Uprooting wisteria, and other nonnative plants

Ordinarily, the first course of action I would recommend would be to cut down or mow the shoots continually until the plant weakens and eventually dies. This process requires tenacity and can take several years, but since you've already tried this without success, it's time for plan B.

All those baby sprouts you're seeing are originating from the underground roots of the mother plant, even though you cut it down. The best way to control its offshoots is to kill it at the source. Return to the stump and, using a 1/8-inch bit, drill inch-deep holes about a quarter-inch apart all over the surface of the cut trunk and carefully pour a liquid weed killer, such as Roundup, into each hole. The roots will transport the herbicide to the offshoots. If any of the offshoots are larger than an inch in diameter, they should be treated in the same manner. Extreme caution should be taken when applying the herbicide because it has the potential to kill every plant it contacts, including grass, shrubs, perennials and trees.

A reader from Hampton Bays wrote to you recently and mentioned he had his trimmed on top two years ago. I have been advised that it will ruin the trees' cylinder-shaped top and make them unattractive. Will the trees eventually regrow their pointed tops? If we decide to go through with the trimming, how much should be trimmed? I would like to have at least 2 feet removed. --Mary Shorthouse, Westbury

That was accomplished all right, but the rope, which was very thick, removed a nine-inch section of bark from the tree. I had heard that a tree will die if the bark is damaged. Should this bark damage be covered with pruning sealer? --Joan, Wading River

There is one vertical section of bark depicted in your photo that appears to be quite deep, but the rest, assuming the other three sides of the tree are not affected, doesn't seem insurmountable. To prevent the tree from further stress and facilitate healing, it's important to keep it watered and give it a boost with a slow-release fertilizer applied under the drip line of the tree (take care to avoid allowing the product to come into contact with the trunk). You should also clean up the jagged edges of the wound using a sharp knife to score a shallow area outside the perimeter of the damage. This will help the tree heal itself more rapidly.

Pruning sealer could actually encourage decay, so it's best to avoid using it.