Harvest constantly only really applies to harvest as snap beans. Once the beans get full grown as either green shellies or dry as in seed aor dry beans, the plant has done its thing. Especially true of bush beans. Dry means just that the pod will be dry. Leathery the pod will have changed color, beans will be full, and the pod will be thin and a texture reminding one of thin leather. At that point the the beans will contain a lot moisture, be considerably larger than their dry state, and be easy to shell for green shellies. For snap beans the pods are harvested before the beans form. You eat pods not beans.

For seeds that are rare, or that have either suspected or demonstrated poor germination, the planting method I recommend is to start them indoors in pots. Use a sterile soil-less medium, and boiled water, to minimize the chance of rotting. The object is not to start them early, but to minimize losses & produce a uniform stand. The use of transplants also protects from early losses due to insects, birds, or animals. So I'm in agreement with Tcstoehr's advice... but plant them indoors at the same time you would normally plant them outside, so you can transplant any which come up. You don't need to get a good germination rate to preserve a variety; even a single bean plant will provide quite a bit of seed. Several of the heirloom bean varieties I grow now were initially rescued from a single surviving plant. Last year, only 1 out of 50 seeds of the bush bean "Atlas" germinated. That single plant produced about 80 seeds, which I hope to multiply to a larger quantity this year.

How many plants you need to save depends upon several factors... the variety, soil fertility, hours of full sun per day, and plant spacing are some of the most important. Spaced 6-12" apart, in full sun, you can expect 50-100 seeds per plant from most varieties; in fertile soil, better than that. Subtract from that if plants are shaded or planted more closely, and account for the fact that bad weather can cause losses if the dry & near-dry beans sprout or mold. 5-6 plants of each, properly spaced, should produce the amount of seed you intend to save.

Annette, thank you for your informative post. That's much like what I found out when I began looking for seed to replace what I ran out of due to 3 successive years of failed crops due to weather and rabbits nipping the plants off at just above ground level. The beans that I originally had were some that I got in a seed trade on GW, but I can't remember who it was that sent them to me. It's been a long time ago. They were kidney shaped. My thinking at this point is that I got someone's "landrace" bean. Last year I grew a bean marketed by Terroir Seed as "Lazy Wife" and it was disappointing. It was a kidney-shaped white bean. This year's trial was "Lazy Housewife" from Shumway's. It was more of an egg-shaped white bean. George, thank you for that link. The beans I planted this year, when in the pods, do look like the ones in the picture on Sustainable Mountain Agriculture except maybe a little longer and wider, and it seems like they stay flat forEVER. By the time they look like the ones in the picture they are too fibrous to eat as snap beans, and yes, I have harvested the seeds, such as they are, and will be cooking them today before they have a chance to dry out, as many of them are small and will shrivel if allowed to dry. I will freeze them in the broth and add to vegetable soup this winter. They were delicious when picked young. But whatever variety I had at first was quick to produce seed. Considering that I have to compete with the grasshoppers every day that they hang on the trellis, being able to get seed within a shorter period of time is key. I've tried growing fava beans in the spring and the grasshoppers are not at full population yet. Even so, I can never get a crop due to something drilling through the pod into the bean. I've given up on fava beans and to this day have never tasted them so I don't even know if I would like them. I am going to try Lone Jack's Provider bush beans next year, though I might try another variety of Lazy Wife/Housewife if I can lay my hands on something else to try. I love home-canned green beans and have really missed not having any in the pantry. Maybe I can get away with growing both kinds at the same time, as one is bush and the other pole, and I will not plant them both in the same bed. A side note: when I was a kid, my mother believed "green bean juice" was ever as much restorative as was chicken soup. When stomach flu or some other such upsetting virus would make its rounds in my school till it found me, it would always be the first thing she offered when I thought it was possible to hold something down, lightly salted, and if that was successful, the next round was "garnished" with torn pieces of homemade bread, lightly buttered. If I could keep that down, I was pretty much well. :~} This is actually one of the main reasons why I prefer to grow my own seed. The other reason being economy. I would not be growing a garden at all, considering how hard it is to get a decent crop, if economy was not one of the driving forces. That and knowing that no chemicals have been applied. We are expecting our first freeze early on Tuesday morning. Oh, Annette, I just got an email telling me you have posted again, I will post this and then read your post so as not to lose what I've written here. Been there, done that. --ilene