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Ron Smith answers questions about plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I got a large schefflera about a year ago as a present. We have since moved and been in this house for four months. The schefflera has been in the same spot since we moved in. It gets indirect sunlight on the east side of the house. The plant actually is three schefflera plants braided together. One started to turn black. I cut it back an inch below the blackened part of the plant. It was doing fine, but it turned black again even quicker than before. The other schefflera plants connected to it are doing fine. I water it when the soil feels dry. (e-mail reference)

A: Cut the offending plant out. However, be very careful doing it so you don’t nick the stems of the adjoining plants.

Q: We planted our willow tree about six years ago as a sapling. It now is about 15 feet tall. I would like to cut it down to about 5 feet, but I am worried it might die. Would it survive? (e-mail reference)

A: If there are branches remaining where you make the cut and you will not be leaving any stubs (cut back to lateral branches), the tree should survive.

Q: I live in western North Carolina. When do you recommend trimming a river birch? I have several other trees that I trim in January and a sugar maple in April. Thank you for any advice you can offer. (e-mail reference)

A: In general, birches need very little pruning. If the tree is growing satisfactorily, then don't prune it. Remove only those limbs that are dead, diseased, damaged or interfering with the safe movement of vehicles and pedestrians around your property. If you prune in late winter or early spring before the tree releafs, then there will be excessive sap flow. While this does not harm the tree, it is a rich source of carbohydrates for insects and usually causes some owner concerns. The general suggestion is to prune the “bleeders” right after the leaves have fully expanded.

Q: I have some emerald green arborvitae trees that are turning brown. One tree has died. We do have a small dog that urinates underneath them. Also, last winter the snow pushed the tops down, so we shook the snow off, but the trees remained lopsided until I grabbed a piece of rope and tied it around them to give support. I don’t know if they went into shock after that. I hope I still have them next spring, so I hope you can shine some light on my question. (e-mail reference)

A: The dog urine could be contributing to the problem. If they were just planted, there is every likelihood that they were overwatered and/or planted too deeply. You may have to replace them next year. Plant the arborvitae at the right depth and keep your dog away from the trees as much as possible.

Q: About four years ago, I propagated five lilacs from two healthy and mature lilacs in my yard. They are all alive and blooming, but the one in the center is much smaller. Also, the leaves are a pale green and on the small side. This year, I noticed the leaves on the lilacs on either side of the center plant are starting to turn pale green and the leaves were not as full as last year. What could be causing this? I am afraid whatever is the cause is spreading. I have looked for insect and rodent damage, but have not seen any evidence. (e-mail reference)

A: You didn't tell me where you live, so I can't give you an accurate answer. If you live where the winters are mild, what you are describing sounds like a nematode problem. These microscopic animals resemble worms that feed on the roots of the host plant. In the right soil conditions, they can multiply unchecked and affect the nutrient uptake of the plant. It causes undersized and chlorotic foliage. Unfortunately, there is nothing a homeowner can do to eliminate the nematodes. You will have to call a licensed pesticide applicator because all nematicides are restricted use because of their potency. If you live where the soil freezes solid down a couple of feet, then the problem could be a root rot. The reduction in the volume of viable, healthy roots would result in the same symptoms. I suggest that you contact the plant diagnostic lab at the land-grant university in your state and send in some soil and leaf tissue samples for analysis.

Q: I have an ornamental orange tree. It appears to be healthy, and it flowers and produces fruit almost all year. At times, the tree sheds many leaves at a steady rate. The leaves that it sheds are not dead, but healthy, moist and green. What could be the reason for this? Some branches are bare and have been that way for some time. I have been doing some trimming. How much should I do and how often? This little tree has been in the same pot for 10 years. The pot is about 12 inches across and 10 inches tall. Is the pot too big or small? (e-mail reference)

A: Leave well enough alone. I'm afraid if you repot it at this stage, everything will come apart. Treat it mostly like a Bonsai tree. Spoon-feed it water and nutrients. You might want to harvest the fruit and pluck out the seed and plant some to perpetuate the plant. Leaf dropping is caused by cultural practices, such as alternating watering patterns, not enough light, temperature that is too cold, drafts from adjacent windows or the air being too dry. You've nursed it along for all these years to your satisfaction, so I would encourage you to continue, but be aware of some of the cultural conditions and practices I mentioned. Prune out any leafless branches, but prune lightly to keep it the dimensions you want.

