Synonymy

Fen Association Pallis 1911; Junco subnodulosi-Calamagrostietum canescentis Korneck 1963 p.p.; Cladietum marisci sensu Krausch 1964 p.p. and sensu Westhoff & den Held 1969 p.p.; Scirpo-Phragmitetum sensu Krausch 1964 p.p. and sensu Westhoff & den Held 1969 p.p; Thelypterido-Phragmitetum

Westhoff & den Held 1969 p.p.; Thelypterido-Phragmitetum Kuiper 1957 emend. Segal & Westhoff 1969 p.p.; Peucedano-Phragmitetum australis Wheeler 1978 p.p. and Caricetum paniculatae peucedanetosum Wheeler 1978.

Constant species

Calamagrostis canescens, Cladium mariscus, Eupatorium cannabinum, Filipendula ulmaria, Galium palustre, Juncus subnodulosus, Lysimachia vulgaris, Lythrum salicaria, Mentha aquatica, Peucedanum palustre, Phragmites australis, Calliergon cuspidatum.

Rare species

Carex diandra, C. appropinquata, Cicut a virosa, Lathyrus palustris, Peucedanum palustre, Sium latifolium, Thelypteris palustris.

Physiognomy

The Peucedano-Phragmitetum is a community of herbaceous fen vegetation, somewhat varied in composition but often species-rich and of complex physiognomy (Wheeler 1975, 1978, 198(kz). Tall monocotyledons generally make up the major structural component and, of these, Phragmites australis, Cladium mariscus and Calamagrostis canescens are constant and the most usual dominants. Much less frequent throughout but occasionally dominant are Carex paniculata, Glyceria maxima, Typha angustifolia, Phalaris arundinacea and Calamagrostis epigejos. The gross appearance of the vegetation at any particular time of year depends very much on the phenology of these species and on the fen treatment, if any, but in summer, unmown stands have a characteristically tall canopy, 1-2 m high, of varying density but often sufficiently thick to give stands a superficially uniform appearance.

Intermixed with these helophytes is a variety of tall herbaceous dicotyledons which, though rarely individually abundant, together give the vegetation a typically colourful appearance in the flowering season. Lysimachia vulgaris, Lythrum salicaria, Eupatorium cannabinum, Filipendula ulmaria and Peucedanum palustre are constant, the rare milk parsley having its major locus in this community. Also frequent are Valeriana officinalis, Iris pseudacorus and Lycopus europaeus and, rather more unevenly between the various sub-communities, Angelica sylvestris, Cirsium palustre, Rumex hydrolapathum, Epilobium hirsutum and Symphytum officinale.

Beneath these components, there is a rather variable layer, some 60-80 cm tall, generally dominated by sedges or rushes. Juncus subnodulosus and Carex elata are the most frequent and abundant species here but C. riparia, C. acutiformis, C. appropinquata, C. lasiocarpa or C. diandra can all attain local prominence. In other cases, Molinia caerulea, Schoenus nigricans or Thelypteris palustris are abundant in this layer.