Sium is a genus of roughly 12 species of perennial flowering herbs in the carrot family, Apiaceae (order Apiales). Members of the genus are commonly known as water parsnips, a name that reflects both their affinity for wet habitats and their superficial resemblance to the cultivated parsnip.
Plants are typically found growing in or alongside standing and slow-moving water — marshes, stream banks, pond margins, and wet meadows. Stems are branching and often root at the nodes when in contact with moist soil or water. The lower leaves are pinnate, divided into toothed leaflets that arise on petioles whose bases sheath the stem. Flowers are small and white, arranged in characteristic compound umbels typical of the Apiaceae.
The genus has a broad distribution across temperate regions of Europe, Asia, Africa, and North America. Notable species include Sium latifolium (great water parsnip), widespread across Eurasia; Sium suave (common water parsnip), found in North America; and Sium sisarum (skirret), a species with a long history of cultivation in Europe and Asia as a root vegetable.
Distribution
Sium is widely distributed across temperate and subtropical regions of Europe, Asia, Africa, and North America. Species typically occupy wetland habitats — including marshes, pond margins, stream banks, and wet meadows — across this broad range.
Ecology
Water parsnips are characteristic wetland plants, growing in marshes, along stream banks, and at the margins of ponds and slow-moving water. Some species are partially to fully aquatic, with stems that root at nodes when submerged or in contact with waterlogged soil. The compound umbel flowers are visited by a range of small insects.
Cultural Uses
Sium sisarum (skirret) is the best-known economically important member of the genus, cultivated since antiquity in Europe and Asia for its cluster of sweet, edible roots. It was a staple root vegetable in medieval European kitchens before the wider adoption of the potato. The remaining species are not generally used as food plants, and several superficially resemble toxic umbellifers, warranting caution in identification.
