Fennel (Foeniculum vulgare) is the most important species in the genus Foeniculum (treated as the sole species by many botanists), and is native to southern Europe (especially by the Mediterranean) and southwestern Asia. It is a member of the Apiaceae (formerly the Umbelliferae).
It is a highly aromatic perennial herb, erect, glaucous green, and grows to 2 m tall. The leaves grow up to 40 cm long; they are finely dissected, with the ultimate segments filiform, about 0.5 mm wide. The flowers are produced in terminal compound umbels 5—15 cm wide, each umbel section with 20—50 tiny yellow flowers on short pedicels. The fruit is a dry seed from 4—9 mm long, half as wide or less, and grooved.
Fennel is used as a food plant by the larvae of some Lepidoptera species including the Mouse Moth and the Anise Swallowtail. Fennel is widely cultivated both in its native range and elsewhere of for its edible, strongly flavoured leaves and seeds. The flavour is similar to that of anise and star anise, though usually not so strong. The Florence fennel (F. vulgare Azoricum Group) is a selection with inflated leaf bases which form a sort of bulb. It comes mainly from India and Egypt and it has a mild anise-like flavour, but is more aromatic and sweeter. Its flavour comes from anethole, an aromatic compound also found in anise and star anise. Florence fennel is smaller than the wild type and has inflated leaf bases which are eaten as a vegetable, both raw and cooked. There are several cultivars of Florence fennel, which is also known by several other names, notably the Italian name finocchio. In United States supermarkets, it is often mislabeled as "anise". Both the foliage and seeds of the fennel plant have secure places in the culinary traditions of the world. Dried fennel seed is an aromatic, anise-flavoured spice; brown or green in colour, they slowly turn a dull grey as the seed ages (for cooking, green seeds are optimal). Fennel seeds are sometimes confused with aniseed, which is very similar in taste and appearance, though smaller. Indians often chew fennel seed (or saunf) as a mouth-freshener. Fennel is also used as a flavouring in some natural toothpastes. Some people employ it as a diuretic, while others use it to improve the milk supply of breastfeeding mothers.
Many cultures in the Indian subcontinent and the Middle East incorporate fennel seed into their culinary traditions. Many egg, fish, and other dishes employ fresh or dried fennel leaves. Florence fennel is a key ingredient in some Italian and German salads, often tossed with chicory and avocado. One may also blanch and/or marinate the leaves, or cook them in risotto. In all cases, the leaves lend their characteristically mild, anise-like flavour. Fennel essential oil is used in soaps, and some perfumes.