Few summer vegetables are as prolific as French and runner beans, and, considering that they originated in a sub-tropical region of North, Central and South America, that is rather surprising. (Incidentally in Central America the tuberous runner bean root is boiled as a vegetable.) They were introduced into Europe in the early seventeenth century, the runner beans initially as a decorative plant. French beans have become the continental bean, and are considered a little foreign, suspect and quite tasteless in some UK circles. In contrast, across the water they consider runner beans to be a little foreign, suspect and quite tasteless. The two beans certainly have a different flavour. In my opinion the runner is more robust and I prefer its taste. (I wouldn't eat French beans if you paid me.) Incidentally, the temptation to eat beans raw at any time should be resisted. They contain toxins which, fortunately, are broken down by cooking. The odd one or two won't do any harm, but don't make a habit of it. Both French and runner beans have climbing and dwarf forms, with the climbers often listed as pole beans or stick beans. The flat, wide runner bean pods grow fast and furiously to lengths of over a foot long. Varieties differ, but pods toughen as they mature, so the earlier they are picked, the more tender they will be. The bumpiness of the pods is not necessarily a sign that they are getting tough, because the cavity for the developing bean seed develops well in advance of the bean. Regular picking is the best guarantee of a continuous heavy crop, as flower production slows once seeds start to develop in the pods. Plenty of moisture keeps plants succulent and pods tender. Runner beans hate cold situations and exposed, windswept sites (don't we all). If planted on such a site, growth will be slow and pollinating insects deterred. If your garden isn't naturally sheltered you can increase yields greatly by erecting some kind of wind-break.
A fatal mistake is to sow runner beans in cold soil. For fast germination, soil temperature needs to be at least 53°F (12°C), which means waiting until the end of May if you want to sow outdoors. Even a light frost will kill young plants, so premature sowing never pays. You could use a soil thermometer to check soil temperature, or you can simply feel it yourself. On the whole, if soil feels pleasant to touch, it is safe to go ahead and sow. The soil can be warmed up in advance by covering it with cloches or clear plastic film for a week or so before sowing. As runner bean seeds are very large, the easiest method of sowing is to make a hole with a dibber and drop the seed in so that it is covered by about 2 inches of soil. For an early start, sow seeds indoors, in a cool greenhouse for example, towards the end of April. Sow them in potting compost about 1½ inches deep, in modules, small pots, or seed boxes. Harden them off well before planting out at the end of May or early June, when they are about 3 inches high. They can be planted out a little earlier if protected with fleecy film.
Runner beans are excellent plants for decorative vegetable garden enthusiasts, too. The flowers are colourful over a long season, and are stunning when they grow so tall. Try using them as screens, or else encourage them to climb up arches, trellises and pergolas. You can even have a garden walkway covered by runner beans. On a lower level, dwarf varieties can be treated like bedding plants. They look quite at home in a flower bed, and will grow into evenly shaped bushes 12-18 inches high. The flowers top the bushes, adding a gorgeous splash of colour. Grow them in a group rather than rows for the best effect; the beans will develop quite happily even where crowded by other plants.
Runner beans do best in well drained, deep soils. Avoid soils that are very acid or alkaline, very light or heavily waterlogged. They have deep roots, and need a steady supply of moisture throughout their long growing period. This is the main reason for digging a lot of organic matter into the ground before planting. It is not normally necessary to apply any other fertilizer. Runner beans have root nodules enabling them to change nitrogen in the air into a valuable form of plant food.
Probably the best way of growing runner beans is to prepare a trench the previous autumn. For a double row of beans make it about 10 inches deep and up to 2 feet wide. Take out the top layer of soil, fork over the lower layer, and line the trench with well rotted straw, strawy manure, mushroom or garden compost or even layers of newspaper. Then replace the soil. Alternatively, you can use the trench as a compost bin throughout the winter, putting in any domestic waste that will rot. In early spring fill in the trench with soil and it will have time to settle before sowing or planting. If you can't make a trench, dig the ground thoroughly and work in as much organic matter as you can before sowing or planting.
Climbing runner beans need strong supports. They can grow up to 10 feet and are heavy when mature. The leading shoot will twist around wooden poles, up strings or wires or netting, (which should be 4 to 6 inch mesh to make picking easy). Young shoots may need tying in the early stages if the supporting surface is slippery. It is best to erect supports before sowing or planting. The crucial factor is stability: a guy rope at each end of a row may be necessary to give extra strength.
Finally, here are a few facts to help you decide which sort to grow. Dwarf forms mature earliest, but climbers crop for longer, eventually giving a higher overall yield. They do, however, require strong supports. French beans, which are self-pollinating, do better in high temperatures. Runner beans will grow in slightly cooler conditions than French beans, and may not be fertilised in very hot, dry summers for physiological reasons, or in very cold weather, which upsets the insects that pollinate them. Runner beans are perennials and although they die off in our cold climate, if the roots are lifted in autumn and stored in dry sand or soil in a frost free shed, they can be planted out the following year.
Happy gardening,
written by Bill Hutchings
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page last updated 1 APRIL 1999