Summary
A cover crop is grown to cover soil and may be incorporated back into the soil at a later point in time for enrichment. Some other benefits of cover crops include avoiding soil compaction, attracting pollinators, avoiding erosion, and suppressing weeds.
Planting Guidelines
Typically a cover crop is grown in late Summer or early Autumn until the first frost. They may begin growing again in spring. Before planting summer crops, turn the cover crops into the soil. Some cover crops fix high amounts of nitrogen, so by mixing them back into the soil you can avoid using synthetic nitrogen.
High Altitude Considerations
In high altitude environments, the growing season is already quite short, and properly growing a cover crop may be limited by the weather. Some options that work well in zone 4 are daikon, winter oats, winter rye, winter wheat, yellow, red, and crimson clovers.