Synonymy

Valley moor plashes Rankin 1911 b p.p.; Hyperico-Potamogetonetum sensu Birse 1980, Ratcliffe & Hattey 1982, Dierssen 1982; Flushing Water Community NCC New Forest Bogs Report 1984 p.p.

Constant species

Hypericum elodes, Juncus bulbosuslkochii, Potamogeton polygonifolius, Ranunculus flammula, Sphagnum auriculatum.

Rare species

Galium debile, Pilularia globulifera.

Physiognomy

The Hyperico-Potametum polygonifolii has a very distinctive appearance, typically consisting of low creeping or floating mats of Hypericum elodes and Potamogeton polygonifolius, the former prominent with its soft tomentose shoots, the flowering ones shortly erect, against the olive-green foliage of the latter, lying flat on the surface of the water or the wet soil of the small runnels and pools in which this vegetation characteristically grows. Very often, except where the ground has been badly trampled by grazing animals, a feature of some of the stands included in Ratcliffe & Hattey (1982) and the NCC New Forest Bogs Report (1984), these two constants are set in a carpet of more or less submerged Sphagnum auriculatum, sometimes accompanied by S. cuspidatum, S. palustre or S. recurvum, and very occasionally with small patches of S. papillosum growing on the slightly raised areas. But other bryophytes are typically sparse: some stands show a modest local abundance of Polytrichum commune or Aulacomnium palustre, and Drepanocladus exannulatus, D. revolvens and Calliergon cuspidatum can also be found, but enrichment of this element of the vegetation is rare.

Neither is the associated vascular flora very extensive or consistent, being frequently confined to scattered plants of a variety of bog and poor-fen herbs, growing among the dominants or projecting above them as a very open canopy. Only Juncus bulbosus (very occasionally recorded as J. kochii) and Ranunculus flammula attain constancy among the companions but, of smaller species, Hydrocotyle vulgaris, Anagallis tenella, Drosera rotundifolia, Narthecium ossifragum and Galium palustre, all occur with moderate frequency, together with such sedges as Carex demissa, C. echinata, C. panicea and C. nigra. Then, there can be sparse shoots or small patches of Molinia caerulea, Agrostis canina ssp. canina, Juncus articulatus, J. effusus, J. acutiflorus, Eleocharis multicaulis, Eriophorum angustifolium and Rhynchospora alba.