Upright herbaceous plant up to 1.7 m high, glabrous and glaucous. Alternate, oblong to obovate leaves up to 35 cm, tripinnate with the last filiform segments; petiole pods 1-3 cm long. Inflorescences with terminal and lateral umbels; numerous flowers with yellow petals. Fruit ovate-elliptic, glabrous, up to 4 mm long, compressed dorsally, narrowly winged ribs, the 2 lateral ones are broader.

This species is often confused with Foeniculum vulgare, which has a longer petiole pod and all the ribs of the fruit are the same.

Annual plant, very aromatic, erect, up to 2 m in height, covered with long hairs. Alternate or opposite bipinnatifid leaves, 3 to 10 cm in length. Greenish male flowers in long terminal buds, female flowers in leaf axils. Fruit in ovoid, angular and thorny achenes, 3 to 4 mm in length.