Q: My cotoneaster hedges have dropped their leaves and gone dormant for the season. There are grass and weeds growing among the hedges. Can I spray these weeds and grasses with Roundup? Will Roundup kill the hedges? (Valley City, N.D.)

A: If you can be careful to not get into “revenge” spraying, the impact will be minimal because most weeds and grasses are dormant or very close to it. Try it with a material carefully applied to the leaf tissue. Spray just enough to wet the surface, but not run off the leaves. You probably will have to apply it again next spring before new growth begins. Again, be careful not to apply too much.

Q: I’ve had a Canadian red cherry tree on my boulevard for more than 30 years. I like the size, shape and color of this tree. However, the suckering is getting worse. Is there another tree that can be substituted that has the same size, shape, color and winter hardiness, but without the suckering? I also would like a tree that leaves no messy fruit, is fire blight-resistant and not prone to insect or disease damage. There is a tree several houses down the street that looks very much like the tree I have. It is larger in stature, but otherwise has the same appearance as mine. The big difference is that it doesn't sucker. (Bismarck, N.D.)

A: Get an artificial tree. Just kidding, but your question is a tough one to answer. The spring snow crabapple is fruitless and doesn't sucker. The prairie gem pear is fruitless (without a pollinator) and is majestic looking, especially with its white flowers in the early spring. Should any fruit appear, it is small and nonsignificant. When you are at the nursery, find out if any nonsuckering forms of the red cherry tree are available. Sometimes they are, but it would be a big disappointment if it would begin suckering after five to seven years. I suggest sticking with either one of the two I mentioned. Older, more stress-prone trees often are plagued with suckering. Minor wounds on the trunk and soil compaction also may trigger a suckering response.

Q: On your Web site, you recommend using 10-10-10 fertilizer on Christmas cacti. For the past several months, I've been adding 2-7-7 to my watering can and have gotten a lot of new growth. Two plants even have buds forming, which seems quite early. What could I expect if I use a 10-10-10 mix? As a point of information, I've found that it is better to overwater. I let them get too dry once, resulting in a lot of wilting and leaves dropping off. Usually, I water again a day or two after all the water that drained out the bottom has evaporated. Keeping a ceiling fan on in the room seems to help a bit as well. (e-mail reference)

A: Thanks for the excellent tips based on your direct experience! The 10-10-10 is a generic recommendation. Actually, yours is better because it has less nitrogen, but more phosphorus and potassium, which your flowering plant needs more than nitrogen. I never have seen it on our market locally. I certainly would not switch if you are having success with this formulation!

Q: A guy in my office took a couple of very small jade clippings and a couple of leaves and stuck them in the dirt just to see if anything would happen. The jades started growing, but they weren’t doing so hot because the plants were not near a window. I adopted them and moved them to my desk near a window. They grew very well. I added more clippings and even topped them at one point because they got too tall and thin to support the weight. All was going well until this past Friday. All of a sudden, my plants turned red. I haven’t moved the plants. The trunks have turned red and the leaves are red as well. There are some green leaves. I read that red edges are good because it means the plant is happy. What have I done wrong? Can I fix it? (e-mail reference)

A: Just when I think I have answered every possible question about jade plants, another one comes up! All I can tell you is that the red pigment (anthocyanin) is in reaction to some change in the environment, such as air, light, temperature or water. Carefully reflect on what may have taken place that is different and you likely will nail down the source of this change.

NDSU Agriculture Communication

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