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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: We are having root problems caused by a poplar tree. The roots are destroying the garage foundation. My husband is attempting to dig to the roots to destroy them. How deep do the roots grow and how much do they spread? The tree is 50-plus years old. (e-mail reference)

A: This is like asking me how deep the water is in a lake! Poplar roots go deep and wide, but that depends on various factors, such as soil type, water table or climate. The deep roots are not the problem. It is the surface roots that are competing for air, water and nutrients that are a problem. If he can get the roots that are down a couple of feet or so, that would be adequate. You might want to consider the value of keeping the tree or replacing it with another species. A poplar that old is bound to have some hazard problems. You should have it checked out by an International Society of Arboriculture certified arborist.

Q: A good friend of mine took some cuttings from her plant, rooted them and gave them to me. She said it was from a begonia plant that belonged to her late grandmother. The plant does not produce flowers, but I’m not sure if it is supposed to. The plant has large leaves that are red underneath and green on top. It looks like only half a leaf. If this is a begonia, what type is it? Also, tiny flying insects have made their home in the soil and around my house! They have chewed on the leaves and have caused many of the leaves to die. They became so bad that I had to bring this beautiful plant outside. It died two days later. I still have some of the insects flying around the house. My friend could give me another plant, but I am very reluctant because of the insects. Just so you know, I have 14 other plants in my home, but these insects did not bother with them at all. What do you think? (e-mail reference)

A: It could be a Rex begonia, but that is just a guess from what you told me. As to the insects, I have no idea what they are! When planting, always start with clean plant material and use a sterile or pasteurized media. If the insects should show up again, get after them right away with an insecticidal soap or some other low-toxicity insecticide.

Q: I bought a jade plant at a fruit stand. It is in a hanging basket and has long legs hanging down. I am wondering if this is normal. I don’t think it got enough light based on reading some of your answers to questions about jade plants. I also think I need to prune it, but there are no lateral stalks or a trunk to this plant. Should I waste my time with this thing? I think it looks nice the way it is right now, but I don’t want unhealthy plants mixed in with my healthy plants. Thanks. (e-mail reference)

A: Those are aerial roots you are seeing, which are not a problem. Apparently, the plant was kept in a very hospitable environment to develop these roots. It is not a sign of poor health at all, so keep it!

Q: I happened to stumble across your Web site while looking for information on a tree problem we are having. We have a big tree just off our back patio. I'm not sure what kind of tree it is, but I did attach some pictures. It was beautiful, but many of the branches seem dead and it has seemed to retain its seeds for a very long time this year. For the first time all year, we are seeing some nice leaves sprout, but it is September. We did have a new patio put in last year that goes very near its base, but no closer than the old patio. I am wondering if that could have any impact or if we are seeing the end of this tree. Is there anything we can do to help it? Any help or advice you could offer would be greatly appreciated. (e-mail reference)

A: It is a green ash, but it is in decline. This is a result of unintended construction damage that happened when the new patio was built. The major damage was done by soil compaction around the roots, which reduces the air in the soil that is necessary for survival. The tree still might be able to be saved. Contact an International Society of Arboriculture certified arborist who is good at diagnosing problems, not just good at removing trees. Perhaps with soil aeration and some fertilization, the situation can be turned around. However, once the tree starts showing this kind of stress symptoms, it may be difficult to save it. Make sure that someone doesn't take your money for a treatment that won’t do any good, so be sure to check the arborist’s credentials and license.

Q: I have a rhubarb patch that I have done nothing with the last eight years. I dug it up, mixed together top soil and mostly cow manure and put the plant back in the same spot. Reading some of the information on rhubarb, I now realize I probably should have split it up, but it has not spread at all during the eight years. It has produced many more stalks this year, but they are dry and somewhat hollow. Is the plant too old? (Bancroft, Ontario)

A: It probably would have benefited from being divided. As for the hollow stems, they are naturally somewhat hollow, but anything in excess would indicate a problem with being too dry or too old. Rhubarb plantings are a lot like peonies. If planted the right way and in the right location, they often outlive the gardener.

Q: I have a question about my apple tree. The tree had a heavy fruit set this year, but the fruit has been falling off the tree the last three to four weeks. Approximately three-fourths of the apples have fallen from the tree. Do you have any idea why? The tree was hit by hail in early July, but the apples that are falling do not appear damaged. I’d appreciate any information you can offer. (Fargo, N.D.)

