By Harold McGee
Bulb or Florence or finocchio fennel is a vegetable variety (var. azoricum) of Foeniculum vulgare, the plant that produces fennel seeds. Its enlarged leaf-stalk bases form a tight, bulb-like cluster. (The rest of the leaf stalk, the equivalent of celery stalk, remains tough and fibrous.) Fennel has a strong anise aroma thanks to the same chemical (anethole) that flavors anise seeds and star anise, and this makes fennel a more dominating, less versatile ingredient than celery and carrots. It also has a distinct citrus note (from the terpene limonene) that’s especially prominent in the sparse foliage. Fennel is eaten both raw, thinly sliced and crunchy, and cooked, often braised or in a gratin.