NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

June 17, 1999

Ron Smith, Extension Horticulturist
North Dakota State University

Q: I have a snowball bush, and I would like to trim the top down. When is the best time to do that, and will it hurt the bush? Will this stop the blossom from coming on the top? It is beautiful now, but I would like to keep it at a medium height. I really enjoy reading your column. (Walcott, N.D.)

A: The snowball (I assume you mean the Hydrangea) should be pruned in late winter or early spring, as it blooms on new growth. Unless you are willing to give up some flowers, now is not a good time to prune.

Q: Enclosed are four samples from my Colorado blue spruce that is losing needles and is a strange color. Can you tell me how I can save my trees? (Bismarck, N.D.)

A: Thank you for the good samples. Unfortunately, the news is not good. It looks like your trees are being hit by Rhizosparea needle cast, a fungal disease that can totally debilitate spruce trees.

Begin a spray program immediately with Bravo (chlorothalonil) and repeat every 14 days until September. Begin again next spring in May and repeat in June. Badly afflicted trees should be removed.

Q: I am enclosing a card with two bugs taped to it. These bugs are on my asparagus, but I have small black things sticking out of the spears. (Woonsocket, S.D.)

A: Thanks for somehow getting identifiable samples to me. I'm surprised they were not squashed in the mail!

You have two different species of beetles feeding on your asparagus. Since you are now past harvesting, spray with Sevin insecticide. Then in the fall, clean up any crop residue to prevent overwintering protection.

Q: Can you tell me what is happening to the ash trees this spring? So many of the new leaves are falling. Will they get new leaves? (e-mail reference, Aneta, N.D.)

A: The ash trees are being hit hard by a fungal disease known as ash anthracnose. It causes defoliation shortly after leaf-out, but then the tree does re-leaf a couple weeks later. It is usually not lethal to the tree, and there is little that can be done at this time of year.

In the fall, rake up all fallen leaves, and if the following spring appears to be coming on with a cool, wet spell, spray at bud swelling with lime sulfur and fertilize to promote vigorous growth. Two other sprays should be applied: one at leaf expansion, and the second about 10 days later, this time using Daconil 2787 fungicide at a rate of 2/3 tablespoon per gallon of water.

Q: In past years my rhubarb has grown thick stalks, but this year it is producing primarily spindly, thin fruit. What is causing this? (Killdeer, N.D., e-mail)

A: Rhubarb doesn't like to be kept in the same place forever, so when it gets sick of the location it is in, it lets us know by producing undersized petioles and leaves. Simply dig it up and move it to a new location. This needs to be done every six to eight years.

Q: I have an old submerged stump in my lawn. The area is full of mushrooms. Is there anything I can do to control or rid the area of the mushrooms? (e-mail)

A: Wait for it to dry out! Or get a stump grinder in and have it forcefully removed.

The mushrooms are simply visible evidence of nature at work, decomposing the old stump. The task should be completed in a couple of years. Sorry, but there is nothing that will selectively take out the mushrooms. Generally, they become inactive when the weather warms and dries out a little.

Q: Two years ago I cut down all the lilac bushes in the cemetery after the severe winter with all the snow. They had become so entangled that they were hard to clean. Now they have grown back to about 4 feet high and had beautiful blossoms this year. Here is the problem. The cemetery board wants me to cut them back to about 3 feet high now that they are done blossoming and square them off. Is this a good idea? (Selby, N.D.)

A: Not a problem to cut them back to a squared-off form. Doing it now will assure blooms next year.

I concede that the "boxed" lilacs will not look natural, but the board is obviously attempting to get the cemetery into a formal look.

The lilac flowers will still look and smell beautiful!

Q: When is the best time to trim a Russian almond since mine is getting out of hand? I also have a 3-year-old standard pear tree that leafed out nicely this spring, but then the leaves started to droop and eventually dry up. There is also a new shoot coming out of the trunk near the bottom. Should I leave the shoot to grow or wait for the tree to re-leaf? (e-mail reference, Hague, N.D.)

A: I don't think it makes much difference how or when you prune the Russian Almond since this species has a strong tendency to sucker. Prune it any way you wish to keep it under control, or move it to a location where it can grow to natural form and save you the trouble of trying to keep it in bounds.

Concerning the pear tree, it sounds as if a root rot has taken hold. The tree's leafing out is a result of what carbohydrates were stored there the previous fall. The fact that the leaves wilted is because nothing was coming forth from the root system or so little that it could not sustain them. I suggest waiting about 30 days, and if no releafing takes place, consider the tree dead.

About the sucker coming from the base: This may be a renegade shoot coming from a grafted root stock, which may or may not be a pear of desirability. You can let it grow for a while and see what takes place. If it isn't to you liking, then get it out of there.

I have not had good luck with pears in North Dakota. Something always seems to happen to them before I can get anything useful out of them!

Q: Enclosed is a sample of my grapevines that I have been having trouble with. In the spring the fruit looks like it is going to produce, but then they start to dry up. I can't believe it is the frost that is doing this. Can you please help me? (Wisconsin Rapids, Wis.)

A: After giving your sample a thorough examination under the microscope and digging through some references, my only conclusion is that something is causing your flowers to abort.

Here is my thinking. There is likely a lack of pollinating insects, or you are using Sevin insecticide as a preventative spray which is very toxic to the insects that carry out this task. Additionally, the Sevin may act as an embryo arborter to the grapes at a specific stage of development.

I could find no disease or insect activity or evidence. This is the best conclusion I can arrive at.

Q: Can you tell me what to do with spruce trees that are bleeding milky sap? (Cando, N.D.)

A: It is likely that your spruce has a progressive canker disease known as cytospora. All you can do is prune out affected branches and remove any trees that are overcrowded. Do all you can to promote vigor, fertilize, and don't cultivate under the trees.

Q: Can you tell me what kind of tree this is and how it got there? They look rusty. Will the rust spread to other trees, and what can we do? (Bowdon, N.D.)

A: You have something that was planted by the birds—a buckthorn! The spots you see on the leaves are rust, which has an alternate host in the cereal grains. Since we are in the prairies where a lot of cereals are grown, it is quite common in our region. Your sample was so badly infected and damaged by the rust that I wouldn't bother with any spray program. Rogue it (and any others in the area) out completely.

This is a species specific rust fungus and will not spread to your trees or shrubs.

Q: Can you tell me why the enclosed leaves from my silver maple tree are turning prematurely yellow with brown edges? (Glen Ullin, N.D.)

A: Your silver maple is a seedling selection which is showing an intolerance to our alkaline prairie soils by producing chlorotic (low chlorophyl containing) leaves. You can try fertilizing with iron sulfate or chelated iron to see if it will pull out, but I sincerely doubt it. This affliction is usually progressive until the tree dies.

Sorry about the bad news!

Q: Can you tell me what kind of plant this is and why it is turning brown on the ends? (Frankfort, S.D.)

A: Your plant is known as the prayer plant—scientifically known as Maranta lenconeura kerchoreana—a real mouthful! What you are witnessing is a salt or fertilizer burn. This could be from the water containing chlorine or fluoride, or fertilizer salts accumulating in the container soil. I suggest repotting in a humus-based soil (African violet mix), in a free-draining container, fertilizing every two months, and using distilled or rain water for watering.

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Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu.

Source: Ron Smith (701) 231-8161 ronsmith@ndsuext.nodak.edu

Editor: Dean Hulse (701) 231-6136