Establishing Birdsfoot Trefoil or Crownvetch as a Living Mulch Crownvetch seedling growth is very slow, normally requiring 2 to 4 years to produce a well-established, vigorous stand. Birdsfoot trefoil, on the other hand, establishes more quickly, so it is seeded with crownvetch to provide quick cover until the crownvetch becomes well established. The conversion from birdsfoot trefoil to crownvetch may take 3 to 5 years.
Few growers can afford to take a field out of production while the cover crop is being established.
Perennial weeds, especially thistles, hedge and field bindweed, hemp dogbane, horsenettle, common milkweed, and woody perennials, are hard to control without legume cover crops but even more difficult with them. This usually is possible only after small grains or on conservation reserve land. Accent, Basis, and Lightning have been found to be safe on crownvetch and birdsfoot trefoil and help control some of these problem weeds in corn. A year before seeding the cover crops, apply lime to raise the soil pH to 6.2 to 7.0, and apply phosphorus and potassium to nourish both the crop and the cover crops. Make seedings with a broadcast seeder to the soil surface.