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Hortiscope

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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I’m wondering if the apple tree on my property that I bought several years ago is dying. I trim the dead branches from the tree and try to give it some room in the canopy. However, I think the tree is dying, but I’m not sure if it’s from disease or old age. My neighbors moved in about 15 years ago and the tree was here at that time. Is there anything I can do to save it? If not, do I need to wait to plant a replacement tree? Which varieties do you recommend for our area? I use the apples for juice, canning and pies. I also am sending you photos of the tree. (Moorhead, Minn.)

A: Thanks for the photos. Your apple tree is showing the typical symptoms of old age. Time and weather, insects, birds, squirrels and pathogens, plus the unintended abuse we humans inflict on trees, eventually will cause a tree to die. I would advise you to remove the tree when appropriate and replant with any number of cultivars. Zestar is a University of Minnesota introduction that is excellent for fresh consumption or cooking. The fruit will store for about six weeks. Regent and snowsweet also are good for the same purpose but will store for months if needed. The champion introduction from the U of M is the honeycrisp. More than 5 million honeycrisp trees have been planted.

Q: I planted 11 president grevy lilacs three years ago that I bought from a local greenhouse (I believe they came from Montana). The first summer after planting, they were healthy and looked like they were going to be OK. I planted them about 8 feet apart and the plants get full sun. I was told to pour the water to them so that they would establish a good root base. I have many different weeds growing because of the neighbor’s cow pasture. I put up a metal border and then used Weed King and Roundup on the ground between the lilacs. I was careful not to get any on the lilacs. After flowering last summer, the leaves began to curl. This year, I watered the plants four times a day for 30 minutes each time. I used the weed killers twice. The leaves are curling again and the new shoots and even older branches are turning black. I also have the same lilacs that I planted last summer in my front yard, but these plants do not have similar symptoms. I checked in some books that the NDSU Extension Service office had and found that my lilacs may have blight. I went home and trimmed out as many of the black branches and shoots that I could find and a friend sprayed them with a fungicide. Does it sound like blight? Am I watering too much? Will they survive the drenching? Did the weed killer contribute to the problem? Will they survive my obsession with weeds? Is there any way to keep the neighbor’s weeds from infesting my lilac bed? The weeds are bind and pig weeds, thistles and dandelions. (e-mail reference)

A: I assume you are not from North Dakota or Montana. The herbicides are bound to be having some impact on your plants, as are the heavy doses of water you are delivering to the plants. You shouldn't be watering the plants more than two to three times a week even under the most severe conditions. They only way you would is if you are growing them in pure sand on the top of a hill with no protection. Back off on the watering, reduce or eliminate the use of herbicides and allow the plants to get established. If weeds bother you as they do most people, use a physical barrier around the plants, such as heavy plastic sheeting topped with mulch. I would encourage you to get in touch with someone from your state’s Extension Service office for further assistance. Go to http://www.csrees.usda.gov/Extension/index.html and then click on your state, followed by the county where you live for a more local contact. Every state has a land-grant university with a plant diagnostic lab that can assist you in getting this problem nailed down.

Q: I am seeking information if amaranthus love-lies-bleeding is an invasive, seed-bearing plant in North Dakota. (e-mail reference)

A: I never have heard or witnessed any problems with this plant having invasive characteristics. We've grown it in our trial gardens here on campus with no problems.

Q: I was wondering what time in the spring is the best to spray for dandelions. I am in Idaho. (e-mail reference)

A: You should spray before they bloom, but that is nearly impossible with temperatures, wind and rain conditions. Consequently, 90 percent of the spraying activity is done when they are in flower because they are easier to see and the applicator gets the satisfaction of seeing the impact quicker. From a maximum control point of view, the best time would be in the early fall while the plants are in an assimilative type of growth and would take in a maximum amount of herbicide. This would give you a more complete kill.

Q: I'm looking at planting some hybrid poplars. They will end up being about 15 to 20 feet from my house. Is this OK or a waste of time? If I were to plant the poplars, how far apart should they be spaced? Are these trees cottonless? (Shepherd, Mont.)

A: Hybrid poplars have a place in the upper Midwest landscape plantings. However, planting the trees 15 to 20 feet from your house will end up being too close for my money. They grow fast and have an aggressive and far-reaching root and branching system. They tend to drop a lot of kindling as well when they begin maturing. Yes, they are supposed to be male clones, so the trees should be cottonless. I would recommend considering some other tree species than cottonwoods in this tight of a setting. Hackberry or bur oak would be a better choice because of the stronger wood structure.

Q: I have 40 cottonwood trees that are too tall. My yard is hemmed in on two sides and I get little sunlight. I cut one down that was 70 feet tall, but it’s far from being the tallest. Can we prune off the tops just after a limb and expect these trees to live and keep growing? (e-mail reference)

A: When you are dealing with this species of tree, it is something that should be left to a professional tree pruner because each tree is different when it comes to pruning. A lot depends on wood soundness, exposure and branching structure. There are other considerations as well. In a nutshell, yes is the answer to your question. I am assuming you are not looking for a tree that represents the typical characteristic of a poplar tree and the cutting does not result in a hat rack look to the tree. If that is the case, then you might as well have them removed. A certified arborist would take a more thoughtful approach by removing the dead wood and opening the canopy to allow for more sunlight to penetrate. This would help maintain healthy, vigorous trees. I assume you want these trees to be around for more than just another year or two, so the thoughtful approach would be to do canopy thinning rather than topping the trees. This will keep the trees aesthetically attractive for another decade or so.

Q: My daughter is a having her wedding reception in Stillwater, Minn., on May 22. The site is adorned with Japanese lilac trees. When do they bloom? (e-mail reference)

A: With luck, they may be in bloom by then. So much depends on the weather conditions. They are classified as blooming in early June in the north, but microclimates can push the date back or pull it forward. Let's hope it is an early, warm spring for a change!

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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