Collard greens

Collard is a group of loose-leafed cultivars of Brassica oleracea, the same species as many common vegetables including cabbage and broccoli. Part of the Acephala cultivar group, it is also classified as the variety B. oleracea var. viridis. The plants are grown as a food crop for their large, dark-green, edible leaves, which are cooked and eaten as vegetables. Collard greens have been cultivated as food since classical antiquity. The name "collard" comes from the Greek word “kolaro”. The term colewort is a medieval term for non-heading brassica crops.

Source: Wikipedia