Gardeners have been debating for years about whether to spray runner beans with water to help them fertilise. A fine row of flowering plants without a bean in sight can be very frustrating.
The Royal Horticultural Society advises against spraying runner beans, saying there is no evidence it helps, and instead provides lots of tips about moist soil conditions and mulching. On gardeners’ forums, however, there is a lot of support for spraying simply because it seems to work.
Trials in my own garden in Bedfordshire over a number of seasons have led to the conclusion that in dry conditions, like those this summer, there are no beans at all without spraying, but a good late July crop is obtained if sprayed in early morning or late evening.
The clue to what works is probably in the plant’s origins in high altitude areas in Central America where locals first cultivated runner beans. The plant performs best above 2,000 metres when the nights are long and cool. This is probably why runner beans crop most heavily in Britain in September, when the weather conditions are closest to the plant’s origins in the mountains of Mexico. Perhaps we should also remember that runner beans were first introduced into Britain because of their red flowers and are still grown mainly as an ornamental plant in many countries.
• This article was amended on 22 July 2022 to refer to the fertilisation, rather than the germination, of runner beans.
