Gardening glossary
Cover crop
A cover crop is anything you grow specifically to feed the soil rather than to feed yourself. The bed never sits bare. Between summer vegetables and the next spring planting — or wherever there is a gap of six weeks or more — a cover crop puts living roots in the ground, protects the surface from rain and sun, and either fixes nitrogen or stockpiles organic matter that the next crop can draw on.
The main families:
- **Legumes** (clover, vetch, field peas, fava beans) host *Rhizobium* bacteria in their roots that fix atmospheric nitrogen. After incorporation, much of that nitrogen becomes available to the next crop. - **Grasses and cereals** (rye, oats, barley, wheat) produce huge volumes of fine roots that build soil structure and suck up leftover nitrogen so it does not leach over winter. - **Brassicas** (mustard, daikon radish, kale) break up compaction with their deep taproots and have biofumigant compounds that suppress some soil-borne pests. - **Mixes** (a legume + a grass + a brassica) combine all three benefits.
How to use cover crops in a home vegetable garden:
1. **Autumn sowing.** Crimson clover, hairy vetch, winter rye, or fava beans go in 4–6 weeks before your first hard frost. They overwinter, then green up in spring. 2. **Termination.** Two to three weeks before you want to plant the next crop, cut the cover crop down with shears or a strimmer, leave the residue on the surface (no-dig) or shallowly turn it in. 3. **Resting period.** Let the biomass break down for at least two weeks before planting — fresh green material can immobilise nitrogen as it decomposes.
A small bed sown with crimson clover in October and turned in in March can supply 50–100 kg N/ha worth of nitrogen — enough to skip the next spring's fertiliser application. Pair this with [no-dig methods](/glossary/no-dig) to compound the benefit.