I had a batch of these (planted summer 2010) go to seed this summer and then regenerate again from the stumps so that they're tending towards perenniality. The first two pictures show two of those persistent ones gearing up to try making it through another winter. The harlequin bugs have been attacking the biggest one pretty severely. Maybe some of the smaller ones might be better to keep for seed for that reason. I also have some new plants coming along from a Spring sowing. They survived the summer drought while still just small seedlings. The third fourth and fifth pictures show some of these new seedlings. The third picture has a non-glossy (normal) seedling on the right so you can see the difference - glossy seedling is on the left with a few small non-glossy seedlings underneath. The deer have been munching the leaftips off. And you can see how the cabbageworms prefer the normal type. They'll crawl over and eat the glossy seedlings too, but I think the butterfly prefers laying eggs on normal type, so those will typically have much more damage. [I don't even spray Bt so these are completely unprotected] The last picture has an arrow pointing to an especially nicely purple-tinted seedling. The picture doesn't do it justice.
I'm hoping that the 'Stonehead' cabbage, 'Tuscan' kale and purple ornamental cabbage we just planted will make it through the winter so we can get these stirred into the genetic melting pot too!