A perennial herb of base-rich fens, reed-beds and fen-meadows; also, rarely, on marshy ground by rivers. Lowland.
L. palustris was lost from many sites in E. England before the end of the 19th century, and is still declining there due to drainage and lack of management. New populations have been discovered in Wales and Kintyre since 1970. One of these, which grew at Tywyn Burrows (Carms.) but has since disappeared, was the American var. pilosus, which probably originated as a drift seed. L. palustris is thought to be increasing in Ireland and is certainly better recorded there than in the 1962 Atlas.
Circumpolar Boreo-temperate element.
Light (Ellenberg): 7
Moisture (Ellenberg): 9
Reaction (Ellenberg): 7
Nitrogen (Ellenberg): 4
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.9
July Mean Temperature (Celsius): 15.4
Annual Precipitation (mm): 823
Height (cm): 120
Perennation - primary
Life Form - primary
Comment on Life Form
Clonality - primary
Comment on Clonality
Count of 10km squares in Great Britain: 57
Count of 10km squares in Ireland: 36
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.23
Scarce Atlas Account
Lathyrus palustris L.
L. palustris is a perennial that climbs and scrambles over coarse vegetation. Its preferred habitats are base-rich and wet with tall grass, reed or scrub cover. In particular it is characteristic of rich fens in Britain, although on the continent of Europe it is more typical of habitats such as wet coarse grasslands and hay meadows on peat. It prefers well-lit sites on base-rich soils which are deficient in nitrogen. Characteristic associates include Calamagrostis canescens, Cladium mariscus, Eupatorium cannabinum, Juncus subnodulosus, Lysimachia vulgaris, Lythrum salicaria, Mentha aquatica and Phragmites australis. Peucedanum palustre and Thelypteris palustris grow with L. palustris at several of its eastern localities. This species is confined to the lowlands of Britain.
L. palustris spreads by seeds, but is a long-lived perennial.
L. palustris is declining in the eastern half of its British range, even within its strongholds in Broadland. It has declined in Fenland due to drainage and site destruction, whilst in wet hay-meadows, grassland improvement and reseeding have eliminated or modified the habitat. In Wales, however, several sites have been discovered since 1970, and the species was also discovered in Kintyre in 1976.
L. palustris has a very wide world distribution, being found throughout Europe, temperate and arctic Russia east to the Pacific, and temperate North America. It is rare in the Mediterranean region.
The American var. pilosus (Cham.) Ledeb. persists at one site in a seasonally flooded dune slack at Tywyn Burrows (Vaughan 1978). It has been suggested that this population has its origins as a drift seed, having floated across from America on the North Atlantic Drift.
J. O. Mountford