Greater Water Parsnip Replanted

The greater water parsnip, Sium latifolium, is a plant of fens and wet ditches which grows in still or slow-moving water, sometimes emerging from rafts of floating vegetation. It grows to 2m in height, producing large umbels of white flowers in mid to late summer. Despite being related to the culinary parsnip, it is, like many other umbellifers, poisonous. Restricted to floodplains and fens to the east and south of England, the population of this plant has suffered a sharp decline in the last 40 years, mainly due to the destruction of its habitat through drainage, land reclamation and changes in the way water levels are managed. It may also be affected by high levels of nutrients in water caused by fertiliser run-off. Now categorised by the IUCN as Endangered, Sium latifolium is also a priority species for the UK Biodiversity Action Plan. In Oxfordshire, the Oxford Flora Group are actively involved in the conservation of this species (among many others). Last year, the Botanic Garden raised plants from seed collected in an SSSI near Wytham, to provide the Oxford Flora Group with plants to reintroduce at the same site, helping to boost the population.

Collecting seed from Sium latifolium

On a sunny day at the end of september, staff from the Botanic Garden joined Dr. Judy Webb, who is flora guardian for Sium latifolium to collect more seed from the Wytham site and to plant out eleven young plants raised at the garden. We were careful to choose stretches of ditch where competition would be minimal.

Given the chance to grow in its preferred habitat, we hope that this beautiful and striking plant will begin to recover from its decline. We were delighted to be able to reintroduce plants of local provenance to this site and we are sowing many more seeds in order to have more plants to return to the site next year.

Three Sium latifolium plants, newly installed

All photographs Dr. Judy Webb