Tables 2-4 list average planting dates, seeding rates, seed availability, and chance of winterkill for each crop. Planting dates, chance of winterkill, and management vary with climate. A longer season is available for planting and growing winter cover crops in the Willamette Valley of Oregon than in northwestern Washington. Mustard Late Aug. Their growth habits suit them as a cover crop.
Annual ryegrass is a turfgrass and can be more difficult to manage as a cover crop.
Its uses are more limited. Cereal rye is the most commonly grown cover crop in the Northwest. It is vigorous, very cold hardy, and can germinate and become established in cool weather. When planted by early September, rye will capture some of the available nitrogen in the soil and recycle it for the next crop. Rye grows rapidly in the spring and can become difficult to turn under by the time gardeners are ready to work their gardens.