We love them.
They’re easy to save seeds from. Just let one or two hulls/whole pods from each plant get dry on the plant. Pick those, shell them/etc and save for next year.
http://www.southernexposure.com/southern-pea-cowpea-growing-guide-ezp-53.html
“Seed Saving
Cowpea is self-pollinating and will rarely cross, although it can happen. Like all legumes, the flowers are visited by honeybees and bumblebees, but only the bumblebees are heavy enough to be effective pollinators on the short stigma flowers. On plants being saved for seed, allow the seeds to dry on the plant for as long as possible, gather and continue to dry indoors with good air circulation and then separate seeds from the chaff. Store seeds in a cool dry place and they will remain viable for 4-6 yr.”
From:
https://sowtrueseed.com/product/productmississippi-silver/
One thing I’d add is to dust the seeds with diatomaceous earth, DE, (we get ours from the local co-op) when they’re dry before you store them. This will prevent any bean weevils from making their home in your seed stash.
I love harvesting seeds. Don’t ask me why, but it is one of my favorite parts of gardening.
I have some raised beds that I have set aside just to grow plants to get seeds from. A couple of them are plants that will only give me seeds the second year. I’ve only had luck so far with carrots and onions. The Swiss chard and beets haven’t made it through the second year – yet.
Good ideas. When I get to my last crop, this I shall remember.