ASK THE GARDENERS. Questions & Answers
Q We sowed some crown vetch seed last year on a bank in back of our house. Only a small amount came up and we have been trying to keep it free of weeds. We thought by this time we would have a thick ground cover. The pictures in the advertisement showed beautiful pink flowers covering the ground. What went wrong?
Crown vetch (Coronilla varia), a legume, needs to be nursed along for a couple of years or more, until it is established. It needs a loose seed bed and prefers alkaline soil. Seeds should be mixed with an inoculant to introduce what are called nitrogen fixing bacteria, which in turn allow tubercles on the roots to use nitrogen from the air, promoting good germination and growth. Inoculant should be available from seed sources. If germination was poor, you may need to scratch some areas up with an iron tooth rake and reseed. If your bank is very steep, you may need to use some erosion-preventing mesh or netting, or straw, over the seeding. It should be kept moist.