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Hortiscope

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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have a sod lawn that was installed in 2005. It appears to be blue grass and I believe it has peat as a base. I’ve had a lot of trouble with the grass since it was planted. I have poured hundreds of dollars worth of water on it. It is the last yard to green up in the spring and first to turn brown in the fall. I have the grass aerated each fall. This spring, I had the grass dethatched and overseeded with a fescue blend. I took 40 bags of thatch to the curb two weeks ago. It may be too early to tell, but I'm concerned that it is not greening up as much as I hoped. Any suggestions? I’m considering having it replaced if I don't see results this year. (Moorhead, Minn.)

A: If you overseeded with good-quality grass seed and are a little more patient (six to eight weeks), it should start rewarding you with the hardy green grass you are looking for. It probably will give you little comfort, but you are not the only one to have problems with peat sod. It can be used in our heavy Red River Valley clay soils, but the preparation and follow-up leaves something to be desired. It is strongly suggested that the soil be core aerated prior to laying the sod and the cores removed. After the sod is laid, at least annual core aeration is encouraged for the following three years to get the roots to penetrate and the water to move beyond the clay surface. If this is not followed, a "perched water table" is created between the sod's peat base and the finely textured, hard clay surface. This sets the stage for poor rooting and disease problems to take place. You at least have a good environment for seeding and getting the grass to grow in that sod base.

Q: I planted strawberries three years ago. I'm not sure it was a good idea, but I allowed the spring crop to mature. Would fertilizing now to help the summer and fall crop be a good idea? Thank you! (Wilmington, Del.)

A: Fertilizing after the fruit is borne is always a good idea. However, don't overdo the nitrogen. In other words, don't throw any leftover turf fertilizer on the strawberries. A 5-10-10 or 5-10-5 will do a nice job of reinvigorating the strawberry plants.

Q: We have two silver maples in our backyard that were healthy and growing for the six years we have lived in our home. They are huge, tall trees. This year, I noticed that a portion of one of the trees didn’t leaf up as fast as the rest of the tree. The limb did fill in eventually. We called a tree specialist to look at the trees. He told us the trees had spider mites that would kill the trees. In order to save the trees, he told us we would have to inject pesticide into the roots and allow the tree to draw it up and kill the mites. The process will cost $1,000, which would be hard for us to come up with. We love the trees, so I don’t want to see them die. Is there any hope? Please help! (e-mail reference)

A: I'm all for the entrepreneur in our society making some money, but that sounds a little steep to me. I also question the diagnosis, unless we are talking about you living in a hot, dry climate. Spider mites are active during the weather conditions I just described. Spider mites are rare, if not totally absent, during the cool, damp and rainy seasons of spring and fall. The fact that the branch did leaf out would lead me to believe that it is struggling with a canker or vascular disease of some kind. If that is the case, having the trees professionally fertilized would be an approach to consider, but it depends on the extent of damage. This would stimulate growth and compartmentalize the disease areas. Such a treatment would cost far less than the injection of a miticide.

Q: I have a couple of young basswoods in my yard that I inadvertently damaged with a broadleaf herbicide (2-4 D Ester) trying to control creeping Charlie. Is there anything I can do for the trees? How long does the 2-4 D last in the soil? The basswoods seem really sensitive. A nearby crab apple tree was unfazed. The tops of the basswoods seem to be the most affected by showing the most leaf curl. I don't believe drift is the problem. Does rain or lawn watering carry the herbicide to the roots? Is there a short-lived broadleaf herbicide that would kill the creeping Charlie and then break down quickly? My creeping Charlie problem is bad. A nearby patch of woods has a solid blanket of the stuff. Any thoughts on how to keep it out of the lawn without killing my trees? I really enjoy reading your Hortiscope pages! (e-mail reference)

A: A linden tree the age you describe should have no trouble recovering from the herbicide drift that probably occurred during a rain event. With the heavy infestation of creeping Charlie that you describe, you are a perfect candidate to use Twenty Mule Team Borax. Dissolve 10 ounces of Borax in 4 ounces of warm water. Add the mixture to 2 1/2 gallons of water. This is enough to treat 1,000 square feet. My colleague, Harlene Hatterman-Valenti, was a pioneer in the use of this material when she was working on her degree at Iowa Stage University. Be aware that boron is an element used by plants for growth, but in microdoses. What the plant is getting is a macrodose that will be toxic to it. If you live in a part of the country that is high in boron, applying this strong dose may make it inhospitable for your lawn grass. The alternative is to accept this weed as your lawn to save on the frustration of attempting to get rid of it.

