Kinzler: Tree decline, more Bigfoot, cold mulch and hydrangea pruning
In today's "Fielding Questions" column, Don hears from a reader with basswood woes wondering why the plants seem to be struggling.
Q: I have two basswood trees in my backyard that appear to be struggling this year. Normally they are very full with leaves, but this year they were sparse. Also, the leaves have bumps on them and there are small holes in the bark. — Pauline D.
A: Bumps on tree leaves are usually galls caused by mites and don’t often affect a tree’s overall health. The thin leaf canopy of your basswoods is most likely the result of the holes in the tree trunk.
Sapsucker woodpeckers create neat rows of holes in which tree sap accumulates for them to drink. A hole or two is less cause for concern, but when they drill a continuous row, it interrupts the flow of water and nutrients up and down within the tree’s system. Decline in tree growth results, and death can occur if the sapsucker’s activity continues.
To halt the problem, it’s necessary to break the sapsucker’s habit. Wrapping the area of activity with burlap, if reachable, has proven successful. Or apply sticky Tanglefoot, available at garden centers. Balloons, aluminum pie tins and other scare devices have mixed results. It’s possible for trees to recover, depending on the extent of damage, and if additional injury is prevented.
UPDATE: In last week’s column, we shared the fascinating question of a Bigfoot lookalike that ended up being wild cucumber vines totally obscuring whatever object they were climbing upon. I asked the Roeslers, who are from Leonard, N.D., to check under the humongous vine, if they got a chance, and let us know what they found.
Kent and Deb responded back, and found a poor, weak tree underneath, which the massive vines were using for support. Bigfoot remains at large. — Don Kinzler.
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Q: With the recent cold weather, should I cover the perennials I planted this fall with mulch? — Dean S.
A: With the unusually cold weather, it's a good idea to mulch around the perennials that were planted this fall. Many parts of the region have already received snow, which insulates the ground also. The snow isn’t likely to remain, though, which will leave the soil bare.
Adding a layer of mulch over perennials and bulbs that were planted this fall, especially those planted late, prevents cold from entering the soil quite so soon, giving a few extra weeks for the perennials to settle in before the soil freezes solid. Twelve to 18 inches of leaves or straw is usually enough to allow at least two extended weeks of unfrozen soil. The mulch can be left in place until early next spring, and then removed in late March or early April.
Q: I have a huge hydrangea bush and I’ve read conflicting articles on when to trim them back. Is it better to trim them in the fall to prevent the snow from snapping them off? If so, how short should they be trimmed back? — Sandy T.
A: Hydrangea pruning differs between the two types that are adapted to our region. The round-flowered Hydrangea arborescens, often called Annabelle types, die back each winter to near ground level. Their pruning consists of cutting back the stems in spring to about 6 inches above ground level. Pruning is best delayed until spring, except to possibly remove the large flower clusters, as they can tend to weigh down the branches under heavy snow. Winter branch breakage is less problematic, though, because spring growth arises mostly from near ground level anyway.
The other category of adapted hydrangeas are the panicle types, Hydrangea paniculata, with cone-shaped, pyramidal flower clusters. Instead of dying back each winter like the Annabelle types, panicle types act like "normal" shrubs, leafing out from the upper branches each spring. Pruning in spring can be done to shape the shrub. Limit fall pruning to removing the old flower heads, which can break branches if they become snow-laden.
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.