Hairy Vetch One of the better legumes for improving worn out soils or adding a natural nitrogen source. Will stay green all winter long if weather is mild. Vetch does not require a fine seed bed. Just a little loose soil is all that is needed. Sow vetch seeds, 40-60 days before expected killing frost date. This will give it time to get established. Sow at the rate of 1.5 lb./1,000 sq. ft. or 60-65 lb./acre. When vetch is 8-10″ tall, till under.