French beans, also known as green beans or common beans are one of the easiest crops to grow in your polytunnel. While French beans can be grown outside in most of the UK, they will enjoy the extra warmth when grown under cover and will reward gardeners with a bumper crop. Vertical gardening techniques can help you to grow French beans upwards into the little utilised space higher up in your tunnel and make the most of all the space you have. Frames made from branches or bamboo canes fixed to the crop bars in your polytunnel are a traditional solution. Wigwam style supports make sense where space is at a premium.
Sow one bean at the base of each cane or support branch. As the beans grow, gently tie the vines to the supports. Before you sow them, it is a good idea to prepare the area by adding some good quality compost or well-rotted manure. When exactly you will sow the French beans will depend on where you live but generally speaking, you should wait until after all risk of frost has passed where you live, as French beans are not hardy and love the heat. This means planting some time between April and June, depending on where you live in the UK. In more northerly areas, it may be a good idea to sow seeds in pots indoors and plant out into the polytunnel in June/July when the weather warms. This can also be a good idea in places where birds can pose a threat to young seedlings.
Water your beans well during the summer and lay a mulch of well-rotted organic matter or good quality compost at their base to conserve soil moisture. French beans, like other legumes, are nitrogen fixers and can help to provide nitrogen to other plants in your polytunnel or garden. There are a wide range of different varieties to choose from, some with beautiful pods that add visual interest as well as tasting delicious.
Begin to harvest your French beans when the pods are around 10cm long. You can tell that pods are ready because they will snap easily and yet the beans inside are not yet visible through the pod. By picking on a regular basis, you can prolong a crop and enjoy harvesting beans for several weeks. Feed with an organic liquid feed to boost the yield. French beans are usually eaten whole as pods before the beans inside are fully mature. However, it is possible to allow the beans to continue to maturity and to harvest the beans inside. These beans can then be frozen or dried for winter stews and casseroles. Choose your varieties carefully based on how you intend to eat the crops and you can enjoy many delicious meals with French beans throughout the year.
Sow under cover - March to June
Sow outdoors - April to June
Expected lifting time – May to October