Broccoli has large (10 to 20 cm) green flower heads, arranged in a tree-like structure on branches sprouting from a thick, edible stalk. The mass of flower heads is surrounded by leaves.
Broccoli is harvested when the flower buds are closed and compact with no yellowing buds or flowers evident. Stalks and stem leaves should be tender yet firm. Avoid any with yellowing flowerets and thick, woody stems. Heads are removed with about 10-15cm of stem attached.