Types

• Soybean growing in a field replaces nitrogen other crops use.Soybeans image by bonjo from Fotolia.com
  
  Cover crops not only hold the soil in place but also improve the soil. Legumes, such as soybean or clover, are common choices. The same roots that hold the soil in place contain nodules of nitrogen-fixing bacteria that deposit nitrogen in the soil.
  
  

When

• Cover crops grow until a hard freeze.snowy dusk field track image by Alan Perry from Fotolia.com
  
  Generally, plant cover crops in the fall. As soon as the garden stops producing, till the ground and plant the seed. The cover crop grows until a hard freeze. The vegetation and roots act as an anchor keeping the soil in place even after they stop growing.
  
  

Considerations

• Do not let your cover crop become someone else's weed.Flower and Weeds image by Towards Ithaca from Fotolia.com
  
  Till cover crops into the ground in the spring before planting the next crop. This provides additional nutrients to the crop, as the cover crop decomposes. Some cover crops, such as hairy vetch, are invasive and should only be planted if you can keep them from spreading to your lawn or other adjacent plots.