Cabbage, broccoli, cauliflower, kohlrabi and Brussels sprout are all of the same species. Brassica oleracea is weirdly diverse, and also includes kale and collard. All varieties are collectively the cole crops. They are cool season vegetables that grow from autumn until spring. Most are biennials that grow as annuals. Some kales and collards are perennial.

Collard does not form heads like cabbage does. It instead grows loosely on stout stalks. Most are only about two feet high. A few perennial types can grow six feet high, and can grow from cuttings. All other types grow from seed or cell pack seedlings. More varieties are available as seed than as seedlings. Online markets offer more than nurseries stock.

Although perennial collards provide greens all year, they are better during cool weather. Also, collard greens are best while young and tender, before they mature too completely. They are easy to collect from the bottoms of the foliar rosettes, upward towards the tops. They need, however, to retain enough leaves to continue growing through their season.