NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
July 20, 2000
Ron Smith, Extension Horticulturist
North Dakota State University
Q: I have a row of 35 arborvitae (emerald I think). Upon inspection I have noticed that they turned brown within the middle leaving piles of dead needles. Also, I have noticed that some of the exterior tips have started to turn brown as well. I fertilized using a common brand called Woodacre. I then proceeded to apply a layer of cedar mulch. Unfortunately this is the extent of my knowledge. I am lover of all trees and flora and such and would hate to see these once beautiful trees wither and die, especially if there is a simple remedy. I am aware that there are many afflictions that can harm these trees, from over/under watering to diseases and insects. I am hoping that I might have a common problem such as watering habits. Sorry for the limited information but I am hoping you can give me some insight to the health and care of my trees. They have been in place for three years now and have grown to about 7 feet. (Long Island, N.Y., e-mail)
A: You probably have nothing to worry about. First, the accumulation of dead foliage in the middle is normal. "Evergreens" also lose their needles; some over a period of several weeks, others over a much shorter period, depending on the current environmental conditions.
Second, the tip burns could be the result of some esterification of volatiles from the cedar mulch. If the cedar had not sufficiently aged before being used as a mulch, that could be the problem. If it appears to progress, I'd suggest removing the mulch and stockpiling it for another season, then spread it again.
Q: I have tried to kill the increasing number of volunteer violets in my lawn for years with little success. I know you recommend Trimec, but it does not kill violets for me. Is there a solution? The commercial lawn sprayers in town say they cannot kill them either. I would dig them out, but at first I thought a few would be OK, now I have thousands. (e-mail)
A: What's the world coming to when Trimec doesn't take out violets! Perennial weed control in the spring is difficult anyway, and in the case of violets, impossible! Ask around to see if any lawn care companies have a product called Confront. It should do the job. If you cannot find anyone who uses this material, then get after the violets again in late August or early September. They are more vulnerable at that time of year, and the translocation of the Trimec would be most effective.
Q: We have a yellow poplar tree which is about 3 feet in diameter, so I'm not sure how old it would be. It has always been quite full until this year. Now half the tree is dead and on the other half the leaves are extremely small and the flowers are not filled out. We can't find any insects on the tree nor sign of disease. What could have caused this? What should we do to revive this tree? (e-mail)
A: The problem sounds like a disease of the vascular system or root rot. There is a disease known as Verticillium wilt that takes out poplar trees. The disease is soil borne and is very opportunistic. But that is only one of many. At any rate, the future of your tree is not good, and I suggest that you make arrangements to have it removed at your earliest to prevent property or personal damage. Trees that age often have internal decay that is not obvious from simple observation. Allowing a dead tree to languish on the property is simply asking for a disaster to happen. Don't allow yourself to be caught up in one!
Q: What’s the difference between snow on the mountain and snow in summer? A lady gave me some seed and said it was snow in summer or snow on the mountain. I don't have any more information from her than that. (Amidon, N.D., e-mail)
A: There’s a big difference between snow on the mountain (Euphorbia marginata) and snow in summer (Cerastium tomentosum). The former is an annual that is a member of the Euphorbiaceae family; it is poisonous if consumed and gets 2 to 2.5 feet tall with white flowers. The latter is a perennial that grows mat-like only to a height of 1 foot or less; it has nonpoisonous white flowers.
If you were given seed, I'm betting it was snow on the mountain, since snow in summer is usually sold as a transplant.
Q: When would I need to spray apple trees for both fireblight and insects? (Butler, P.A., e-mail)
A: Spraying apple trees for fireblight should be coordinated with weather conditions. As your area enters into a hot, humid spell, that would be a good time to spray for preventative measures. Check any fast-growing shoots for infection from the bacterium. It will be quite evident as you likely know. If a strong summer storm should blow through your area with high winds and hail that cause damage, spray within 48 hours after the storm has passed to provide protection.
Now, spraying for insects is something you should do only in response to a problem, existing or threatening. If you have trouble with apple maggots, you need to spray before the females lay eggs in the developing fruit, especially if you are growing Wealthy, Delicious or Cortland varieties. The best practice is good sanitation--cleaning up all old apples remaining on the tree or apple drops from previous years.
Check with your local county extension office to see what is labeled in Pennsylvania for spraying apple trees.
Q: Around a spot in our lawn where a damaged elm was removed a year ago we've got a lot of mushrooms. The recent rains have brought them up a couple of times a week. A neighbor says the chips from the tree have helped the fungi to grow. Interesting theory: Is it so?
The mushrooms aren't a problem. I just mow 'em. But they raise a question. Our lot produces a lot of limbs and branches every year. I'm thinking about buying a chipper to convert this stuff into mulch. But my enthusiasm for the idea will wane if putting the chips on our garden beds would nurture an extensive stand of mushrooms. A few of them are fine. Lots and lots aren't. Do you have thoughts or advice? (Bismarck, N.D., e-mail)
A: Get the chipper. Some mushrooms may come up as a result of using the chips, but your yard will not be covered in them. Yes, your neighbor is partially right. The "old" chips or other decaying organic matter in that old elm spot are contributing to the growth of mushrooms. I have them showing up on football fields that have not had trees growing in that area since I have been at NDSU. Mushrooms will grow on thatch, rotting roots, construction debris or dead bodies! Give us a week of warm, dry weather and they will be forgotten!
Q: I have one bunch of rhubarb growing within a couple feet of the garden. In the garden I have a row of peonies on the outside. Near the rhubarb the peonies are stunted and look unhealthy. Question: Does rhubarb do something to the soil that is possibly toxic? (Carrington, N.D., e-mail)
A: Yes, some plants do exude substances from their roots that are inhibiting or killing to certain other species of plants. This is called allelopathy; turfgrass has a similar effect on young trees;
large trees like black walnut have an effect on plants in the nightshade family especially. Dig either the rhubarb or peony up in the fall and replant somewhere else.
###
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