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Hortiscope

Ron Smith answers questions about the world of plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have a clump of four white birch trees that look very healthy. However, winter ice storms have caused the trees to look bad. They look great up to about 20 feet, then they start to droop in every direction. I would like to cut off the tops of each tree. This would prevent the ice from damaging the trees each year and improve the look. Would this harm the trees? (e-mail reference)

A: I don't recommend the wholesale pruning of birch trees! I would encourage you to contact an International Society of Arboriculture certified arborist to have the tree inspected to see if anything needs to be pruned and to have it done properly. I've seen too many healthy birch trees ruined by well-intentioned homeowners doing what they think is the right thing. For the longevity of your birch trees and your happiness, get someone in who is qualified and comes with good recommendations.

Q: For years, I have planted marigolds as a border around the perimeter of my garden. Until this year, the marigolds have been a huge success. My problem now is an influx of Japanese beetles. They sit on the flowers or burrow into them and chew away. I have been picking them off and dumping them in soapy water. However, it takes a lot of time and must be done every day, even twice a day at times. Is there a better strategy? (e-mail reference)

A: Get a lawn care company to apply a soil insecticide to kill off the beetle grubs that are infesting your soil, feeding on grass and other plant roots. This will take care of them at the source. Most treatments are effective for up to three years. Spraying the beetles with an insecticide, such as Sevin or Malathion, will do the trick at that point, but more will be coming from the soil next year, so don't overlook that treatment.

Q: My mother-in-law gave me a small jade plant about a month or two ago. It was doing great on a side table in our living room. The only damage that it sustained was one kitty bite. The first day we got the plant, the cat started digging in the dirt a little around the stalks. However, I noticed that five to 10 leaves were falling off every day. I thought it was the cat playing with it, so I moved it to our mantel, but the leaves kept falling off. I moved it outside, but the leaves still keep falling off. In addition, a few of the stalks turned brown and withered, so I pulled them out of the pot. It has grown some new leaves, but I am afraid that it will be completely bare soon. I am very worried because I want my plant to live a healthy life. Should I stop moving it around or should I keep it outside and let it adjust to the porch? (Houston, Texas)

A: Jade plants don't respond well to being moved, so let it stay where it is. It will acclimate to that location. You might be overwatering the plant. Allow the soil to dry completely before watering again. This is a succulent and does not require as much water as other houseplants might. Keep in mind that this is a tropical plant that comes from a hot and humid climate, so it is genetically programmed to handle any type of weather that Houston can throw at it.

Q: Due to safety and property issues, we had three large cottonwoods removed from our yard. We are replacing them with maples. One nursery told us we could plant the new maples in the same holes left by the cottonwoods. However, the tree removal service said it hasn’t had much success with new trees being planted in the same holes. Since we’ve spent quite a bit of money on new trees, we don’t want to risk losing them. Any advice would be appreciated. (e-mail reference)

A: It is always better not to plant in the same hole in which another tree has been growing. There may be some undetectable root fungus in the holes that could do the new plants some harm. I suggest locating them some distance from the original stump holes if possible.

Q: I planted two Easter lily plants in front of my south-facing house. That was last April. Now they are blooming. Will they come back in the spring? Should I cover them with mulch this fall and hope for the best? Any ideas would be helpful. (Fargo, N.D.)

A: Unless you live inside the Arctic Circle, you don’t need to do anything to protect these plants through the winter unless it makes you feel better to do so. These are tough plants. We still have Easter lilies growing in our garden from many years ago, but make no effort to protect them.

Q: I have a weeping fig tree that has been in the family for many years. Not long ago, I had noticed that the tree was losing many leaves. The tree has little, stringy pieces that are growing along the branches and eventually killing them. I'm not sure if it's a fungus or an insect. I've treated the tree with a fungicide and an insecticide spray, but have not seen any results. (e-mail reference)

A: What you are describing sounds like aerial roots, which are common on plants that grow in humid, tropical climates. I don't know what else to tell you because you have tried insecticides and fungicides. You didn't say where you are living, but I would suggest that you make contact with your local Extension Service office to see if there is someone who can assist you.

