French & Runner Beans

It is important to grow some bean plants specifically for seed, rather than simply collecting the left-over pods at the end of the season. The plants should be good strong specimens, and any that are less healthy looking or not true to type for the variety should not be used for seed production.

French beans are self-pollinating, mostly before the flowers open. Despite this, they can be crossed by insects with other varieties nearby. The extent of crossing varies by area. If you are just saving seed for your own use, grow your seed crop of French beans at least 6 feet away from any other variety (12 feet if possible), and you are unlikely to have a significant problem with crossing in the UK.

Runner bean flowers need to be 'tripped' by wind or insects before the beans set, and are much more likely to cross with other varieties grown nearby than French dwarf beans. Ideally, to be sure that no crossing takes place, seed crops of runner bean should be at least 1/2 a mile away from any other varieties of runner bean. Bear in mind, though, that buildings, trees, and other barriers will limit insect flight patterns, and if you are gardening in a town or built up area, you are likely to have relatively little problems with crossing unless your immediate neighbours are also growing runner beans. If they are - or on an open site such as an allotment - your only answer may be to try to persuade your neighbours to grow the same type of runner.

To collect the seeds, allow the pods to mature fully on the plant until they start to turn yellow and dry out. In wet weather, collect the pods individually as they get to this stage. Then spread out somewhere out of the rain with a good airflow until the pods are fully dry and brittle. Once they are dry, shell out the beans and dry further out of the pods. The beans should be dry enough that they break when you bite on them, rather than leaving a dent. Store in an airtight container. If they are well dried, and stored in a cool dark place, the beans will last around 3 years.

If you have problems with weevils eating your seeds, put the sealed container in the freezer for a week immediately after drying the beans; this will kill any insect eggs before they hatch. When you take them out, let the container come up to room temperature before opening it, otherwise the beans will absorb moisture from the air. More information on seed drying can be found under our section ‘Seed Cleaning and Drying’ on our website.