Cover Crops for the Garden
Cover crops, often called green manures, protect empty soil between food crops. They reduce erosion, suppress weeds and can add organic matter when cut and incorporated or left as a mulch. Choose a type for the season, sow it promptly after harvest, and plan how you will clear it before spring planting.
Choose a cover crop to match the time of year and the job you need it to do. Fast-growing mustard can cover bare ground in late summer, while field beans and grazing rye suit colder months. Phacelia is useful in warmer gaps and produces flowers that attract insects if allowed to bloom. For a vegetable bed, avoid sowing a cover crop from the same family as the crop you will grow next, particularly where disease rotation matters. Read the seed packet for sowing months and final height. In northern and Scottish gardens, sow earlier in autumn because growth slows sooner than it does in milder southern areas.
Prepare the bed directly after a crop is harvested. Remove large weeds, diseased debris and spent plants, then level the surface with a rake. Do not over-dig if the soil is already loose, as the cover crop roots will help maintain structure. Scatter seed evenly at the recommended rate, rake it lightly into the top layer and firm the soil with the back of the rake. Water gently if conditions are dry, using a rose or fine spray so seed is not washed into corners. Label the bed with the crop name and sowing month. Check after a week and fill obvious bare patches if germination is uneven.
Use the cover crop as active ground cover, not as something to forget. Check it every few weeks for weeds, especially around edges where bindweed, couch grass and annuals can invade. Pull persistent perennial weeds promptly so they do not become hidden beneath dense foliage. Water young seedlings during an unusually dry spell, although established green manures usually manage without regular attention. If the crop grows tall or starts to flower before you are ready, cut it back with secateurs or shears. This prevents unwanted self-seeding and keeps the plants manageable. A dense canopy also reduces winter rain striking bare soil and helps protect its crumbly structure.
Decide how to finish the crop at least three weeks before you need the bed. For soft, leafy cover crops, cut the stems when they are young and chop them into small pieces. You can leave them on the surface as mulch or lightly incorporate them into the upper soil layer. For tougher crops such as grazing rye, cut before stems become woody and compost the tops if they are too bulky to handle. Do not bury large, fibrous masses immediately before sowing fine seeds, because they may interfere with seedbed preparation. Allow cut material time to settle, then rake a level surface for planting.
Use cover crops to fit a wider rotation. After early potatoes, peas or summer salads, sow a quick cover crop instead of leaving the soil bare until autumn. Before hungry crops such as courgettes or brassicas, clear the green manure in good time and add garden compost if soil needs further improvement. Field beans can be especially useful ahead of crops that appreciate fertile ground, but they are not a substitute for balanced soil care. Keep paths clear so crops do not spread into them, and do not let a green manure delay essential winter work. On an allotment, a labelled bed also shows neighbours that apparently rough growth is intentional.
Adapt the approach to containers and small spaces. In a large raised bed, sow a short-term cover crop only if it has enough time to establish and be cleared before the next planting. In containers, remove old annual roots, top up with peat-free compost and cover the surface with leaf mould rather than trying to grow a full green manure. Where winter is wet, a mulch may be more practical than a crop that needs clearing in spring. Keep notes on which species germinated well in your soil and weather. Over several seasons, you will find a dependable pattern for each empty bed.
Frequently asked questions
When should I sow a cover crop?
Sow as soon as a bed becomes empty and the chosen crop's sowing window is open. Late summer and early autumn are common times after vegetables are harvested. In cooler areas, sow earlier where possible, because short days and cold soil slow germination and growth.
Must I dig a green manure into the soil?
No. Cutting it and leaving it as a surface mulch is often easier and protects soil organisms. Soft growth can be lightly incorporated if you prefer, but allow time before sowing. Tough stems are best chopped finely, composted or removed after cutting.
Will cover crops stop all weeds?
They suppress many annual weeds by shading soil, but they will not eliminate established perennial weeds. Remove bindweed, couch grass and ground elder before sowing, and inspect the crop regularly. A dense, well-established cover crop gives the best weed reduction.
General guidance for UK home gardens and allotments. Conditions vary by region, soil and season; the RHS or a local garden centre can give site-specific advice. Page updated 19 Sep 2026.