Q: I have a snowball vibrunum bush. For the past two years, the leaves have started turning black and curling up. Some of the flower buds did the same thing. I noticed ants all over it, so I sprayed it with an insect spray and sprinkled ant powder around the bottom. The ants seem to be gone now. Is the problem happening because of the ants or is there some other disease that could be causing it? (Gackle, N.D.)

A: The ants are going after the aphids that are attracted to this shrub. Spraying to control the aphids also will eliminate the ants. The ants milk the aphids of their honeydew and use it as a source of food.

Q: I like planting trailing and regular petunias in pots. I always put the pots in the sun, but sometimes they look a little straggly. I like the more rounded, compact look. Is there a special technique to pinching them? I try to deadhead the nontrailing plants, which helps a little. (e-mail reference)

A: Go ahead and prune the stragglers back somewhat to get them to bush out. Don't be afraid to use a water-soluble fertilizer, such as Miracle-Gro, about every other week to keep the plants flourishing. Petunias are heavy feeders, but the reward is their beauty for doing so.

Q: The mankana ash tree on my boulevard is toast. Any recommendations for a replacement tree? I don't want anything that drops seeds or pods, suckers and definitely don’t want to plant another ash tree. When I look around town, some of the nicest trees are elms and linden big leaf trees. Thanks as always for your expert advice. (Fargo, N.D.)

A: Lindens are great trees to have. I have a Redmond linden in my front yard, but it does drop flower petals and the fruit (nutlets) that follow. Why not consider a hackberry tree? Also, the new elm introductions have been selected for their Dutch elm disease resistance. Other trees you might want to consider are autumn blaze (hybrid maple) or northern acclaim, which is a new seedless honey locust that grows fast and turns a beautiful yellow in the fall.

Q: We planted an autumn blaze in our yard about three years ago. This spring, we noticed green and red beads on the leaves. My husband thought he heard that this is a common disease in autumn blaze maples, but he's not sure if we're going to lose the tree. Can you give us some information on this problem? (e-mail reference)

A: This is an erinium mite infestation. These mites will not harm the tree. The problem will come and go through the years depending on weather conditions and a predatory mite population. There is no practical spray that can be used to control these mites, so just enjoy one of the minor curiosities of nature. The two organisms (maples and mites) evolved together a long time ago.

Q: I gave my wife some purple calla lilies a month or so ago. She planted the lilies in a pot. Are these the same as peace lillies? Can I plant them in my yard or are they better off in a pot in my house? Are these perennials or annuals? Should the lilies be planted in a shaded or sunny area? (Monmouth County, N.J.)

A: The peace lily is a spathiphyllum spp. It is appropriately named because of the spadix that is in the middle of the flower. The calla lily is a zantedeschia spp. that has flowers that are more cuplike. The lilies are better off in a pot in your house because you live in New Jersey. In the tropics, lilies are perennials, but in your part of the country, they would be dead after the first frost. They will take full sun or semishade.

Q: My rhubarb leaves have small red spots on them. What is causing this and how should I treat it? (e-mail reference)

A: Rhubarb leaf spots are not unusual this season because of all the cool, rainy weather we've been having. There are two fungi that have been identified as causing the problem, but they are not a cause for alarm. Ascochyta leaf spot infection first appears on the upper leaf surface as small, green-yellow, irregular spots that are less than 1/2 inch in diameter. The leaf develops a mosaic appearance as the lesions unite. Later, the spots develop white centers surrounded by reddish margins that are bordered by a grey-green zone. Reproductive spores develop deep in the plant tissue, so they are rarely seen in the spots. In a few days, the infected spots turn brown, die and fall out. This produces a shot-hole appearance. Aschochyta does not cause stalk infections. Ramularia leaf spot appears as small red dots that gradually enlarge to form circular lesions 1/2-inch or more in diameter. Larger spots become white to tan with purplish halos. The larger spots turn tan and become sunken lesions in the stalk tissue. Stalk infections occur later. The lesions appear as small spots that elongate as the stalk grows. White fungus develops in the center of the spots on the leaves and stalks. The white turns brown as the tissue dies. In both cases, it is best to remove the infected stalks and leaves. Usually, fungicides are not needed. However, if the disease has progressed too far and removing the stalks and leaves is not practical, then applying a copper-based fungicide is recommended. It also might be a good idea to divide the plants if they have been in one place for more than five years.

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 ronald.smith@ndsu.edu.


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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