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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I would really appreciate your help with a columnea plant. Most of the plant is in beautiful condition. However, some of the stems contain leaves that have yellowed and have translucent spots. These yellowing leaves are at the middle of the stem. The leaves above and below on the same stem are green. (New Zealand)

A: Perhaps not enough water? Is the air too dry? Check for any insect activity or spider mites. Try spraying the plant with distilled water. This also could be due to normal senescence of older foliage. Sorry I can't give you more specifics. Without seeing the plant and having more information, this is the best I can do.

Q: I went out today to find my dogwood tree falling over. Upon closer inspection, something gnawed the trunk at the soil line until the tree fell. What would have chewed through our lovely dogwood and not damaged the foliage or branches? One week before this incident, we planted several nadina. A day or two later, we noticed them falling over. Something had eaten the roots and gnawed at the trunk of the bush but did not go all the way through to cut off the upper portion. However, there was enough damage to kill the bush. Could this second incident also be related to the dogwood tree falling over? (e-mail reference)

A: The leading suspects on my list would be beavers, woodchucks and rabbits. All are incurable gnawers.

Q: I will have to remove two paper birch trees on my boulevard because both are dying. How close can I plant new trees to the ground-out stumps? I would like to plant prairie dream paper birches as close as possible to the stumps. Is this advisable? (Portland, N.D.)

A: It is very advisable, so go for it. However, don't leave an excess of sawdust at the planting site.

Q: I am looking for a good cherry tree for our area. I am considering the evans bali, meteor or the northstar. I would like one for canning and possible fresh eating. I also have been researching some of the romance series cherry trees available from the University of Saskatchewan. I am particularly interested in the crimson passion or the cupid. I have been trying to find out if and when they will be available in the U.S. I had two lapins that looked nice after I planted them, but they have yet to bud this year and don't look good at all. Fingers are still crossed! I have another question about the evans bali. From my research, all available bali cherry trees are grafted onto mazzard rootstock. Can you tell me why this is done and if it affects the hardiness of the tree? My opinion is that it reduces suckering, which then allows the nurseries to "corner" the market. (Bismarck, N.D.)

A: My guess on the grafting of the bali to the mazzard is the dependable hardiness of the species, although the bali is a very hardy tree. The grafting could be done to give the tree more vigor, but I'm not sure. Both are hardy enough to withstand whatever weather Bismarck can throw at it. I'm sorry, but I don't have an answer for the availability of the crimson passion or cupid cherry. As for meteor or northstar, the choice is yours to make. Both are excellent introductions that have been around for a while.

Q: We planted a young cherry tree a couple of years ago. It died from some parasite because there were sort of leechlike looking things at the base of it. We replaced it with an ornamental plum and want to make sure we do everything right. In case we were guilty of over or under watering the cherry, I am trying to find out about the proper watering of the plum tree. (Connecticut)

A: Daily watering is too much. When you plunge your fingers into the soil around the base of the plant three days after watering it and it is still moist, you don't need to water. Wait another three days and do the same thing. If no or very little moisture is detected, then give the plant a good soaking. You will have to adjust your watering based on the weather conditions and the advancing maturity of your tree. After the second year in the landscape, the tree should not need more than just an occasional soaking during extended periods of heat and drought (two weeks or more). From what you stated, it sounds like your tree was killed off by borers. This pest is attracted to trees that are stressed by over or underwatering, planted too deeply or impacted by herbicide applications to turf areas.

Q: I have a honey crisp tree in my backyard that I purchased a few years ago. It had quite a few blooms on it when I bought it at the nursery. However, it only had a couple of blooms on it the next year and has had no blooms since then. Is there anything I can do to encourage blooming? (Fargo, N.D.)

A: We also have a honey crisp in our backyard that has yet to bloom. Perhaps, after this current rain, some will show up. I think you're a little too anxious to see the flowers. However, if the tree doesn't flower for you this spring or does so very sparsely, take a straightedge spade and push it into the soil around the drip line of the tree. Try six or seven spots. This will cut some of the roots, which will stress the tree enough to bring it into the reproductive cycle. The tree probably is growing lushly from the lawn fertilizer you are applying. This is too much nitrogen and keeps the tree in the vegetative stage.

Q: I have a very large treeless front yard, so I’m planning to plant two trees that get really big and grow fast. I have narrowed it down to red maples and thornless honey locusts. I really like both trees. I have read many of the facts on your website about the red maple. Can you give me some facts on the honey locust? We have clay soil, but everything I have planted is doing well. (Somerville, Tenn.)

A: You really couldn't go wrong with either tree if you buy them from a locally nursery. Avoid the temptation to go to the national chains. There are characteristics to like about both trees. Both are relatively fast growing and have nice, full canopies. The thornless honey locust will cast a dappled shade, which will allow turfgrass to grow normally beneath it. The honey locust also will have yellow fall color in contrast to the red foliage of the maple in the autumn. A plus for the locust is when the leaves drop, they tend to disintegrate. This eliminates almost all leaf cleanup or at least greatly reduces it. Both do well in clay soil if they are not overwatered. In the interest of plant diversity, I encourage you to select a good cultivar of each species for your property. That way, you also can enjoy the uniqueness of both.

Q: I have a 7-year-old pink dogwood that did not flower this year. However, its leaves are out and seem healthy, but no pink flowers. We had a lot snow this winter and a wet spring. In recent years, it did flower. (e-mail reference)

A: Pink flowering dogwood is more sensitive to winter temperatures than the white flowering forms. The first to reflect winter injury are the flower buds because they are less hardy than the leaf buds. This is my best guess at this point. Given a more normal winter, the tree should flower for you next spring.

Q: We have not tested our soil but have been told it is on the alkali side. We have about 200 feet of property line where we want to put up a privacy hedge. However, we are having a tough time finding a suitable candidate that will grow well in our soil and is fast-growing. Any suggestions will be helpful. (West Fargo, N.D.)

A: The Brandon arborvitae is a good candidate if you want a complete screen throughout the year. Otherwise, a lilac, cotoneaster or viburnum hedge would do the trick.

Q: I planted some flower seeds in the house. I have been keeping the soil moist and not letting it dry out. Now I see these little flies all around the pots. Where do they come from and how can I get rid of them? I used Miracle-Gro potting soil. Could they have been in the potting soil? (e-mail reference)

A: These likely are fungus gnats. They are annoying but not harmful. They originated in the organic matter in the soil and from you keeping the soil continuously moist. They love it! You can catch them with yellow sticky traps or spray them when they are flying around with a pyrethrum spray. It will knock them down instantly. Not doing something to control them will result in a continuation of their population until you move them outdoors.

Q: I was harvesting some rhubarb stalks a few weeks ago. When I pulled on a few, two or three other stalks would come out with the one I pulled. It seemed like part of the crown came with them. This didn't happen the two previous years I harvested. I'm scared that the crown has been damaged somehow because nothing seems to be growing in the places where this happened. Please help because people rely on my rhubarb jam. (e-mail reference)

A: Any kind of harvesting does some damage to the plant. It will recover unless your plant is being overharvested or is in poorly draining soil that is remaining too wet for too long. Generally, harvest about 30 to 40 percent of the stems in any one season. Stop harvesting after the end of June to allow enough time for the plant to recharge into the crown.

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) 231-8161,
Editor:Rich Mattern, (701) 231-6136,
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