Seed Saving from French Beans
French beans are self-pollinating, mostly pollinating before the flowers open, but they can be crossed by insects with other varieties of French bean growing nearby.
The extent of crossing varies by area. If you are just saving seed for your own use, grow your seed crop of beans at leastsix feet away from any other variety (12 feet if possible), and you are unlikely to have a significant problem with crossing.
To collect the seeds, allow the pods to mature fully on the plant until they start to 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 three years.