I am trying to grow a seed crop for distribution to other seed savers of 3 varieties of long beans (Vigna unguiculata cultigroup Sesquipedalis). Many pix posted in Garden Galleries > Great Vegetables. Thus far I have successfully saved seeds from only one variety.. details below the questions. Hummingbirds still happily frequenting them wherever they are planted. They will leave first week October to migrate south again...

1) What is the coldest night temperatures at which these plants will mature quality seeds?

We are about 6 weeks yet from frost, but we are now only 2 weeks from 50 degree nights, and I know these are considered tropical plants.

2) How many pods can I leave to ripen seeds and still get a vegetable harvest from these plants?

I have an eager consumer for the Anna's Taiwan Green... I barter them for dinners in my friend's restaurant... This bean failed for 2 other growers (both Taiwan-born), so there is exceptional interest in my producing a crop of this favorite vegetable.

Currently I am hiding ripening pods behind the foliage where they do not show when I send my friend internet photos of the wall of her beans....

More discussion:

Thus far I have successfully saved seeds from only one variety.... Yardlong, Purple Pod. Most of these seeds I got from first bloom before the extreme heat and drought, but I am also bagging blossoms to ensure that all plants are well represented in my seed saving.

During our month of 100+ degree heat, both purple varieties were blooming and setting pods but most of them were totally empty or had only a few seeds (2-3).

The variety from the Philippines, considered day-length sensitive, is now blooming abundantly as the temperatures have dropped to 65 nites / 90 days and we near the equinox. The earlier bloom... apparently stress induced... succeeded mostly in causing me cross-pollination problems.

I have hummingbird cross-pollination problems, and now a few bumblebees as well, so I am bagging scores of blossoms daily against these bigger nectar feeders.

Another variety, Anna's Taiwan Green, was planted later and is just now blooming. I consider it isolation planted, as it is 150 yards from the purple varieties, separated by buildings, low trees, and a bamboo grove... and theoretically in a different hummingbird territory. The hummingbirds begin at dawn in this area with blossoms of okra, longbeans, and bitter melon, plus still some trumpet vine in uncleared areas. They got lucky...

Those visiting the purple pod beans are adding them to a floral menu of maypops (Passiflora incarnata), a few wild morning glories, and blooms of cherry tomatoes and lima beans.

Thanks for your assistance. I have posted... Under Forum "Beans, Peas, and Legumes"... a further discussion of problems growing these beans this year in Arkansas. They have failed for 2 Taiwan-born gardeners... and my own beginner's experience suggests they may have somewhat limited soil fertility preferences, plus I am unsure of water requirements.