Do I need to keep weeding in fall? There are only a few little weeds, and wouldn't it be better to spend my time, say, pruning?
A weed pulled in time saves nine — or 90. Many summer weeds are now loaded with thousands of seeds. Also, many weeds known as winter annuals start now and will explode with growth in spring. Hairy bittercress is one of these; it's is a tidy rosette now and almost a joy to pull, it's so easy. Because it has no seeds yet, you can throw it on the lawn and chop it up when you mow, adding organic matter to improve your topsoil. On the other hand, any weeds that are already covered with seeds should be bagged for trash. As for pruning, fall is not the right season. It can stimulate new growth that may be killed by harsh winter temperatures. A minor touch-up here and there is OK.
We have big patches of black stuff growing on the trunk of our oak tree. Is this a type of lichen? I know lichen isn't bad, but isn't it usually grayish green?
This is not lichen, it is the canker-causing fungus Hypoxylon. It interferes with tree "circulation," causing branches to die back and bark to slough off. In addition to oaks, it can infect other weakened trees and, unfortunately, will kill them. There is no cure. The key is to prevent stressful conditions. Protect your trees from drought, soil compaction and construction damage (especially trenching), and consider lightning protection on high-value trees. You might want to get your trees evaluated by an arborist certified by the International Society of Arboriculture, who are associated with many tree service companies.
University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information. Call 800-342-2507 or send a question to its website at extension.umd.edu/hgic.