BSBI Species Accounts Archive

A rhizomatous perennial of open, sedge-rich areas in calcareous flushes, marshes, fens and damp grassland (sometimes slightly saline as at Marcham in Berkshire) and pond and stream borders subject to flooding. It also occurs in brackish ditches at the head of saltmarshes (Halliday 1997), dune slacks where it appears to share the same niche as Juncus balticus (Smith 1984) and alluvial ‘meadows’ that have developed on stabilized shingle (Graham 1988). On chalk downland it is confined to spring-lines, and coastal populations occur in dune slacks presumably enriched by shell-sand. It appears to favour transitional habitats (Westhoff & van Leeuwan 1962), and almost always occurs where there is some movement of base-rich groundwater even in acid Sphagnum bogs where springs ensure a constant supply of base-richness (e.g. chalybeate springs in the New Forest; Brewis et al. 1996). In v.c. 80 and 81 Blysmus compressus has most of its colonies in a very distinct burnside habitat – a shelf below normal bank level burn occupied by short grass turf. On the North Tyne it also occupies the extreme riverside edge niche in inundated habitats such as rocky spits or islets growing with species such as Trollius europaeus. It is much rarer in the more strongly flushed areas, as the vegetation is much too tall for it. On moorland it can occupy flushes as the associates do not compete so strongly with it. It is not mentioned in the NVC although Graham (1988) records it from Carex dioica-Pinguicula vulgaris mires (M10) in County Durham. This is probably the typical community in Northern England where it grows with rarities such as Bartsia alpina and Juncus alpinoarticulatus. In southern and eastern England it occurs in species-rich fen meadows including MG8 Cynosurus cristatus-Caltha palustris grassland and M23 Juncus effusus/acutiflorus-Galium palustre mire. Grazing is important in keeping these habitats open although both over- and under-grazing are likely to be detrimental in the longer term. The flowers are hermaphrodite and wind-pollinated with fruiting continuing until September. Little is known about its seed or reproductive biology.