Greater Water-parsnip

Sium latifolium

Greater Water-parsnip is an impressive, tall plant that is declining fast


Greater Water-parsnip is a large, robust plant, up to 200cm tall. White umbellifers can look very similar, but Greater Water-parsnip has some distinctive distinguishing features. It has hairless, hollow and ridged, green stems which strongly smell of paraffin or petrol. Stem leaves are 1-pinnate (which means that each leaf is divided once, rather than multiple times), and each of these divided leaves is comprised of 3-7 pairs of leaflets. The leaflets are lanceolate in shape and the edges are finely toothed; they attach directly to the leaf stem (no leaf stalk) and can be up to 12cm long and 4cm wide. Greater Water-parsnip has white flowers held in umbels at the end of the plant stem. Flowers can be seen in July and August, and the plants die back soon after flowering.


Greater Water-parsnip likes damp or wet calcareous habitats, usually in areas of winter flooding. It occurs in meadows and pastures in the flood plains of rivers, in marshes and fens, and in emergent and fringing vegetation by rivers, streams, canals, ditches, lakes and ponds.

Distribution and threats

Greater Water-parsnip has declined rapidly over the last 200 years, mostly due to the drainage of wetlands and loss of suitably managed habitats. Greater Water-parsnip is particularly sensitive to the right amount of disturbance. Not enough disturbance and the habitat become scrubbed over, too much grazing and the plants are eaten and the habitat trampled. With intensification and increased numbers of stock on smaller fields and fencing of pond and river margins, the conditions at many historic sites are now unsuitable. It is classified as Scarce in the UK, due to its still widespread but declining range. It is a Priority Species for conservation in both England and Wales.