I had planted a solid jungle of these (so thick at first that you couldn't even see the layer of sand I use to keep fungus gnats at bay). They're from 'Stonehead' cabbage that had gone to seed. My glossy kale/collards were in bloom at the same time and I was hoping to recover some hybrids among them. Well... sadly, "damping off" fungal disease ran rampant through the bunch and laid nearly all of them to waste. These are the only glossy ones that survived the onslaught.
This sort of challenge may explain [note to Joseph] why my Brassica lines might tend to have some extra robustness built in.