Today the runner bean (Phaseolus coccineus) is one of our best-loved and most widely grown vegetables, but it has also long been grown as an ornamental climber in many countries. Its other popular names include ‘scarlet runner’ and ‘Dutch case-knife bean’. It has been grown for food for more than 2,000 years and originated in the tropical uplands of Central America and is believed to have been brought to the British Isles by John Tradescant, who was gardener to Charles I.
Runner beans do best in a warm spot, which also encourages pollinating insects. Do not grow them in the same position year after year, as this is likely to cause a build-up of root-rotting diseases. They enjoy very rich, well-drained soil and a sheltered sunny position. They don’t like heavy clay soil and need a neutral pH to thrive. In the autumn, dig-in as much compost or well-rotted manure (such as Orgro) as possible and some lime, if your soil is very acidic.
A few weeks before sowing, add a good scattering of general purpose fertiliser to the soil and set-up 2.4m/8ft tall canes in rows or wigwams. If conditions are favourable then you can sow direct into the soil from mid-May, however it’s best to wait until the risk of frost has passed. Early sowings can be done in Rootrainers, kept undercover and planted out from late-May (after hardening off). Sow seed outdoors to a depth of 5cm/2in. and space them at 20cm/8in. intervals in rows 45cm/1½ft. apart allowing 2 seeds per cane. Tie the young plants loosely to the canes and protect them from slugs. They’ll quickly climb naturally and will need no other support. Water plants liberally and frequently, especially during dry spells and harvest the pods when they’re about 15 to 20cm/6 - 7in long. Picking the beans regularly should give you a continuous supply for over 2 months.