Apium graveolens is a plant species in the family Apiaceae commonly known as celery (var. dulce) or celeriac (var. rapaceum), depending on whether the petioles (stalks) or roots are eaten: celery refers to the former and celeriac to the latter. Apium graveolens grows to 1 m tall. The leaves are pinnate to bipinnate leaves with rhombic leaflets 3–6 cm long and 2–4 cm broad. The flowers are creamy-white, 2–3 mm diameter, produced in dense compound umbels. The seeds are broad ovoid to globose, 1.5–2 mm long and wide.
The effect of photoperiod on elongation of the flower stalk in celeriac (Apiumgraveolens L. var rapaceum (Mill.) DC.) was studied by subjecting plants, after initiation of the primary umbel on the apex, to photoperiods between 8 and 24 h at a temperature of 16 °C.
Apium graveolens is used around the world as a vegetable, either for the crisp petiole (leaf stalk) or the fleshy toproot. The closely related Apium bermejoi from the island of Minorca is one of the rarest plants in Europe, with fewer than 100 individuals left.