As Fall Fades, Tips to Keep Your Garden Growing

A close cousin that does well in the Washington region as an annual is sweet marigold (Tagetes lucida). It is one of the few marigolds that emit a pleasant aroma, similar to tarragon, present in flowers and foliage. It is used as a tarragon substitute. Look for seeds now since it's not commonly found at garden centers in spring.

My daughter planted a long-needled pine seedling in my yard 24 years ago. Over the past several months some of the branches and needles have developed a black, powdery-looking, somewhat sticky substance on them, which is affecting a good bit of the tree. Some branches and needles are dying. How do I figure out what the problem is and how to treat it? -- Bill Beavers III

Your long-leaf or long-needle pine (Pinus palustris) is a southern pine growing farther north than its typical limit, southeastern Virginia. This means it isn't going to be a vigorous tree in the Washington region and must have been sited in moist, well-drained soil and full sun for it to have done so well for so long. This ordinarily problem-free southern pine will be susceptible to more insect and disease problems in our cooler climate. If the foliage appears to be covered with white flecks, pine needle scale is a likely suspect. With its long narrow shape, it is present primarily on the needles and feeds on all needle-bearing evergreen conifers. Pine bark adelgid also coats needles, stems and branches with white cottony masses. Insects that feed on the sap of a plant through its leaves and stems are aphids, adelgids and scale. They excrete excess sap (honeydew) they can't use. The sooty mold grows on this honeydew. Some twigs and branches may die.

Do a cleanup pruning (or have it done depending on the size of your tree). Prune dead wood and branches that have matted together because of webbing or wax from the scale insects or adelgids. Hose off sooty mold. Before growth begins in spring, spray tree with insecticidal soap and horticultural oil, such as Volck Oil Spray. This will begin to control insects that are weakening the pine. Never spray oil if temperatures are expected to be lower than 40 degrees within 24 hours of treatment. Apply oil and soap again when scale insects or adelgids are active. Two systemic insecticides that can be sprayed when you see the minute insects crawling are Isotox or Orthene. My preference is to use insecticidal soap and horticultural oil. Follow all labeled instructions and never spray on a windy day.

My goal is to continue producing enough food for my needs. I have used carpeting as mulch for 50 years. It has worked for me, keeping weeds out and holding moisture in the soil. Recently I stopped using carpeting. What can I put in its place? -- Max Sturman

Commercial landscape fabric is another permeable fabric that allows moisture and air in and prevents weeds from germinating. I prefer a two-to-three ply non-woven fiber that is spun-bonded and tough enough to be lifted when necessary. If aesthetics is one of the considerations, you might cover the fabric with mulch. Design the garden in a way that the rows are planted with a cool-season grass, such as rye that can be mowed in season and tilled into the soil when it's fallow. Use landscape fabric to cover only the rows of produce where you won't be mowing.

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail or contact him through his Web site, http://www.gardenlerner.com.