As predictable as rain on a Bank Holiday, my postbag (well inbox) is starting to fill with questions about runner beans. I can usually predict questions by the time of year just as when I used to visit flower shows with The Garden Roadshow, we could often predict the questions, especially the last question of each session. If we had one minute left to squeeze in one quick question nine times out of ten it would be ‘how do you get rid of mare’s tail’ and if not it would be ‘I have a garden in the south of France and there is something eating the leaves of my orange tree’.
But August means runner beans. There are lots of questions for two reasons; because they are very popular, in the UK and because they cause a lot of worries. They do not crop as regularly as French beans and they are more fiddly to prepare, but nothing compares with fresh runners.
The problem is usually not in growing them but in getting the beans to set. It has been a problem for decades. The flowers open, they drop off and…nothing – just a stalk. So how can we avoid this?
Firstly, runner beans prefer a soil that is not too acid and it is a good idea to lime the soil before a bean crop. Some gardeners spray the plants with lime in water but this is not necessary. Dryness is an issue so keeping plants well watered and making sure there is lots of organic matter is good too. Some gardeners like to spray the plants with water in the evening and others spray with sugar water to encourage bees – though it is more likely to attract wasps. Others think that watering with cold water at night makes the flowers drop off.
In some gardens sparrows will attack the flowers. This is to get to the nectar. If you grow pink or white-flowered beans you can avoid this. Runner bean flowers are not easily pollinated by bees and the bees chew through the back of the flowers to get to the nectar but this is not a real issue.
Part of the problem is that we sow the seeds early and put out plants at the end of May to try to get the earliest beans we can. The fact is that although runner beans are native to Central America, they come from high elevations and the pods will not set when night temperatures are high. That is why the first flowers on the plants often fail to set. As temperatures drop, runner beans set easily. While there may be few beans in August you always get loads in September.
This year, because everything went wrong with the veg plants this spring, I had to sow the runners direct in the soil under the strings and they are doing really well. The first flowers are opening and they are already setting pods, because it is not excessively warm now. I have not watered them at all, though the soil is quite dry. But the soil is mulched with manure to retain some moisture.