I found a white powder-type substance on the stems of tomatoes as well as coneflowers (not located near each other). What is this? How do I get rid of it, or can I? Can we still eat the tomatoes?

This is a big year for planthoppers. The fuzzy material you see is a protection produced by immature planthoppers, known as nymphs. Pull some fuzz apart and you may find a nymph but, more often than not, they have already abandoned ship. No action is necessary.

I have a bunch of big cuttings from a friend’s overgrown rugosa rose bush. My wife is concerned that birds will spread the rose hips to the extent they become invasive. All the open areas around here are mown to keep down the multiflora rose, which I know is invasive. I really like the idea of planting rugosa roses along a bank by the road, in the hope they replace the weeds and deter trespassers. They are good for erosion control and are salt-tolerant, too.

Rugosa roses are not considered invasive in Maryland, and we do not see any research indicating the rose hips would cause a problem by aggressive seeding. We use the term invasive to mean hyper-aggressive non-native plants destructive to native plants and wildlife. Though not invasive, rugosa rose is known for its aggressive suckering habit and will spread (by roots) to colonize large areas when not kept in check. If your goal is to create a dense, protective hedge, then this plant will certainly do the job. Mow around it to keep it contained.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.