Synonymy

Grass fen Pallis 1911 p.p.; Late Juncetum Clapham 1940 p.p.; Juncetum subnodulosi Lambert 1946, 1948; Fen meadow Rose 1950, Willis & Jefferies 1959 p.p., Crompton 1972; Rich-fen meadows Wheeler 1980c p.p.

Constant species

Cirsium palustre, Equisetum palustre, Filipendula ulmaria, Holcus lanatus, Juncus subnodulosus, Lotus uliginosus, Mentha aquatica, Calliergon cuspidatum.

Rare species

Peucedanum palustre, Homalothecium nitens.

Physiognomy

The Juncus subnodulosus-Cirsium palustre fen-meadow comprises vegetation which has a readily-recognisable general stamp but which shows considerable variation in its floristic composition. The community has a fairly substantial group of constants and numerous occasional to frequent species can make the vegetation very rich, but this associated flora shows considerable variation from stand to stand, with some plants that are of only low to moderate frequency throughout showing local prominence, and widely-represented species sometimes being locally absent. Often here, such differences reflect unique and complex histories of mowing and grazing, treatments of major importance in maintaining this kind of vegetation.

The most prominent structural element in the community typically comprises rushes and sedges of moderate stature, the abundance of which gives the vegetation the appearance of a rank sward, at least when viewed from a distance. In ungrazed stands, the herbage commonly attains 50-80 cm in height, exceptionally up to 1 m, and it can be dense and rather uniform; where stock have access, the dominants may be sparser or distinctly patchy, clumps of the more resistant plants scattered through the stretches of closer-cropped sward. Prime among the bulkier species is Juncus subnodulosus, a plant of broad occurrence in a wide variety of fen types and some swamps, and sometimes only sparsely-represented here, but able to attain its peak of abundance in this community and the most usual dominant. It is a farcreeping rhizomatous perennial, producing an annual crop of sterile shoots in the autumn, borne singly and bearing but a single leaf, but arising so closely on the rhizomes, at 1-3 cm apart, as to be able to produce a very thick and even cover. These shoots elongate to their full height in the spring, when the fertile shoots are also produced, flowering in July and August (a little later to the north), but then often lodging in autumn winds and rain to form a thick and heavy mattress.