Rainline Garden
Winter Cover Crops for Northwest Vegetable Beds
Why to sow cover crops in empty beds each fall, which ones grow well in Oregon and Washington, and how to turn them under in spring.
West of the Cascades, a bare vegetable bed spends the winter getting pounded by rain. That rain compacts the surface, washes away fine soil and leaches nutrients down past where roots can reach. A cover crop sown in early fall protects that bed all winter, and in spring you turn it into food for the soil.
What a cover crop does
- Protects the soil from heavy rain and erosion.
- Adds organic matter when you turn it under, which improves drainage in clay and water-holding in sandy soil.
- Holds onto nutrients that would otherwise wash away over winter.
- Adds nitrogen, if you grow a legume such as clover, peas or favas.
- Smothers winter weeds.
Good choices for Northwest gardens
- Crimson clover. A legume with striking red flowers in spring. Easy for home gardens and fixes nitrogen.
- Austrian winter peas. A cold-hardy legume, often sown mixed with a grain for support.
- Fava beans. Large-seeded and easy to sow by hand. Grow them as a cover crop, or let some mature for a spring harvest. See fava bean timing.
- Cereal rye. Very hardy and great at holding soil and smothering weeds, but it grows tall and tough in spring. Cut it early.
A mix of a legume and a grain, like peas with cereal rye, combines nitrogen with lots of organic matter.
When to sow
Sow as early in fall as you can clear a bed, ideally from late summer through about early October west of the Cascades. Legumes in particular need time to establish before the cold. Late sowings still help, but give less growth. In colder east-side areas, sow earlier, and choose very hardy options like cereal rye.
Scatter the seed over loosened soil, rake it in lightly, and water if the fall rains haven't started. Covering seed with a thin layer of soil also keeps birds from eating it.
Turning it under in spring
Cut or turn the cover crop under in spring, ideally when legumes start to flower and before any of it sets seed. Chop it with a spade or cut it at the base, then dig or fork it into the top few inches of soil. Give it two to three weeks to break down before planting. Fresh green material can tie up nitrogen and get in the way of small seeds for a short time.
No room for a cover crop? A thick layer of shredded leaves or straw over the bed also protects the soil through winter. Garlic, which goes in each fall, can share space with mulch too. See how to plant garlic.
Garlic