A: I'm sorry, but I don't know why your tree would be dropping so many apples at this time of year. Generally, apple trees drop fruit early in the season if an excess set takes place. This often is called June fruit drop. Something is causing an abscission layer to form at the apple stems, which is causing them to fall off the tree. This could be due to a nutrient imbalance of some kind or a shift in the weather that is causing this problem. If the tree is healthy and vigorous, I don't think you have anything to worry about except to keep up with the apple drop.

Q: What kind of fertilizer can I use on Colorado blue spruce trees? I just planted them this spring. Can I fertilize now? (Manchester, S.D.)

A: Save your money. They do not need fertilization at this time. If you really think they should be fertilized, do so next spring as new growth is starting.

Q: I have a well-established apple tree that sits in the middle of a small flower garden. My husband did some landscaping around the tree this summer. This fall, we plan to dig up the flowers and haul in a foot of dirt because I want a raised flowerbed. How will this affect the apple tree? (Redfield, S.D.) A: A foot of soil over the root system definitely will affect the health and stability of the tree. That much dirt very likely will end up killing the tree. If you must backfill over the roots, use a sandy loam and add no more than is necessary. Also, do not put the backfill soil right up to the tree's trunk. Leave 6 inches clear around the trunk.

Q: I am going to plant a honey crisp apple tree next spring. I understand that apple trees need a pollinator. We have two flowering crabs that would be within 50 to 60 feet and a large one about 100 feet away. Also, the neighbors across the street to the east have several apple trees in their backyard and a home across the street to the south has two. Would this be enough to do the pollination or should we plant another pollinator? What would be a good choice? (Wadena, Minn.)

A: Your honey crisp will have plenty of pollen available for proper fruit set, so you have nothing to worry about.

Q: I purchased two variegated red twig dogwoods from a national chain. They were wilted and the roots were extremely dry. These were “end of season” trees, so no one was taking much notice on their care! Once I got them home, I saturated the trees with water and set them on the north side of a building to give them a reprieve from being abused. They had somewhat recovered a week later. Some of those leaves that had been shriveled do not appear to be healthy enough to come back, while others might make it. Should I try to plant them in their appropriate places this fall or should I put them into a garden spot for the winter? I don't want to add any more stress than is needed. (Audubon, Minn.)

A: Get them planted as soon as you can. Fall is an excellent time to do tree, shrub and herbaceous perennial plantings. If there is a spark of life left in these plants, get them to the site you want. One planting is always better than doing it twice.

Q: I purchased property that has two lovely, very old Italian plum trees. We had a great harvest the first year, so I brought in some experts to do some pruning for the following year. Some tarlike substance also was spread on a small slit in one trunk. Last year, I had another bountiful harvest of delicious plums. This year, one of the tree's major limbs has turned black. There are healthy suckers growing and the rest of the tree is loaded with plums. Should I have this limb removed? My cats love to bask on this particular limb. I live 40 miles south of Missoula, Mont., in the spectacular Bitterroot Valley. (e-mail reference)

A: Such a tough moral choice to make! You can cut off a branch your cats like to sleep under or keep it so it can spread whatever it is that killed it! My take on this (from one who has owned cats most of his life) is that cats are creative creatures. If the cats are deprived of something, they will find something else to keep them happy. I'd suggest calling the experts back in and getting the limb taken off and do any other corrective pruning these trees may need.

Q: I have nine roses planted in black dirt on the southwest corner of the house. They are protected by the garage on the west, a wall on the south and the house on the north. However, a lot of snow piles on that spot. What is the best way to winterize these roses? I usually pile leaves on other plants and cover them with a pail. Will this work for the roses? Also, my onions were in new barn dirt and did excellently, except that some of them were soft as marshmallows. What got to them? (Valley City, N.D.)

A: Your procedure should work for the roses. Cut them back after a hard, killing frost, then as the ground is about to freeze or become snow covered, get them covered for the winter. Rot got a start in your onions. Unless it is well composted, it isn't a good idea to plant onions in heavily manured soil.

Q: I have a large arborvitae that was been healthy for years. However, during a six-week period, it turned completely brown. At the base of the tree there is brown, goopy, mold spore stuff growing. Any ideas? (e-mail reference)

A: From your description, I doubt that this mold is the cause of the problem. This usually is a saprophytic fungus that is working on digesting the dead organic matter at the base of your plant. This may or may not be good news because the dead organic matter may be the base of your tree! More than likely, it is working on the mulch you have around the tree.

NDSU Agriculture Communication

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