Cover crops for home gardens

What each cover crop does, when to sow it, and when to cut it down.

A cover crop holds soil over winter, feeds it when you turn it in, and crowds out weeds. Legumes such as crimson clover and hairy vetch add nitrogen; grains such as winter rye and oats add the most organic matter; tillage radish breaks up compacted soil; buckwheat fills a summer gap in about 6 weeks. Cut or turn them under before they set seed, and give the bed 2 to 3 weeks before planting.

Plant	When to sow	What it does	When to cut
Buckwheat	2 weeks after last frost	The speed cover — from bare soil to dense canopy in thirty days, and a weed problem if you wait too long.	Usually 30–40 days after sowing — aim for 7–10 days after the first flowers open.
Crimson Clover	8 weeks before first fall frost	A winter-annual legume that fixes nitrogen and builds soil before the spring garden begins.	Fall-sown stands usually reach early bloom in mid- to late spring; spring sowings in about 60–90 days.
Field Pea	4 weeks before last frost; 8 weeks before first fall frost	A cool-season legume that fixes nitrogen, suppresses weeds, and feeds the soil — if you terminate it at the right moment.	Spring sowings bloom about 60–90 days after sowing; fall-sown stands in zones 7+ bloom in mid- to late spring.
Hairy Vetch	8 weeks before first fall frost	A cold-hardy legume that fixes a hundred pounds of nitrogen per acre when paired with winter rye — and becomes a persistent weed if you terminate it too late.	Fall-sown stands usually reach full bloom in mid- to late spring the following year.
Oats	4 weeks before last frost; 10 weeks before first fall frost	The northern gardener's self-terminating cover crop.	Winter-kill ends it in cold zones; elsewhere, mow or turn it under in spring, 2–3 weeks before planting.
Tillage Radish	8 weeks before first fall frost	The biodriller — a cover crop that does what a subsoiler does, without the tractor.	Usually winter-kills after several nights below about 23°F; in milder zones, terminate in spring before it flowers.
White Clover	4 weeks before last frost; 8 weeks before first fall frost	The nitrogen-fixing perennial that can live between your garden beds for years.	Often blooms the first year from early sowing; mow in late spring and again in midsummer to stop seed set.
Winter Rye	4 weeks before first fall frost	The hardiest cereal cover crop — a weed suppressor that survives winters that kill wheat.	Mid to late spring, depending on zone; cut earlier, before knee height, if the next crop needs moist soil.