My runner beans usually grow well. This year I did nothing different and the beans grew vigorously and had many flowers, but very few set. They were well watered and in a very warm position. What went wrong?
This year there have been many reports of lower than usual crops of runner beans and there could be several causes.
We have just endured the third very dry summer in a row and the water table has shrunk considerably. Irrigation needs to be increased to ensure healthy, sturdy plants and flowering. Often if the plant dries out during the flowering process or when very small beans have first formed, it’s common for them to fall.
Grow next season’s runner beans in a new site because where you’ve been growing them over the past few years may be depleted of key nutrients. Your new site should be sheltered, particularly from the wind, as the delicate flowers can be easily blown off plants before they mature into young beans. Soil should be free draining and well prepared with lots of added compost. When plants are a metre high, add mulch to retain soil moisture.
Try growing a different variety of runner bean such as Shiny Fardenlosa, and consider dwarf beans too, as they grow quickly and have good bean production.
It is generally understood that runner beans are self pollinating. However the activity of bees will enhance the crop so plant lavender, calendulas and marigolds to encourage pollinating insects.