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Hortiscope

Ron Smith answers readers' questions about the world of plants and gardening.

By Ronald C. Smith, Horticulturist
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NDSU Extension Service
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Q: We need to move a large, beautiful lilac bush. When is the best time to relocate the bush? What's the best method? (e-mail reference)

A: The best time is early spring while the bush is dormant. The next best time is in the fall after the leaves have dropped. The worst time is now. If the shrub is accessible, a small-scale tree spade probably would do the best job because it would be able to encompass the largest mass of roots for moving. Otherwise, it would be too big to be moved by hand because too much of the root system would have to be left behind.


Q: My young maple tree is losing leaves (many) and I just noticed that the branches seem to be turning black. I am not sure what variety it is, but the leaves are green. They seem to be healthy leaves (not brown) when they fall off. I would like to save it because I planted it in memory of my son, who passed away. Until this spring, it has grown very well and has been healthy. (e-mail reference)

A: This could be what is known as sooty mold, a secondary pathogen that results from aphid- feeding activity. Carefully examine for aphids on the underside of the leaves and the small, new growth. Aphids excrete a sticky substance known as honeydew that causes this mold to grow under the right conditions. Control the aphids and the mold should disappear. If not, then a fungicide application will clear it up.


Q: We purchased a 30-year-old home two years ago. There is a wonderful weeping birch that I assume was planted shortly after the house was built. I have noticed that there are a lot of dead branches. What can I do to ensure that we have this majestic tree with us for many years to come? (e-mail reference)

A: Get in touch with an International Society of Arboriculture-certified arborist to trim the dead branches. The tree is probably under attack by bronze birch borers, which if allowed to go unchecked, will kill the tree at some point. The tree also should receive an injection of a potent insecticide that will translocate through the transpiration stream and kill actively feeding larvae. Additionally, the tree should be fertilized almost every year and kept watered to increase its vigor. This will make the tree less attractive to the borer.


Q: I am having problems with my vegetable garden. The peas came up nicely, but it didn’t take long for the leaves to start curling. I dug some up and found rotten roots that were brownish and soft. What would cause that? I also am having problems with my cucumbers. They also came up nicely, but then the leaves started curling. They haven’t died, but aren’t growing. These plants also have rotting roots. We are very dry here, but I try to water once a week. The only thing I have done differently is that last fall I put a load of manure on that spot in the garden. This spring, I took most of it to other gardens, so there wasn’t much left when I tilled it. There are self-seeding flowers coming up in the same spots as the cucumbers and peas, but the flowers look fine. Any ideas what could be wrong? (e-mail reference)

A: The manure brought too much salt to the soil. The salt is killing the seedlings and transplants. The flowers that are volunteering are tolerant to high salt levels. With copious watering, the salts should decrease during this growing season. You successfully should be able to plant a garden next spring.


Q: I have a 27-year-old linden tree that is sick. The leaves are pale green and small. It appears to have some black substance on the bark. It was like this last year, but not as bad. Can it be saved? Thanks! (Oakes, N.D.)

A: The tree has an aphid or cottony cushion scale problem. Carefully check the leaves or get an ISA-certified arborist to check the tree and make recommendations. Only an on-site visit or possibly a sample sent to our Plant Diagnostic Lab in Waldron Hall on the NDSU campus in Fargo could give you a positive determination. Address the sample to Kasia Kinzer at the above location. The zip code is 58105. Send it dry in a plastic bag at the beginning of the week. That way it won’t sit in the post office during the weekend.


Q: I bought a large bag of Miracle-Gro potting soil. I used about one-fourth of it and then stored the rest in a watertight container. I went to get it to add to some soil for tomato plants, but the Miracle-Gro was full of black ants. Will it hurt the tomato plants? (e-mail reference)

A: I never have known ants to hurt tomato plants, so I would go ahead and use it. The ants will settle into the surrounding environment or be preyed upon by the local population, so you should have nothing to worry about.


Q: We have an old apple tree that we built a deck around. There is sawdust all over the deck on a daily basis. Yellow leaves are dropping and the main trunk and branches have bark that is curling and peeling off. We haven't done much to the tree in the eight years we’ve lived here. We love the tree and will do anything to save it. (e-mail reference)

A: It sounds like borer or bark beetle activity that is slowly killing the tree. It should be evident where the sawdust is coming from. Once they invade the tree, they are very difficult to control. If the borer or bark beetle activity can be located and the branches that are infested removed, that is the best immediate control. After that, spray the rest of the tree with an insecticide known as Lindane. It is toxic to borers who try to reinfest the tree and has long residual activity. If you do spray, do not eat the apples from the tree this year.


Q: I inherited a grapevine that I assumed was wild, but who knows. In the spring, I get tiny grape clusters, but they disappear in a few weeks. It's like they burst into flower and then they're done. Is there anything I can do to get fruit? (e-mail reference)

A: You may be seeing the flower buds, but not the fruit. If the flowers were not fertilized, they will not produce fruit. You may have one of those all-male vines that do not produce female flowers or vice versa. Most grapevines are hermaphroditic, which means both sex organs are present ("perfect flower"). The vines are wind-pollinated, so with no other vine in the area, you won’t get fruit set.


