Why French beans wait for warm soil, and when to sow them

French beans are tender, so wait until the frosts are over. In the UK, sow indoors from late March to late April, or straight into the ground from early May to early August. Plant out indoor-raised beans from early May to early June.

They’re quick, around 50 to 70 days from sowing to the first pods, and a row crops for about eight weeks. Sowing a short row every month from May to July keeps them coming from late June until the first frosts.

Sowing indoors

Start French beans indoors if you want early pods or your garden is cold. Sow one bean per 8 cm pot or deep module, 4 cm deep, and keep them somewhere warm and bright. They come up within a week or two in warmth.

Don’t start too early. Plants that have to wait in pots for weeks get leggy and check badly when they’re finally planted out. In a cold spring, a late April sowing does better than a late March one.

Sowing outdoors

Bean seed rots in cold, wet soil. That’s the main reason outdoor sowings fail, so it’s worth waiting until the ground feels warm to your hand, usually from early May in a typical garden. A cloche or sheet of fleece over the row for a week beforehand warms the soil quicker.

1. Choose a sunny, sheltered spot with soil that has some compost dug in.
2. Sow beans 4 cm deep and 15 cm apart, in rows 45 cm apart. For blocks, 15 cm each way works well.
3. Sow a few extra at the end of the row to fill any gaps.
4. Water once after sowing, then hold off until the seedlings appear, so the seed doesn’t sit in soggy soil.

Outdoor sowing carries on until early August. The last sowings give a useful crop in September and October, after the first summer sowings have finished.

The dates here are for a typical lowland garden in England or Wales, with a last frost around 20 April and a first frost around the end of October. In Scotland, the north of England and frost pockets, sow outdoors from late May and finish by mid-July. In the south-west, near the coast and in cities, you can start a little earlier and sow later.

Dwarf or climbing

Dwarf French beans grow to about 45 cm and need no support, though a few twiggy sticks stop a heavy crop flopping. They’re ideal for raised beds and pots, and fit nine plants to a 30 cm square in square-foot gardening.

Climbing French beans grow up canes, netting or a wigwam to 2 metres or more. Grow them like runner beans, one plant per cane. They give more beans per square metre and are less fussy than runner beans about setting pods in hot weather.

Neighbours

French beans grow well alongside sweetcorn, cucumbers, potatoes, aubergines and celeriac. Keep them away from onions, garlic, shallots and leeks.

Picking

Pods are ready from late June to late October, depending on when you sowed. Pick them when they’re about pencil thick and snap cleanly, before the beans inside make bumps in the pod. Pick every few days. The more you pick, the more the plant flowers.

If you’d rather have dried beans for winter, leave the pods on the plant until they’re dry and papery, then shell them.

Common problems

Seeds rotting. Cold, wet soil. Sow later, or start in pots indoors.

Slugs. They take young seedlings overnight. Check after dark and plant out sturdy plants rather than tiny ones.

Few pods. Usually dry soil at flowering. Water deeply at the roots once flowers appear.

Blackfly. Clusters on the shoot tips. Rub them off or wash them away with a hose.

You can find every sowing window on the French bean page.