Actually more closely related to the turnip (Brassica rapa var. rapa) then broccoli, Rapini is likely the semi-domesticated descent of a wild herb originating either in China or the Mediterranean region.
Rapini is a good source of vitamins A, C, and K, as well as potassium, calcium, and iron. The leaves, stems, buds, and flowers are edible. Photos of the flowers and buds below.