Q: We have a producer who has slime mold in his grass. He wants to know if he can spray it with anything. (e-mail reference)

A: Anything that can be sprayed to control the problem would impact the grass as well. The best bet is to core aerate, follow up with a power raking and try not to water a lot. Also, tell the producer to cut in half whatever he/she is doing.


Q: We have large, white patches in our lawn. The problem seems to be where there is shade for part of the day. Is this a disease or fungus that has to be taken care of or do we just let it go and call it weather-related. Any help you could give would be greatly appreciated. I also have had cucumber and bean plants die. The plants dry up and look like they rot off or were chewed off, but it is hard to tell. I put Sevin on them, but I don't know if that will help. Thank you. (Oakes, N.D.)

A: It is probably powdery mildew arriving early because of the high humidity and dew points in your area. The grass should outgrow it with a little encouragement from a light application of fertilizer and collecting the grass clippings when mowing. It is not lethal to the grass plants. As for the vegetables, it could be any number of diseases because it is hitting different crops. Sevin is an insecticide, so it will not control the problem. Try to find a fungicide appropriate for vegetables, such as Funginex, which should be available at just about any garden store.


Q: We have a terrible problem with blossom end rot, but only on our zucchini. The tomatoes and cucumbers are fine. Any ideas? (e-mail reference)

A: Harvest the zucchini, cut off the degraded end and consume the rest. Avoid vigorous cultivation and wide swings in irrigation cycles. As with some tomato cultivars, blossom end rot usually is limited to the first fruit set. Later fruits are usually free of the disease.


Q: My gloxinia bulbs (purchased a few months ago) were planted in pots that seemed too deep for the bulbs. After growing a few small leaves, the stalks suddenly fell, went brown and wilted. I assumed it was a fungus, so I dug the bulbs out and saw that all the roots were rotten. I cut the bulbs to see if I could save any part of the bulbs. To my surprise, the inner color of the bulb was dark brown. Is this the right color? Also, how can I tell if my other gloxinias are having root rot or are starting to go into a rest period? I may have overwatered them. Thank you very much for your valuable help! (e-mail reference)

A: Having never cut a gloxinia tuber in half, I honestly cannot say if this is the color they are supposed to be. My guess would be no because the roots had rotted. As to the rest period versus root rot, if you have the tuber in the right soil mix and pot, keeping the media just moist during the flowering period should not lead to root rot. Once past the flowering period, allow the plant to "die down" by withholding water as would happen in the plant’s natural setting in the tropics. This should last about six or more weeks. Then slightly moisten the media and continue to do so until new growth is observed.


Q: I live in central South Dakota. We are in a very dry area and are seeing a lot of spider mites on our spruce and cedar trees. What can we do before there is some damage to our trees? Some are large, older trees and some are newly planted. I know that a good rain would do the trick, but don’t think it will happen in the near future. Is there a chemical that I can use, such as malathion? (e-mail reference)

A: If you can, hit the trees with a hard spray of water from a garden hose or a pressure sprayer. If you have a family member who belongs to the volunteer fire department, get the tank truck and use that to blast the mites. I used to be a volunteer fireman and used the tanker for such purposes. Of course, that assumes there was no fire that needed putting out! Orthene is an insecticide that will provide some mite control, but entomologists tell me that using any chemicals to control them results in a resistance buildup that takes place quite quickly. With water, that doesn't happen.


Q: I purchased variegated ivies that had a nice blue-green hue to them, but after they started to grow at home, they turned a regular green. Is there anything I can do to keep it the bluish-green hue? One more variegated question: I have an old hosta given to me by my grandmother some 30 years ago. In the spring, it comes up green with a variegated leaf, but then the variegated leaf turns green. Is there anything I can do to keep the variegation? (e-mail reference)

A: Variegated plants can be fertilized in the same fashion as other plants of the same species. You might ask the nursery what its trick is to produce the blue-green hue that you like. As to the hosta turning from a variegated to a full green, I have no idea other than it is the characteristic of this particular cultivar, so you have no choice but to accept it.


Q: I enjoy reading the good information you provide concerning trees. One method I've found to control web worms is to attach a propane torch to a long pole and burn the nests. I used to have them all over my cottonwood trees, but got rid of them after burning the webs for a couple of years. Someone told me that this disrupts the worm’s cycle. The drawback is dodging the flaming webs as they fall to the ground. Dodging the webs can be hazardous if standing on a stepladder and holding a 20-foot pole with a propane torch taped to the end of it. I know this sounds like something out of a Patrick McManus book, but it sure worked for me. (Bismarck, N.D.)

A: Yes, I have done that, too, but never on a ladder or with a propane burner attached to a long pole. You are a brave man. Your solution definitely will interrupt the worm’s life cycle. Don't try this when you get over 60! Thanks for the nice comments about the column!

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NDSU Agriculture Communication

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

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