Q: We bought a sycamore tree from a local nursery 30 months ago. The first summer it started out healthy, but it soon began to develop brown edges on the leaves. The leaves eventually fell prematurely. The second summer was similar, but worse. And now this year, it has been worse still. Friends tell us they think it has anthracnose. If it has that fungus, did it come home from the nursery with it? What might we do now?

A: Anthracnose is a fairly common disease on older sycamores (occasionally younger ones). You can find hundreds of photos online showing the unusual dieback patterns it causes on affected leaves and branches. (Tip: add the word “pathology” into your online search, and it will take you to university websites where you'll find the most reliable information.) If most of what you saw was simply marginal browning, I would suspect drought. It only has to happen one time.

If it is anthracnose, that disease is widespread, and I wouldn't think that it came with the plant from the nursery. However, I'm sure they'll work with you in determining if that has been the cause and, if so, what the best remedy might be. Actually, choosing another shade tree might be the best long-term solution. Again, a local independent retail nursery could help you with that.

Q: My azaleas are struggling from the extreme heat in the Texas summer. When can I prune out dead wood to make them look better?

A: Dead branches and twigs can be pruned out of any plant at any time. The only time-sensitive pruning you would do to azaleas would be if you wanted to reshape the plants for the new growing season. That trimming would be done immediately after the spring bloom had finished.

Q: I have an area in my landscape where I used a pre-emergent weedkiller mixed into the soil to prevent birdseed from germinating beneath feeders. The weeds are still there, but my mondograss, petunias and even Double Knockout roses are dying. Is there something I can add to the soil to neutralize the weedkiller, or do I need to replace it?

A: Time will eliminate the remnants of the herbicide. It will gradually leach out of the soil following rainfall and irrigation. For the record, there is no need to put pre-emergent weedkillers into the soil. They are attacking the seeds as they sprout at the surface. Another comment worth making: pre-emergent weedkillers, if chosen and applied correctly and at the proper rates, should not be affecting plants that are already growing. It sounds like one or more wheels came off the bus.

Q: I have been searching for information on how to grow a pineapple from the top of a fruit. However, what I haven't found is how to water the plant while it's covered with plastic. Suggestions?

A: You're already miles down the journey. Let's bring everyone up to speed. The top of a pineapple fruit can be planted into a pot filled with lightweight potting soil. If kept moist, it will develop roots and begin growing. After 12 to 18 months, it will be 24 to 30 inches across. At that point, an apple core can be placed down into the crown of leaves and the plant covered with several layers of dry cleaner's plastic to keep it airtight. The apple will give off ethylene gas as it decays, and that gas will trigger the flowering process. After five or six weeks you can remove the plastic and wait for the flower to form. Should the plant get dry during that time, merely soak it in a tub of water for a couple of hours.
