Join the green party: How to grow French beans

French beans are not really French. Like runner beans, they are New World creatures, brought back by the Spanish conquistadores. In England, they were an instant hit. The 16th-century herbalist John Gerard ate them "boiled together before they be ripe, and buttered". He thought them "exceeding delicate meat", and appreciated the fact that they "do not engender wind as the other pulses do".

When I first started to grow them, French beans meant bush beans, not climbing ones, but if you are short of space, the climbing types take up less room and crop over a longer period. This year I'm growing the climbing purple-podded 'Blauhilde' (Thompson & Morgan £2.29) mixed with sweet peas on hazel wigwams about eight feet tall.

For speed in cropping though, the dwarf bush beans are better. Depending on the weather, you can expect to start picking 60-70 days after you've sown seed. By nature, French beans are fast growing annuals but they hate cold, dank ground. If you sow too soon, seed may rot. For early crops, it's better to start seed off indoors or in a greenhouse. You can sow in deep boxes, but I prefer to use individual 7cm (3in) pots. This way, when the beans are planted out, there's less disturbance to the roots. For outdoor sowing, the soil temperature needs to be a comfortable 13C (56F). In our part of the country (Dorset), we've got to that breakthrough point. In gardens further north, the soil may take longer to warm up in spring.

Compact bush varieties grow very successfully in big pots or grow bags. Spread the crop by sowing a new pot (or a row) every three weeks between now and midsummer. If you are sowing in open ground, set the seed 3cm (1.5in) deep, in staggered rows, so that the plants grow about 23cm (9in) apart in the rows. In a pot or grow bag, you can sow more closely, but you will need to feed and water well. I use Tomorite for pot crops. It's as good on beans as it is on tomatoes. Seed should germinate in 1-2 weeks. If it doesn't, investigate. Mice may have eaten it. This is less likely to happen if you sow first in pots, then transplant. But the disadvantage here is that plants sulk for a bit, while they adjust to their less cosy surroundings. Water transplants as soon as you have settled them in.

French beans like rich, light soil, either neutral or slightly acid. They do best in a sheltered position. In a windy site, they may blow over, especially if they are bearing a heavy crop. Some gardeners tie their bean plants to short stakes. Some earth up plants. Both strategies are effective, if you have time to carry them out.

Generally, once they have germinated, French beans don't need much watering. The most critical time is when the flowers begin to open and the pods begin to swell. If they are thirsty at these points in their life cycle, flowers and pods just drop off. For the juiciest beans and the biggest crops, you need to pick regularly. Towards the end of the season, I let the pods develop because then you can shell them and gather flageolet beans to eat fresh. If you leave them even longer, the beans mature into haricots which you can store for winter.

By this time, in early autumn, the safest way to gather haricots is to pull up the whole plant and let the beanpods dry under cover in a shed or greenhouse. When they are really crisp and beginning to split, you can shell them. I let the beans dry out in a single layer on a tray before packing them into jars.

The French beans of my childhood turned stringy very quickly if you left them too long before picking. Modern breeding has eliminated stringiness and introduced more rounded, pencil-shaped pods, as distinct from the original, flatter varieties. And they come now in a wonderful array of colours: purple, like my 'Blauhilde', cream as in 'Sonesta' and the superbly flavoured 'Golddukat', as well as wonderfully speckled and spotted varieties such as 'Merveille de Piemonte' which has cream pods flecked with purple. 'Borlotto di Fuoco', the original Tongues of Fire bean, has the same pale pods, dramatically splashed with red. Although we think of it as an Italian bean, it may have originally come from Tierra del Fuego.

'Sonesta' (Unwins £2.99) grows fast, is only 35cm tall and spreads its harvest over a longer period than, say, 'Purple Teepee', (though not so long as a climbing French bean). It has a distinctive waxy flavour and the beans are quick to pick because you can see them more easily than green ones. Unsurprisingly, it kept its Award of Garden Merit when it was grown in the Royal Horticultural Society's recent trials of dwarf French beans.

For this most recent trial, 55 varieties were sown in the trials field at Wisley in late spring and assessed in August. The judging panel were interested in taste, of course, but also considered colour, tenderness, resistance to disease and speed of growth. The trials team grew 50 plants of each variety and gathered, on average, about 2.5kg (five and a half pounds) of beans from each block of plants. 'Maxi' (Marshalls £2.25) is another old AGM winner, and bore the heaviest crops, more than 4kg.

Purple-podded beans such as 'Purple Teepee' look wonderfully lustrous when you pick them, but unfortunately the gorgeous colour turns to green when you cook them. Despite this, 'Purple Teepee' (Suffolk Herbs £1.50) is productive and quick to mature. The harvest is shorter than with 'Sonesta', but I think the flavour of the purple varieties is unparalleled. Try them all. Between now and early July, there's time to start off a whole sequence of crops.

French beans: best of the bunch

Look for other AGM award-winning French beans such as:

'Annabel': Dark-green pods on a compact plant, fast and early.

'Boston': Glossy, bright-green pods of excellent flavour.

'Delinel': Flattish pods on a favourite old variety. Marshalls can despatch 12 plants (£6.95) in late May for picking in July & August.

'Golddukat': Rich golden-cream pods, with a distinctive flavour. Marshalls can despatch 12 plants (£6.95) in late May for picking in July & August.

'Safari': Crops well with dark-green pods even in a duff summer.

'Scuba': Heavy yielding variety with short, fat, fleshy pods.

Thompson & Morgan 0844 573 1818, thompson-morgan.com; Unwins 01480 443395, unwins.co.uk; Marshalls 01480 443390, marshalls-seeds.co.uk; Suffolk Herbs 01376 572456, suffolkherbs.com