When to plant French beans?

When, by region

April, the 10–12 °C threshold, the close at the end of July, and early August only as a catch crop, are from ARPA Umbria's bean sheet, written for growing the crop and multiplying seed. December to March, on the same sheet, is sowing in a greenhouse or tunnel, for an early crop eaten fresh. Cornell writes that below 60 °F (about 16 °C) germination is poor, and that above 32 °C (90 °F) pod set is often poor. The RHS, in a cool climate, sows outdoors in late spring or early summer, once frost has passed and the soil is warming. Months for the other crops are in the planting calendar.

Direct sowing, not a long spell indoors

This page is the common bean, dwarf or climbing, picked while the pod is still tender. Broad beans, sown in autumn in mild areas, are a different crop: timing and depth are in peas and broad beans.

Cornell advises against starting them indoors, because beans resent transplanting, and against soaking the seed: it damages it. The RHS, for an earlier crop, still sows in pots from late April in a cool climate, one seed per pot, 5 cm (2 in) deep, and moves plants outside once frost has passed, usually late May or early June there. In a home garden the safer path is direct sowing, once frost has passed and the soil is warm. If you do start a pot, one seed, and the root ball stays intact. The pot method is in the homemade seedbed.

Depth, dwarf, climbing

The RHS sows 5 cm (2 in) deep. Dwarf plants go 15 cm (6 in) apart, in blocks or double rows, so they hold each other up. Repeat the sowing from late spring to mid-summer. Climbing beans: one or two seeds at the base of each cane, then keep the stronger plant. Canes about 2.5 m (8 ft) tall go 15 cm apart in the row, in rows at least 45 cm (18 in) apart, tied at the top, and they go in before you sow. A wigwam of four or five canes, still 15 cm apart at the base, works in a large pot too.

The Umbria sheet, in a field, keeps dwarf plants tighter: a seed every 5–6 cm, in rows 60–70 cm apart. Climbing rows are 100–120 cm apart. Those are field distances, not balcony ones. In a home garden the RHS 15 cm lets air through. In a pot, dwarf beans are among the crops the RHS lists for containers: see the container garden.

Water, rotation, heat

The peak demand for water, ARPA Umbria writes, is at flowering. Overhead watering is not advised: too much on the leaves encourages fungal and bacterial disease. Water the soil, in the morning. How much is in watering, and the hardware is in drip irrigation. Straw around the stems, as the sheet suggests, holds moisture and weeds down: materials and depth are in mulching.

Beans are legumes and do not need much nitrogen. At the end of the crop, cut them at the base and leave the roots. ARPA Umbria asks you not to repeat them straight away, to wait two or three years, and not to follow them with other legumes. Cornell gives a three-year rotation. In a home garden, keep the three years.

Pick in several passes, while the pod is still tender. Leave it to swell seed, and the plant stops making new pods. Above 32 °C, pod set is often poor: in the south, in the hottest weeks, wait for a cooler spell rather than sowing into it.