Q: I have two windmill palms in my front yard. I covered them with large plastic bags to protect them from the cold. After a week, moisture covers the leaves, keeping them constantly wet. I'm not sure if I'm helping them or hurting them. — Steve Harris, email
A: Rip the bags off: Windmill palms are perfectly cold-hardy, down to zero degrees in some places. Moisture on the leaves will lead to disease.
Q: I have a dozen citrus trees in my garage. Last year one of my orange trees got hit pretty hard by spider mites, so I spray the trees with insecticidal soap every two weeks. But one tree's leaves are rolling up. — Mike Childers, email
A: Curling leaves are a sign spider mites are still present. The creatures suck leaf sap and cause the tissue to roll. A big spider mite population can cause complete leaf drop. Try donning a plastic glove and an old cotton sock on one hand and spraying it with neem oil. Wipe the backside of each leaf gently to coat it with oil and suffocate the mites. This method is least likely to hurt beneficial insects that might be present.
Q: Does the organic pest control method of steeping cut tomato leaves in water overnight and then spraying on plants work? — FF, email
A: I've heard of gardeners doing this, but no one has yet reported their results. Scientists have experimented with extracting solanine and tomatine from tomatoes and using these chemicals as insecticides. They kill insects, but not as effectively as nicotine, which tomato leaves also contain, though it is more concentrated in tobacco leaves.
As a side note, several vegetables contain nicotine, including cauliflower, eggplant and potato. When I was in Cuba, I saw farmers soaking discarded tobacco stems in water overnight, straining it, then using the liquid spray on eggplants. Their eggplant leaves had absolutely no flea beetle damage, which we yearly dread in Georgia.
Lots of garden plants contain chemicals that kill insects besides the aforementioned nicotine and solanine. Yaupon holly has caffeine, peppers contain capsaicin, catnip makes pulegone, lemons have limonene, chrysanthemum has pyrethrin, and cloves produce eugenol.
You’re welcome to try the tomato leaf insecticide, but remember that the liquid can possibly spread disease to tomatoes, peppers, eggplants and potatoes.
Q: I listen to your radio program on the Internet. My uncle has a pecan tree that has never produced any pecans. He says it's a male pecan tree and wants to cut it down. My advice was to give it a good dose of fertilizer this spring and see what happens. — Michael Morrow, Los Angeles
A: You have listened well, grasshopper! Well-timed and effective fertilization is the best way to kickstart a pecan tree to bear more nuts. There is no such thing as a male pecan tree; they all pollinate one another. I have detailed notes on growing pecans at bit.ly/GApecan.
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