Runner beans are a productive crop that can offer great value for space in your polytunnel. These vining beans can also help you to make the most of the vertical space in your tunnel. While you can also grow runner beans outside in most of the UK, a polytunnel can help keep your crop safe and healthy and allow you to grow beans to maturity for storage or to plant the following year. Once only viewed as an ornamental, these plants have attractive flowers before producing long edible green beans followed by the beans within the pods when mature.
Runner beans can be very easy to grow. They can be sown directly into your polytunnel between May and July, or sown indoors and then planted out in the polytunnel between late May and early June when the weather has warmed in your area. Before sowing, you will need to prepare the area where your runner beans are to grow. Runner beans are hungry plants and are often placed on a 'bean trench' which has been prepared over the previous few months. The trench should be filled with kitchen scraps, compost and organic matter, which will provide nutrition to the growing plants. Mulching plants with good quality organic compost is also a good idea.
When preparing a site for your runner beans you will also need to consider a structure for your beans to grow up. Bamboo canes are often used, sometimes in a wigwam structure, which can be a good choice for small spaces. You may also want to consider a larger vertical structure affixed to the crop bars in your polytunnel.
Sow beans two to each support cane, thinning to one per cane, or plant out the plants sown earlier indoors one plant per cane. Runner beans should be no closer than 15cm apart.
When the plants have reached the top of their supports, pinch out the growing tips to stop the plants from becoming top heavy and to make sure you can reach the crop when harvesting. Remember to water your plants well, as runner beans require a lot of water to produce a good quality crop. Pay especial attention to watering once the flowers have formed.
As a nitrogen-fixer, runner beans can be a beneficial companion plant for a range of other plants. Consider sowing runner beans in a mixed, polyculture bed with other summer crops such as squash and sweetcorn.
Runner beans should be harvested when the pods are less than full length and have not gone stringy. They will usually be around 10-15cm in length at this stage. Pick the pods regularly to ensure a continued supply, though you can leave some to mature fully and form beans that can be stored for winter use in the kitchen or for sowing the following year.
