When to sow broad beans

Broad beans are the hardiest beans you can grow and like a cool start. They germinate in soil from about 37°F, so they can go in far earlier than French or runner beans. In Germany, Austria and Switzerland the usual window is mid-February to the end of March, as soon as the soil has thawed and dried enough to work. In the UK, sow outdoors from March to May.

The earlier you sow, the better. Plants that have flowered before the summer heat set more pods and are stronger by the time black bean aphids build up in late spring.

In mild UK gardens and on sheltered, free-draining sites, you can also sow a hardy variety such as 'Aquadulce Claudia' in October or November. The plants overwinter small and crop in May or June, weeks ahead of spring sowings. They cope with light frosts, but hard, bare frosts and wet winter soil kill them, so in colder parts of Central Europe the spring sowing is the safer choice.

Short of space outside or plagued by mice? Sow in pots under cover from late January or February and plant out in March.

Broad beans like a sunny spot and a fairly heavy, humus-rich soil that holds moisture but doesn't waterlog. They prefer neutral to slightly chalky ground; on acid soil, lime the autumn before. Dig in compost before sowing.

Push each bean 2–3 in deep, with 6–8 in between beans. Leave 18–24 in between rows, or grow them in double rows 8–10 in apart with a wider path to the next pair. The big seeds carry plenty of reserves, which is why they can go so deep.

In a 120 × 80 cm raised bed, two rows along the long side about 16 in apart hold 12–16 plants. Tall varieties shade their neighbours, so put them on the north side.

Keep the rows weeded while the plants are young. Water in dry spells once the plants flower and again two weeks later; before that they rarely need it.

Most varieties grow tall enough to flop in wind and rain. Put a stake at each end of the row, or every metre or so, and run string along both sides at about 12 in intervals as the plants grow.

Once the lowest flowers have set small pods, pinch out the top few centimetres of each stem. The plant then puts its energy into the pods, and you remove the soft tips black bean aphids like most.

Spring-sown beans are ready in June and July, roughly three to four months after sowing; autumn sowings from May. Pick when the pods are full but the beans inside are still small and soft. Check one: the scar where the bean joins the pod should be white or green. Once it turns black, the beans are starchy and tough.

Very young pods, around 2 in long, can be cooked whole. Pick regularly and the plants keep producing for a few weeks. When they are done, cut the stems at ground level and leave the roots to rot in the soil.

Black bean aphid (blackfly) crowds onto the soft shoot tips from April to August. Early sowing and pinching out help most; squash small colonies or pinch off badly hit tips. Ladybirds and hoverflies usually catch up, and even hit plants still give edible beans.

Chocolate spot shows as small red-brown spots on leaves and stems and spreads in cool, damp, crowded conditions, on autumn sowings from late winter. Give the plants room and air, and clear away infected plants at the end of the season. Broad bean rust, with rusty-brown pustules, usually appears around flowering time.

Pea and bean weevils notch the leaf edges in spring but rarely matter. Mice dig up freshly sown beans; pot-grown plants avoid that.

Broad beans are legumes, like peas and other beans. Leave at least three, better five, years before any legume grows in the same bed again.

Traditional mixed-planting tables pair broad beans with potatoes and advise against peas, onions and garlic, and fennel. We found no trials behind these pairings; they are gardening tradition. Keeping peas apart does make sense for rotation, because they share soil-borne diseases.

One genuine health note: people with the inherited enzyme deficiency G6PD deficiency can react badly to broad beans, a condition called favism. Everyone else can eat them freely.