Fennel (Foeniculum vulgare) is a plant species in the genus Foeniculum (treated as the sole species in the genus by most botanists). It is a member of the family Apiaceae (formerly the Umbelliferae).Fennel (Foeniculum vulgare) is a plant species in the genus Foeniculum (treated as the sole species in the genus by most botanists). It is a member of the family Apiaceae (formerly the Umbelliferae). It is a hardy, perennial, umbelliferous herb, with yellow flowers and feathery leaves. It is indigenous to the shores of the Mediterranean, but has become widely naturalised in many parts of the world, especially on dry soils near the sea-coast and on riverbanks. Fennel is used as a food plant by the larvae of some Lepidoptera species including the mouse moth and the anise swallowtail.Fennel is used as a food plant by the larvae of some Lepidoptera species including the mouse moth and the anise swallowtail.Fennel is used as a food plant by the larvae of some Lepidoptera species including the mouse moth and the anise swallowtail.