How to Grow Winter Tares as a Cover Crop

Winter tares, also called hairy vetch (Vicia villosa), are one of the most cold-tolerant nitrogen-fixing cover crops available. They produce large quantities of soft leafy material, fix significant amounts of nitrogen, and grow vigorously in spring when temperatures begin to rise. They are an excellent choice for beds destined for hungry crops like brassicas, sweetcorn, or leeks, and their hairy-stemmed sprawling growth provides effective weed suppression once established.

What Makes Winter Tares Useful

The main advantage of winter tares is their combination of cold hardiness and nitrogen-fixing ability. They survive temperatures down to around -15°C when established, making them suitable for exposed gardens in cold regions where some other nitrogen fixers would not survive. The hairy, trailing stems interweave and form a weed-smothering mat that phacelia-style sprawling growth cannot match for density.

Winter tares also produce soft material with a low carbon-to-nitrogen ratio, meaning it breaks down quickly on incorporation and releases nitrogen in a plant-available form within two to three weeks of digging in.

When and How to Sow

Sow winter tares from August to October. August and September sowings give the best establishment and maximum nitrogen fixation by spring. October sowings work but produce smaller plants. Broadcast at 3–4g per square metre and rake in to about 2cm depth. Germination takes one to two weeks. The plants initially grow as upright seedlings before spreading and sprawling as they mature.

The Self-Seeding Risk

The most important management point with winter tares is to cut them before they flower and set seed. If allowed to seed, they become weedy volunteers throughout the garden in subsequent seasons. Monitor the bed in spring: as soon as growth accelerates and the plants show signs of forming flower buds, cut them down. Do not leave a stand of winter tares unattended past late April or May.

Incorporating Winter Tares

Cut or pull the material and dig in three to five weeks before planting. The soft stems decompose readily, especially if chopped roughly before incorporating. Winter tares produce more material than almost any other cover crop option in this sowing-and-incorporate cycle, so the organic matter contribution is substantial.

Combining Winter Tares with Winter Rye

A 50:50 mix of winter tares and winter rye is a classic combination. The rye provides structure, winter hardiness, and soil-stabilising roots; the tares add nitrogen and soft material. The mix performs better in heavy clay or exposed conditions than either species alone. Sow at a combined rate of 10–12g per square metre.

What Follows Winter Tares

Brassicas are the natural follow-on from any nitrogen-fixing cover crop. After winter tares, a brassica bed will typically show noticeably better early growth than one fed only with compost, reflecting the nitrogen released during decomposition. Sweetcorn and leeks also benefit strongly from the nitrogen flush.