Greater water parsnip (Sium latifolium) - Species Action Plan

A tall hairless perennial with ridged stems. This plant has white flowers arranged in a large globe or umbel. It thrives in ditches and wet fens where water is kept open by occasional clearance with a bucket excavator or mower.
Ref 2/S8 Species Action Plan 8
Plan Author: H Mahon / J Halls
Plan Co-ordinator: Jeremy Halls
April 2004 Draft under Review
Final Draft July 2005

Greater water parsnip
(Photo credit: Jeremy Halls)

Action Plan Summary

Current Status

National Status

  • In the past, greater water parsnip was most commonly found on rafts of semi-floating vegetation at the margins of lakes and large rivers. However, following the drainage and reclamation of fens in the UK, it is now most often found in drainage ditches and wet fens in the east of England. It is widespread in Europe, but very rare near the Mediterranean.

  • In Great Britain, greater water parsnip is classified as Nationally Scarce (ie occurs in 16-100 10km squares), being recorded from 62 10km squares during the latest Atlas recording period (1987-1999). However, its distribution has contracted significantly over the past 100 years with most extant populations being found in major wetland areas such as the Somerset Levels and The Broads. It receives general protection under the Wildlife and Countryside Act 1981.

Norfolk Status

  • Norfolk remains one of the plant's strongholds, although there is evidence of a long-standing decline here too - Ted Ellis in his New Naturalists' book on The Broads (1965) referred to it as 'a rare and disappearing species'. In Broadland, the main populations are found in fen habitat in the Ant valley, although the plant also occurs along some grazing marsh dykes, notably in the Halvergate - Wickhampton area. In the west of the county, there are few recent records, although the plant still occurs in good numbers on the Ouse Washes. On the north Norfolk coast, there are post-1988 records for Holme and Burnham Overy.

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Current factors causing loss or decline in Norfolk

The threats to this species include intensive dyke maintenance, lack of channel maintenance, drainage of sites (including low winter dyke water levels) and exposure to prolonged heavy grazing. It is intolerant of heavy shade and has therefore suffered as a consequence of the progressive invasion of 'open' fen communities by trees and scrub. Eutrophication and other water quality factors may also be a problem.

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Current Action in Norfolk

  • Most of the Norfolk populations of greater water parsnip fall within designated sites, many of which are managed by conservation organisations. 

  • Fen restoration work and scrub clearance currently taking place should benefit this species, while in the grazing marshes agri-environment schemes can provide suitable prescriptions to maintain and enhance populations.

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Action Plan Objectives and Targets


  • Maintain the range of greater water parsnip in the UK.

  • Ensure that viable populations are maintained at all extant sites.

  • Regenerate plants from the seed-bank on five suitable historical sites in England by 2003.

  • Provide opportunities for the spread of greater water parsnip from extant sites.


  • Maintain at least 20 sites for greater water parsnip across its known range (Broadland fens, Broadland grazing marsh, Ouse Washes and north Norfolk coast).

  • Ensure that the population remains viable at all these sites.

  • Provide opportunities for the spread of greater water parsnip from extant sites.

  • Ensure colonisation of two new sites by 2006.

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Management Guidance

(This guidance is a general summary; for detailed information or advice, consult the references or contacts below.)

Management guidance for greater water parsnip tends to be the same as good fen management practice. The plant is intolerant of heavy shade, and is likely to disappear from neglected fen that has been invaded by scrub. Conversely, it is sensitive to heavy grazing pressure and probably suffered a decline during the periods of high coypu populations. Grazing should therefore be sufficient to reduce scrub encroachment but light enough to maintain tall vegetation on dyke edges. Fencing could be considered if grazing pressure is thought to be the only adverse factor in an otherwise suitable site.

The plant thrives where the water table is between 10cm below the surface and 10cm above the surface, but it has a tolerance of 30cm below to 40cm above. Provision of sufficient water is also an important management consideration. It is considered to prefer good quality water, but may be able to tolerate some salinity. Seasonal factors, including extreme winter drawdown of dyke levels are likely to adversely affect survival.

Shallow turf ponding will benefit greater water parsnip as it is really a swampy, rather than a fen species.

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  • Jeremy Halls (Plan Co-ordinator)
    Broadland Environmental Services Limited
    Third Floor, Grosvenor House
    112-114 Prince of Wales Road
    NR1 1NS
    Tel: 01603 226161

  • Martin George 
    Marsh House
    NR13 4HT
    Tel: 01603 712082

  • Gillian Beckett
    Bramley Cottage
    Docking Road
    King’s Lynn
    PE31 8QF
    Tel: 01485 518225 

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Key References and Bibliography

  • Beckett, G, Bull, A & Stevenson, R. 1999. A Flora of Norfolk. Privately published.

  • Halls, J.M. 2005. Sium latifolium species records for Norfolk. Unpublished.

  • Preston, C D, Pearman, D A & Dines, T D (eds). 2002. New Atlas of the British and Irish Flora. Oxford: Oxford University Press

  • Rodwell, J S (ed). 1995. British Plant Communities 4. Aquatic communities, swamps and tall-herb fens. Cambridge: Cambridge University Press.

  • Stewart, A, Pearman, D A, and Preston, C D (eds). 1994. Scarce Plants in Britain. Peterborough: JNCC

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