This is going to be a longish story; I tend to do that. You have been warned. On my first pilgramage to the Seed Saver's Exchange summer campout, I met Dennis, a fellow gardener and heirloom veggie nut. He had been injured at work, but was still getting around pretty well...one obsession of his was turnip greens. Dennis trialed many varieties in his quest, finally settling on a Czech variety: "Horpaczi Lila," which he got from the East German seed bank! Fast forward some years. Dennis is now less mobile, but I have visited him most years at his apartment north of Chicago. At one point he tells me the turnip story on the phone, and says he has some pretty old seed he'd like to have grown out (hint, hint), so he mails me part of his at least 10-year old stock, which I plant that spring in the greenhouse. Yield: about a dozen plants, and a teaspoon of seed. Next spring, to the garden, harvesting a couple dozen roots. The next spring, about a pound of seed! I still have some of that seed, germinating about 25% indoors, and I'm not getting any younger. Sooo.... if anyone would like to grow this out (you can steal some of the first-year leaves to do your own taste test) drop me an email with snail address. No obligation except to do your best to "pay it forward" and raise some more seeds to keep this old-timer going.
Cheers!