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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I am looking for a recommendation on a ground cover that would be on a fairly steep south-facing slope. My goal is to get rid of the grass and replace it with something that spreads out and I don’t have to mow. A bonus would be something that has nice color in the fall and attracts bees and butterflies. (email reference)

A: One of the best ground covers is sweet woodruff. I’ve had this for several years and enjoy it for its low maintenance and effective cover. It does attract bees and butterflies but doesn’t have any decent fall color. It is completely hardy for this area. Another possibility is lily-of-the-valley. There are others as well, but few that can take a direct southern slope exposure during the winter months. Both will form a dense mat that is very resistant to weed invasion.

Q: I planted 10 arborvitae trees last fall. They are a techny variety. I watered them well after they were planted and we had quite a bit of snow during the winter. Because of that, I did not water them until August. The last week of September, we had more than 5 inches of rain in three days. Now the arborvitaes are showing some brown on the inside. I saw on your blog that this indicates they have been watered too much. Is it best not to water them again until spring? Also, I read on your blog that you recommend Miracle-Gro. I have not given them any fertilizer since they were planted. Should I give them some fertilizer before winter sets in? (Rockford, Ill.)

A: Overwatering could be a cause. However, it also is a natural reaction at this time of year, but it will vary depending on the preceding summer’s weather conditions. Hot and dry weather followed by a lot of rain will do what you describe. If you don’t get any more rain before it freezes, which should be at least another month in your part of the country, you should give them another shot of water before putting the garden hose away. Always allow the soil to dry somewhat before rewatering again.

Q: My question pertains to eight apple trees in our backyard. About three years ago, rust spots started showing up on the leaves. There were apples on the tree when this happened. Through the summer, the apples and leaves started dropping off. By the end of summer, the old leaves were off and new leaves started growing, but never any apples. This situation has been getting progressively worse through the years. This summer, we didn’t have any apples at all. Should we cut the trees down and start again or is there any hope? About 100 feet back is a row of cedar trees that were planted long before the apple trees. We’ve had the apple trees for about 15 years, so we don't think the problem is cedar apple rust. Are we wrong thinking that? (email reference)

A: Yellow spots showing up on the leaves and fruit, followed by leaf and fruit drop, sounds like cedar apple rust. Check your cedars this winter for the fruiting bodies. Remove and destroy the fruits as they are found. If your trees don’t leaf out next spring and bear apples, then get back to me because something else is at work here that is not obvious.

Q: My mom had what we called a purple leaf plum tree. I’m attaching pictures from two years ago when the poor thing was so loaded with fruit that it had to have help. This year, the tree was loaded with fruit (more than 60 pints of jam and jelly), but then it died. We have no idea what happened. The tree lost all of its leaves and the branches died. By July, it had to be cut down. I thought it might come back, but my parents didn’t think it would. Mom is trying to find another one. However, every nursery we talked to said that purple leaf plum trees don’t bear fruit, so she was wrong about what type of tree it was. One local nursery has promised her a thundercloud plum tree when a shipment arrives. However, after reading your discussion board, I wonder if a thundercloud is the right tree for her. Mom likes the purple leaves, but the fruit is the important thing. I have to wonder if the F-5 tornado that came through our area in April, the bumper crop and the fact that this was our year for cicadas had something to do with the tree dying. In any case, could you give me some information on the best plum tree for her? We live in northwestern Alabama. (email reference)

A: Your best bet is to contact the Alabama Extension Service office in your county. Someone there should be able to assist you better than I can. Those were beautiful plums on that tree. I bet the plums tasted good right off the tree, as did the preserves that were made.

Q: Is using milky spore to control grubs effective or a waste of time? (email reference)

A: It is effective. What the product doesn’t do is kill them outright. It takes time, temperature and population to work. The more grubs in the soil when you apply it, the better, because infected grubs breed more of the disease. The best time to infect large numbers is early fall because the grubs are in warm soil and chewing grass roots to put on fat for the winter. Applying a concentrated form of the disease (available in bags and shaker cans at most garden centers) anytime during the summer would be best. Just don’t use any other grub killers because the milky disease spores wouldn’t have anything to infect. Grub insecticides act quickly, while milky spore disease acts slowly. If homeowners don’t want to wait that long, then they should do a lawn insecticide application for grub control by following label directions.

Q: I had a jade with one main branch and one shoot coming off it. There also were two smaller stems. My dog got a hold of the plant and now the two smaller stems are gone. The main branch and shoot were chewed on. I had to take off the shoot branch because it became too weak and was separating. I read on other forums that I should cut back the stems, let the fresh cut close up and then replant. The main stem and the shoot I cut back both have started to shrivel and are hollow. I replanted some of the leaves that fell off, but they died. I have not taken the main stem out to check the roots because I don't want to cause any more stress than necessary. I am wondering what I need to do from here because I am about to throw away the plant if I don't see any recovery possibilities. Any answers or advice would be greatly appreciated. (Florida)

A: Bad dog for chewing on your jade! Placing dropped leaves into the soil will not work. The leaves dropped for a reason, so they are not good propagation material. If you want to go that route, remove some of the leaves still attached and use them as propagules. Before giving up and dumping the plant, I would suggest cutting it back to about a 6-inch stub. Continue watering the plant as you have been. Give it six to eight weeks to see if any buds break on the stem or from the crown. If not, or the stub rots, then dump it.

Q: I have a white flowering lilac bush that we believe is 30-plus years old. When I came home today, I noticed it was blooming again. It's mid-October. In all my years, I never have seen or heard of a lilac bush blooming again. Is this common or rare? (email reference)

A: It is not common, but it does happen with flowering shrubs. Hormonal imbalance or stimulation can cause this irrational blooming to take place. The plant will straighten itself out eventually and get back to the normal blooming cycle. Odd weather conditions, such as too much rain or too cold or hot, can throw the plant’s sequence out of whack. Physical injury is another possibility.

Q: When harvesting my apples and cutting them open, I found the interior flesh was discolored and had dark streaking. What could have caused this problem? (email reference)

A: Apples are wonderful fruits to grow and eat, but we have to understand that the apples also are highly desired by at least a couple of pests. Two major pests are apple maggots and codling moths. I can give you the basics of preventive care. Pick up all fallen apples and anything left on the tree after harvesting is over. Also, rake up all the leaves. This spring, do some intelligent pruning to open the crown. This will allow for better air and sunlight penetration. Spray the tree with dormant oil before new growth shows. This will kill off any overwintering codling moth larvae under loose bark. Spray the trees at flower petal drop with an insecticide. A spinosad-containing product, such as Monterey Garden Insecticide, is a fast-acting, natural product that kills a wide range of troublesome insects. If unavailable, some alternatives are pheromone or sticky apple traps. Pheromone traps get the males thinking that they will mate with the females, but they will be permanently disappointed. Sticky apple traps are red globes that are covered with a sticky substance that attracts the female. She ends up getting stuck and dies. Finally, conventional insecticides, such as Sevin, are applied starting at blossom drop and continue through the growing season. Hope this helps.

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 – Nov. 2, 2011

Source:Ron Smith, (701) 231-7971,
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.ed
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