Horticultural Questions and Answers for Upcoming Summer

My ash, elm and caragana look dead. Should I cut my tree or shrub down right away and be done with it?

On April 19, Fort Benton temperatures were as high as 76 degrees. On April 29, Fort Benton temperatures were as low as 13 degrees. Many buds were destroyed from extreme rise and fall in temperature. Below is a response from Dr. Cheryl Moore Gough (Retired MSU Horticultural Extension Specialist). Severe temperature fluctuations in April have damaged buds of many deciduous trees and shrubs. The trees appear to be dead. Deciduous trees should be given time to struggle through and recover. Many have secondary buds that are formed for just such an event, and may yet leaf out. Use a thumbnail to shallowly scrape into the cambium of the branch. If it is green, the branch is alive and needs to be given time to recover. Another test is the suppleness of the branch. It is recommend folks give their trees until at least the 4th of July to recover from such a winter, and sometimes even longer if the branches still appear to be alive. Dr. Peter Kolb (MSU Extension Forester) recommends waiting at least one year before firing up the chain saw.

Are rhubarb leaves toxic?

Yes, the leaf blades of the rhubarb contain oxalic acid in quantities sufficient to cause human fatalities if they are ingested. Instead, cut the blades from the leaf stalks and eat only the plant stocks.

Are chokecherry trees toxic?

Yes, until they are mature. Children and livestock have been poisoned by ingesting leaves, seeds and stems. The inner bark, buds, flowers, seeds and suckers of this plant contain the cyanogenic glycoside prunasin, which when digested by stomach enzymes results in cyanide poisoning. The plant is most toxic in spring and summer. Leaves become relatively nontoxic when fruit mature.

I have brown bur-like clumps growing in my ash trees. What are they and how do I get rid of them?

The clumps are galls created by an eriophyid mite, and the damage is commonly called ash staminate flower gall. Galls can be caused by insects, mites, bacteria, fungi, nematodes and mechanical damage. Gall mites spend the winter under the flower buds

and begin feeding and laying eggs in the developing flowers in spring. The ash tree, in response to the mites feeding, grows new malformed plant tissue (gall) around the mite. The galls in turn provide some protection for the mite against weather, predators and parasites. The ash staminate flower galls remain on the tree for up to two years. The galls are green at first, and later turn brown to black within the growing season. Research has shown that this particular gall does not harm the tree’s health or growth rate. In extreme conditions, the weight of the galls can cause smaller branches to strain from the weight, which may to lead to breakage. This problem is rare and typically affects young newly planted ash trees. Miticides and horticultural oils can be used to help reduce mite and gall populations in ash. Information for this section came from Iowa State University Extension.

Montana State University, U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach.