Even though you may be noticing more of these hardy brassicas in restaurants and grocery stores these days, they're far from new. Kale in western Europe dates back to the Middle Ages, if not before, where it was bred to thrive in cold northern climates. Collards are traditional not only in the United States, but in Africa, Europe, and South America as well. Both are outstanding sources of Vitamin K and iron, among other nutrients. If harvested carefully, kale and collards keep producing long after other leaves leave the garden; after the first frost, they get sweeter!