan to use the demonstration to show people that they have beauty inside. (e-mail reference)

A: I popped your question to Barb Laschkewitsch. Barb is a former florist and our floral design instructor on campus. She suggests taking a flower, such as a white carnation, and not giving it water for about a day. Add the desired food coloring to the water and place the carnation in it to so it will take up the water. The flower should turn the color you want. I hope this solves your dilemma.

Q: I enjoy reading your column in our paper and try to listen to you on the Hear it Now radio program as often as I can. I even spoke to you once on the radio show. I have a question about our cotoneaster. We think it may have fire blight. I have read that the remedy is pruning the shrub. How severe do we prune? Does it need to be pruned before it buds out? Do we need to treat it with any sort of chemical? I have attached some pictures. Thanks for any help you might be able to offer. (e-mail reference)

A: Thanks for being a fan of the Hear It Now radio program. From the photos, I cannot tell for certain that the symptoms are fire blight. Cotoneasters benefit from a coppicing, which means cutting down the plant to the nubs of the stems to get a fresh flush of growth. Give the plant a hard pruning before new growth begins. After that, stand back and watch new growth flourish. No chemicals need to be used. Clean up all the debris from the pruning and monitor the new growth.

Q: I have had a hibiscus for many years. The leaves on one of the stems are turning brown from the edge of the leaf toward the center and have a yellow outline. The plant also has some sticky material on it. However, the plant is blooming and seems to be growing; I am not giving it too much or too little water, and I use a time-release fertilizer in the fall when I bring it inside for the winter. It gets plenty of sunlight. Is there something wrong with the plant or is it molting its old leaves? Thank you for your help. (e-mail reference)

A: The fringe browning on some of the foliage could be due to salt accumulation in the soil. If you have a water softener in your house and are using that water for the plant, that could be a major source of salt. Salts in the fertilizer also could be a problem. Not having good pot drainage could cause problems. The stickiness you describe probably is caused by scale insects or spider mites multiplying on the stems, flowers or leaves. Both often multiply unchecked after plants are brought indoors for the winter. I suggest repotting using fresh potting soil. Use a new or cleaned container that drains well. Also, cut the plant back heavily to get regrowth that would be better looking than the droopy foliage describe. You didn’t say where it is you live. The hibiscus would benefit from a little exposure to cold, but not subfreezing temperatures. However, you don’t want the plant to get cold enough that it goes dormant. I’m assuming your plant it is not the tropical variety. The cold will provide a little environmental variance that usually results in the plant becoming reinvigorated and producing more blooms.

Q: I’m wondering if you can help me with the name of my nanna’s grapevine that used to grow in her backyard in Newcastle N.S.W. The bunches were small and had burgundy and green grapes. We did not eat the green grapes. I remember the vine had a beautiful, old-fashioned woman’s name, but I can’t remember what it was. I hope you can help. Can you tell me where I could buy one? (e-mail reference)

A: I am at a loss as to where N.S.W. is. However, I figure it must be in Australia somewhere, judging from your e-mail address. What it could be is a seedling that got started from one of the fine domestic wine grape growers in your country. I can’t venture a guess as to what it is because your grape varieties are different than what we grow in the U.S. I suggest that you contact a grape grower near you to see if he or she can help you identify the variety.

Q: We planted an oak tree seedling (wedding favor) at our new house. What is the best way to ensure that my oak tree survives? How often should I water it? We put a layer of mulch around it. This tree has a lot of meaning to me, so I want to make sure that it lives a long life. Thank you! (e-mail reference)

A: You’ve done everything right so far. Keep the mulch (wood, I hope) from resting up against the small tree because it tends to encourage decay. Your biggest concern for the next couple of years is going to be the grazers, such as mice and rabbits. You can do this by putting a fine wire mesh (hardware cloth) around and over the tree. Depending on the determination of your nibblers, you might want to add another layer of protection by applying a repellent. Several are on the market that have equal effectiveness. Oaks don’t need a lot of watering once they mature. During the next three years, you should check the moisture content of the soil under the mulch before watering. Poke your fingers into the soil. If it feels moist, don’t water. When you do water, give the tree a good soaking each time. If you follow this general advice and use some common sense, with a shot of luck thrown in, this tree will surpass our lifetime.

Q: I have a neighbor who cut quite a few large branches off his tree. The branches fell in our backyard. I happened to look outside yesterday in the rain and saw that one of the braches had bloomed flowers. I was wondering if there is any way I could save it or plant it. I would so appreciate your expertise on this as soon as you can. I hope I can keep it alive. (e-mail reference)

A: Don’t hope too much because it won’t happen. Enjoy the branches in flower by sticking them in water and then dispose of them as you see fit. Sorry.

Q: Our silver maple has a root that is curling around the tree near the surface. An arborist told me that I should cut the root off. However, he neglected to tell me about any special measures I should take in cutting it and how I should treat the cut end of the root. Do you have any suggestions? (e-mail reference)

A: The advice the arborist gave you was correct. The root needs to be cut back at the source or as far back as practical. You can do this with a hammer and chisel or a pruning saw. If you use a saw, replace the blade or at least sharpen it. Once a clean cut has been made, no further treatment is needed. The wound will heal itself without any interference from you.

Q: I scrolled through your list of ficus questions, but I couldn’t locate a match. My ficus is very sparse and has had considerable leaf drop and yellow leaves. There is a very small black and gray pest on the undersides of the leaves. There also are small spots of almost shiny black excrement. Do you know what this might be? (e-mail reference)

A: From your description, this sounds like a scale insect infestation because these insects typically attach themselves to the undersides of leaves and cause the damage you describe. I would encourage you to visit local garden stores or greenhouses in the business of selling houseplants to find an insecticide that you could use. This likely would be a systemic insecticide that would be applied to the soil and taken up through the roots and then throughout the plant. There also is a product called Neem Oil that is safe to use directly on the foliage. Be sure to follow the label directions. The Neem Oil would be the safer treatment to use. However, a very sparse ficus probably won’t recover, so you might be better off dumping the plant and starting again with a fresh, healthy plant rather than going through the frustrations of trying to resurrect something that never will meet your expectations.

Q: I have three cedar trees that have been growing for years next to an old pond. Two years ago, we did some digging in the pond, so the roots of the trees ended up near the water’s edge. The trees were fine until a hot week in August. In one week, the trees turned completely brown. Are they dead or should I wait and see if they turn green again? (e-mail reference)

A: They probably are dead. However, I would suggest waiting to remove them in case they are not dead. A few months of time invested might save you a lot of work.

Q: As you are the most knowledgeable I found on the Web regarding cottonwoods, maybe you could answer my questions. We have an old and tall black cottonwood that was struck by minus 15-degree temperatures in 2009. After that, the leaves turned yellow or fell off. The next spring, only 5 percent of the tree had leaves. Is this a permanent dieback or can the tree use the old xylem to regenerate its cambium? (e-mail reference)

A: I suspect that you are writing from the mountains of the West Coast. This was a nasty blow to the tree by Mother Nature. It is very likely done for if only 5 percent of the branches have sprouted foliage. To be on the safe side, I suggest that you contact a local International Society of Arboriculture certified arborist to inspect the tree and see if there is any chance of it recovering. If not, then plan and budget to have the tree removed for safety reasons. Go to to find an arborist in your area. Be sure to check credentials and insurance before allowing any major work on the tree.

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

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