Q: I have a 3-year-old spider plant that I hang outside on overcast days so the plant can feel the wind. I noticed some black to greenish pieces on it. Upon further inspection, I found some small, green, worm-looking things on it. They also bite! My poor plant is being eaten alive. I have tried all my normal, natural remedies, but these little buggers just keep on munching! What can I do? (e-mail reference)

A: This is an instance where you have to give up on the natural stuff. Get a houseplant insecticide that is systemic in action. It is absorbed throughout the vascular system of the plant. After these biters take a taste, it will be their last.

Q: I have a dwarf maple tree that has tiny, white bugs on it. They are 2 to 3 millimeters in length. The bugs attach themselves to the top limbs and kill them. They are not in the bark of the tree. The leaves have started to fall off. What are they and how can I get rid of them? (e-mail reference)

A: If you could send me some photos of the insects, I could give you a more accurate answer. They might be mealy bugs, which can be controlled by using a systemic, such as Bayer Advanced Tree and Shrub Insecticide. If you can, try to find out what the insect is by exploring the Internet.

Q: We purchased and planted late spring a few miniature common junipers. They are planted on the south side of our home in a rock garden. They receive full sunlight. When spreading the branches a little, we see lots of brown coloring inside the tree. I thought it would all be green like the outside of the trees. I have been giving each tree a gallon of water a day, except when we have received ample rain. Am I giving them too much water and too often? There is no information on the tag that told me how to care for the trees. I have not been able to find anything on any Web sites pertaining to this particular juniper. Also, I need to know how to prepare the trees for winter. (Ashley, N.D.)

A: This is probably the same thing as the compressa juniper. I’ve never heard of the cultivar you mentioned. The discolored needles on the interior are normal. From your description, it sounds as if you might be overwatering a bit unless you have sandy soil. A gallon of water a day is a lot for these small plants. There is no way they could need that much water. They should be allowed to dry out between waterings. A winter southern exposure is murder on plants like this. I would suggest wrapping the plants in burlap just as winter arrives to keep them from being scorched by the sun while the soil is frozen.

Q: We planted many poplar trees in our yard 10 years ago. They have started to become a real nuisance. The leaves dry and fall off prematurely. The roots are above ground and have become quite invasive. We have cut several of the more manageable ones down, but the stumps continue to be very prolific in their branch and leaf production. Sprouts from the underground roots are coming up all over the yard. Can you give us some advice on what to do to get rid of these shoots and to kill the stumps so they no longer produce? (Devils Lake, N.D.)

A: Treat the sucker growth or sprouts as weeds. Treat them with something, such as Weed-B-Gon or Trimec. This eventually will kill the entire root system. Now would be a very good time to do this.

Q: I had three large willows in my backyard. They had a very bad case of root gall, with large, bumpy nodules around the base and on the roots. They were rotting from the roots up. One fell down last year, so we cut the other two down this year because we were worried about the same thing happening. We had the stumps ground up and removed what we could. There still are lots of rotten roots and nodules underground. The three trees spanned most of my backyard. Can we plant more trees, shrubs or flowers in the soil? Do we have to watch what types of things we plant? (e-mail reference)

A: I would say that you probably could plant in the backyard, but not over the old stump locations. Willows have their own collection of pathogens that are host specific in most cases. Just about any other woody plant species has more resistance to these pathogens that are typical to willows. I would go ahead and plant, but remove any old root residue from the planting site during the process.

Q: I have mules that love to eat everything. I need to know if crepe myrtles are poisonous to equines. (e-mail reference)

A: All I can tell you is that crepe myrtle is not listed in my poisonous plants references.

Q: I just ran across your Web site while researching Christmas cactus. I have two plants. One has a bright, fuchsia flower. The other plant has a soft, white bloom. Both bloom vigorously (I have never given them periods of darkness or altered their watering or feeding schedules). They don't bloom at the same time. However, I did have a flower from each open at the same time the last time they bloomed. I brushed the flower from the white one deep into the fuchsia flower, just for the heck of it. Shortly after that, the petals of the flower dried up, but the base became firm and closed up. It has been that way for several months. I am wondering if there might be seeds in it. It looks like it might be a seedpod. I have been watching it daily because I don’t want to lose the seeds. (e-mail reference)

A: Harvest the pod and spread whatever is inside on white paper or a clean tabletop. Plant the seeds in a milled sphagnum media and keep it moist. If the seeds are viable, they should germinate in a few weeks.


NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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