Field beans

Vicia faba

Field beans are a winter green manure, a crop you grow to dig back into the soil. Sown in autumn, they cover bare ground through winter. Their roots open up heavy soil and like all beans they add nitrogen. Dig them in during spring, before the next crop.

Looking after it

Water: Field beans need very little water. Autumn and winter rain is enough, so only water if the soil is dry when you sow. Feeding: They need no feeding at all. They make their own nitrogen and it stays in the soil for the next crop.

Cutting and digging in

In spring, any time up to flowering, cut the plants down. Chop them up and let them wilt, then dig them into the top 25 cm of soil. Wait about a month before you sow or plant anything in that bed.

What can go wrong

Blackfly. In spring, thick clusters of black aphids sit on the shoot tips. Usually you can leave them, as the plants will be dug in soon. If they spread, cut the plants down a little earlier.
Slugs and snails. They shelter in the thick cover and then move on to the next crop. After digging in, protect young plants and check for slugs on damp evenings.

Growing facts: RHS, UC ANR and seed-company sowing guides. Green manure care: RHS. pH: Oregon State University extension.