In the list of cultivars of dried beans at North Carolina State U., I saw listed a pinto bean cultivar for the Pacific Northwest with a note that it had some runner bean parentage. I was very surprised, because I didn't think common beans and runner beans crossed.

If this was a natural cross, I wonder if the reason people have trouble keeping the pole bean variety "Jeminez" true to type is that it has some runner parentage, which could change the blossom structure to encourage more cross-pollination?

Additions:
-Adzuki
-Winged bean (same climate as hyacinth)
-Tepary bean
-Favas
-Fenugreek
-Black gram (will not cross with green gram)
-Lentil
-Peas (as in "English" peas)

So while all of the legumes listed so far may not be appropriate for every location & climate, any gardener could easily grow one each of several, and save pure seed.

As to inter-species crosses... Several years ago, I requested a runner bean from Seed Savers Exchange. The seeds, upon examination, had some purple coloration, and appeared to be small runner beans.

When I planted them, however, the cotyledons emerged from the soil - and runner beans are, by accepted definition, hypogeal. It appeared to be a cross between P. coccineus (runner bean) and P. vulgaris (common bean). Since I wasn't sure how to isolate it from my other beans (too late to change plans), I chose not to grow it & destroyed the seedlings. I still have seed remaining, which I intend to plant this year... I'm very curious what the blossoms will look like.

Curious, I scanned through the USDA's database of runner beans, looking for something similar. I found one that appeared to be nearly identical to mine - and was epigeal. And much to my surprise, I also found other epigeal runner beans, all of which appear to be possible inter-species crosses within the Phaseolus genus. I intend to write the curator, to request her opinion on this... I hope they respond.

I remember having a similar discussion some time back, and a GW member came forth, claiming that they had a cross occur in their garden between runners & common beans. I believe it was a European member. While inter-species crosses do occur, they are statistically very rare; very few of those are viable, and even fewer are able to produce seed. When it does happen, such a cross represents an opportunity to breed a new variety.

This is invaluable info for those of us with small gardens. I try growing some of each one but I'm still struggling with when to plant and where to buy seeds. I haven't a place yet that sells all varieties.

If you do a bit of digging on the net, you will find that common pole beans and runner beans can be crossed under lab conditions. They do not normally cross in the garden.

The original reason runner beans were crossed into pinto beans was to bring in some disease tolerance.

DarJones