Q: I have been told not to use grass clippings sprayed with weed killer to mulch around plants. Can I use them after they sit in a compost pile?

A: Some plants, particularly tomatoes and young flower sprouts, are extremely sensitive to weed killers on grass clippings. Established shrubs and trees seem to be unaffected. If you compost the grass clippings, all chemicals should be gone after six months.