This perennial herb was once typical of very wet, species-rich, tall-herb fen, which often developed as floating mats at the margins of lakes and large rivers; now it is generally found in ditches, growing amongst other emergent species or in reedswamp. It prefers alkaline conditions. It is readily grazed by stock, and often restricted to inaccessible ditch-banks. Lowland.
The substantial decline of this species was already apparent in the 1962 Atlas and has continued since then, largely due to the effects of habitat destruction, drainage, reclamation and changes in the management of water levels.
Eurosiberian Temperate element.
Count of 10km squares in Great Britain: 259
Count of 10km squares in Ireland: 34
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -1.83
Scarce Atlas Account
Sium latifolium L.
The natural habitat of S. latifolium is the very wet, species-rich, tall-herb fen that develops as a semi-floating raft at the margins of lakes and large rivers. This vegetation is often dominated by Phragmites australis or Typha angustifolia, and S. latifolium is sometimes accompanied by the other scarce umbellifers Cicuta virosa and Peucedanum palustre. However, following the drainage and reclamation of most fens in Britain, S. latifolium is now most often met in drainage ditches, growing in a more species-poor reed-swamp or, more rarely, with a floating mat of Hydrocharis morsus-ranae, Lemnaceae and, in Broadland, Stratiotes aloides. It is frequent in old cuttings in fen peat.
S. latifolium prefers shallow, still or slow-moving water that is alkaline, rich in nitrogen and on a peat or alluvial soil. It is able to tolerate the light shade produced by reeds, but is excluded from can. Although often growing in stands of Bolboschoenus maritimus, S. latifolium is rarely, if ever, found in brackish water. It is confined to the lowlands of Britain, being most common in the coastal levels and flood plains of major rivers.
S. latifolium can live submerged for some years without flowering. It is a perennial which produces abundant seed, but opportunities for seedling establishment are few in tall fen. In ditches, particular individuals survive in tall reed for over 10 years, but recruits are usually only seen following the cutting of the vegetation or the use of a weed bucket.
S. latifolium has undergone a catastrophic decline in Britain in the last 200 years, probably as a result of fen drainage and the elimination or over-engineering of watercourses. Even in many protected sites, decline has been observed and new individuals are rare. Since it is intolerant of grazing and frequent cutting, S. latifolium is often most common in ditches adjacent to unreclaimed fen or arable land, provided the water is kept open by occasional use of a weed bucket or scythe.
S. latifolium is widespread in Europe, but is very rare near the Mediterranean and absent from Portugal. It is rare and mainly southern in Fennoscandia, having also markedly declined in Finland. S. latifolium extends into temperate Siberia, and is recorded in south-eastern Australia, but is unknown in Japan and the Americas.
J. O. Mountford
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
1978. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 2. 2 vols.
1994. Scarce plants in Britain.
1980. Umbellifers of the British Isles. Botanical Society of the British Isles Handbook no. 2.