Constant species

Lythrum portula, Ranunculus flammula.

Rare species

Alopecurus aequalis, Pilularia globulifera.

Physiognomy

The Lythrum portula-Ranunculus flammula community comprises generally open vegetation in which L. portula and R. flammula are the only constants, the former sometimes occurring with abundance, occasionally in locally monodominant stands. Apart from Eleocharis palustris, other associates are recorded rather sporadically and only rarely with high cover values, but can be quite varied: Agrostis stolonifera, Juncus bufonius, J. effusus, J. articulatus, Galium palustre, Callitriche stagnalis, Littorella uniflora, Mentha aquatica, Alisma plantago-aquatica, Myosotis scorpioides and Apium inundatum have all been found here. The community also provides a locus for the nationally rare Pilularia globulifera, a perennial plant but one quick to colonise the damp open muds characteristic of this vegetation (Jermy in Stewart et al. 1994), Limosella aquatica, an ephemeral herb, and Alopecurus aequalis, an annual grass which invades here as water levels drop (Hubbard 1984, Twist in Stewart et al. 1994).

Habitat

The Lythrum-Ranunculus community is typical of silty or peaty soils, wetted and exposed by fluctuating or temporary waters around pool, lake and reservoir margins and in flooded gravel and brick-earth workings.

Compared with the habitats of Bidention assemblages, the situations colonised by this vegetation are not nutrient-rich and, though the cover of the sward can be extensive, the herbage does not have the lush character of those nitrophilous ephemeral communities.