December 6, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Hopefully this specimen from a hackberry tree will not be pulverized by the time it arrives in Fargo. This fall after the leaves dropped I noticed some branches with fungus-like growths. They all look brown and dry and are scattered in small clusters on the tips of the limbs. Any information would be appreciated. (Mitchell, S.D.)

A: Your sample of witches’ broom on the hackberry arrived in perfect condition. This is not a fungal disease but an infestation of Eriophyes celtis, a mite that feeds on the tree’s buds. Control is not normally recommended, but if you think it is necessary I suggest spraying with dormant oil next spring, before bud break. A follow-up spray with Sevin insecticide as the leaves are beginning to form is recommended. This is a natural host-mite relationship. Normally the witches’ broom doesn’t get to the point when spraying is necessary.

Q: I would like to know how much of my snowball bush I can cut off. It is as tall as our house. Is it all right to cut it off to the ground or at a 3- or 4-foot level? (Jamestown, N.D.)

A: Wait until a killing frost and then prune them back right to the ground. You will get no flowers next year (assuming you are talking about a viburnum) but it should flower in subsequent years. Make sure the canes are not coming from below any graft. If they are, cut them off at the source; if they are not, then prune them as you mentioned.

Q: Do you know if there is a use for small (about baseball size) cabbage heads at high end restaurants, etc. These are nice hard, dense heads. There are some in our patch that won't mature much larger than that before frost. Just curious! (Cando, N.D.)

A: I can’t believe there isn’t some kind of use for them. I'd certainly try selling them to restaurants, especially where there are ethnic groups from Slavic countries. Give it a try. What do you have to lose?

Q: I have several peonies that are about 10 years old. This year two of them have curled yellow leaves and look as though they are dying. Is there anything I can do to save them? Can I plant new ones in the same holes? (Fargo, N.D.)

A: Dig them up and divide them, assuming the crowns are still healthy. If not, pitch them. Planting in the same holes could be risky if the cause of death was a disease and not environmental or chemical. If they must be replanted in the same spot, then I would suggest excavating a good portion of the soil and replacing it with some fresh material.

Q: I have a large silver maple, about 35 years old, in my back yard. It is preventing any sunlight from getting to a large area of the yard and some branches are resting on my buildings and my neighbor's. I would like to have major pruning done that would remove about a third of the tree's branches. What time of year should this would be done? (Detroit Lakes, Minn.)

A: Silver maples and other large trees are best pruned in the late winter or early spring. Maples have a propensity to "bleed" sap when cut at that time. Don't let this concern you; the tree will not bleed to death. Pruning now should be confined to anything that could be a threat to property or bodies. Pruning cuts this late in the season will not have a chance to heal properly as they would in the early spring.

Q: When spring comes we often see or have juniper trees that are brown. From what I understand there is a spray that can be applied in the fall to help prevent some of the browning. I was wondering if this spray is called anti-desiccant and how and when should it be applied. (Steele, N.D.)

A: The anti-desiccant that is commonly found on the market is Wilt-Pruf. It should be sprayed on when the plants have been "shut down" by a series of autumn frosts, but when the air temperature is in the mid-forties or higher. A re-application is strongly recommended in the late winter or early spring on one of the "thaw" days. What often happens is the soil is either still frozen or so cold that water cannot be transported to the aerial tissue, which is being dried out by the warmer spring winds. A spray then would help prevent that as most if not all of the fall spraying has either washed off or broken down in the winter sunlight.

Q. I have seen a beautiful plant that someone told me is called lythrum. I have tried to locate it in a local nursery, but no one handles it, and someone told me that it is illegal to grow it anymore. Is there any truth to this? (Jamestown, ND)

A. Unfortunately, yes. This beautiful, durable plant that is not a native species has adapted too well to our North American environment, and is choking many of our waterway systems, wiping out natural food source species like cattails. So lythrum, or purple loosestrife as it is also known, is on the state's prohibited noxious weed list, which means that all such plantings should be eradicated. Resist being tempted by this plant, and know that you are doing our prairie environment good by not growing it.

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. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu