There are a number of reasons that leaves on runner beans dry up and curl. The most likely reason is lack of water. Runner beans need plenty of water to assist with their growth. Another possible reason is that they are coming to the end of the season. Runner beans grow best when planted the week before the last frost of the year is forecast. Plastic can protect them if a late frost is forecast, as can growing them inside on a windowsill to protect them from the elements. They can be moved outside and replanted once the weather has warmed up a little. When planting runner beans, it is essential to ensure that the soil is not too rich in nitrogen as the beans can extract nitrogen from the air and fix it to nodules on the roots. The soil should be prepared in early spring, and should be able to hold lots of water to aid growing. They are best planted in a position with full sun and wind should be avoided. This is another reason that the leaves can curl up and dry. Windburn will cause the plant to shrivel. Be careful when planting other vegetables alongside runner beans as they create a large area of shade that is not beneficial to many vegetables. It is common for some runner bean varieties to grow as high as 6 foot tall, and this will see them dwarf other vegetables and plants. When picking runner beans look out for the crisp, tender ones that are firm to touch. Cut off the tops and tails and run a knife right through the bean to string it. They should then be sliced horizontally and should be used as soon as possible after picking.
