Q: There are multiple little bumps on most leaves on our 5-year-old maple tree. We’re thinking they’re eggs and we’re wondering how to treat the tree. — Angie K.
A: The bumps on the leaves are called maple leaf galls, and are caused by tiny mites that enclose themselves inside the hard growths visible on the leaf surface. I receive many questions about these throughout the summer, so I repeat the information periodically when I receive an influx of new questions.
Insecticidal sprays aren't effective at this stage because the mite is safely nestled inside the growths. There’s good news, though, because these galls don't really affect the tree's health. They’re mostly cosmetic, and leaves are able to carry on with photosynthesis just fine, unless leaves are grotesquely covered with bumps over two-thirds of their surface.
If an attempt at control is desired, the timing is critical. Apply horticultural oil to the tree trunk and major branches in spring just as leaf buds are swelling. Horticultural oil can be found at most locally owned garden centers.
Q: Over the weekend at our campground somebody peeled the bark off a maple tree from the ground up to about 8 feet. Is there anything we can do to save the tree? — Lonnie B.
A: Once bark has been peeled away from a tree, there isn't much that can be done to reverse the loss. Pruning paints and sealers have been shown to cause more problems than they were intended to solve, so they offer no help.
Whether or not a tree survives such damage depends on several things. If the bark was peeled away from only a small section of the trunk’s circumference, the tree will likely survive. If half the bark’s circumference is gone, the tree will probably die.
Damage also depends on the depth to which the bark was injured. If the outer bark was peeled down to the white wood, that trunk portion can no longer function normally. If the exterior of the bark was scarred without revealing the white wood, the impact will be less.
Unfortunately, there isn't a remedy, other than a wait-and-see approach. The leaves of a severely injured tree will begin to wilt within a week or so, depending on temperature.
Q: My potato plants are starting to bloom. Some varieties have white flowers and others have purple. My neighbor says you’re supposed to cut the flowers off. Is that true? — John L.
A: I’ve enjoyed growing potatoes since I was a young boy, and I’ve often wondered the same thing. Removing the flowers of some plants allows their energy to be directed to better use. For example, rhubarb flower stalks should always be removed as they appear so vigor isn’t robbed by the unnecessary flower and seed.
Removing the flowers as they form on potato plants is theorized by some gardeners to direct the plant’s energy into better underground tuber production. Does science support the theory?
I was able to locate several studies done by research universities, and the results of removing flowers did improve tuber yield in some studies, but not others. Researchers indicated the results tend to vary between different potato varieties and are affected by environmental factors like weather.
If pollination of potato flowers is successful, a round, green, ball-shaped, seed-bearing fruit is formed. Removal of any green seed balls that form seemed to have a greater effect in increasing tuber production, versus allowing the seed structures to remain.
So should we remove the flowers on potatoes, or not? Several research reports indicated the removal certainly doesn’t hurt potato production, and as long as there’s a possibility of increasing production on certain varieties under certain conditions, removal might be worth a try.
If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at firstname.lastname@example.org. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.