Physiognomy and Structure: This alliance is characterized by a rhizomatous perennial that dominates the graminoid stratum (up to 70% cover). The forb layer is sparse (0-20%) and contains both aquatic and terrestrial species.

Floristics: Associations within this alliance are dominated by Eleocharis palustris and/or Eleocharis macrostachya. Cover ranges from sparse to quite dense (10-80%). Distichlis spicata and Muhlenbergia asperifolia codominate the graminoid layer in cienegas (Arizona and New Mexico). Forb cover is composed of Berula erecta and Nasturtium officinale (= Rorippa nasturtium-aquaticum), especially in stands with deep water (Cross 1991). At higher montane elevations, other graminoids present include Carex aquatilis, Carex buxbaumii, Carex utriculata, Deschampsia cespitosa, Juncus arcticus ssp. littoralis (= Juncus balticus), and Eleocharis rostellata. Forb cover is typically low, but can be up to 25% in some stands. Common forb species include Caltha leptosepala, Pedicularis groenlandica, and Rhodiola integrifolia (Hansen et al. 1995, Kittel et al. 1999a). Crowe and Clausnitzer (1997) state that Eleocharis palustris is an aggressive species, typically excluding other species from establishing. In Oregon stands, associated forbs include Iris missouriensis, Mentha arvensis, Ranunculus cymbalaria, and Rumex crispus.

In California, forb cover can be quite high, and a mixture of forbs will infrequently dominate the community. However, it is the cover of Eleocharis, which typically exceeds 50%, that distinguishes this community from others with high forb cover. Forbs present include Berula erecta, Centaurea solstitialis, Euthamia occidentalis, Hydrocotyle umbellata, Melilotus indicus, Mentha arvensis, Mimulus guttatus, Perideridia parishii, Polygonum bistortoides, Pseudognaphalium canescens ssp. beneolens (= Gnaphalium canescens ssp. beneolens), Ranunculus californicus, Nasturtium officinale, Sonchus asper (= ssp. asper), Stachys pycnantha, Symphyotrichum spathulatum (= Aster occidentalis), Trifolium wormskioldii, and Urtica dioica ssp. holosericea. In vernal pools and other seasonally flooded wetlands, other forbs include Eryngium castrense and/or Eryngium vaseyi, Juncus sp., Plagiobothrys stipitatus var. micranthus, and Psilocarphus brevissimus var. brevissimus. Graminoids present include the characteristic Eleocharis macrostachya, with Aira caryophyllea, Bromus arenarius, Bromus hordeaceus, Carex barbarae, Carex nebrascensis, Carex spp., Eleocharis acicularis, Eleocharis rostellata, Juncus bufonius, Juncus effusus var. pacificus, Juncus nevadensis, Lemna minor, Lolium perenne ssp. multiflorum (= Lolium multiflorum), Polypogon monspeliensis, Schoenoplectus americanus (= Scirpus americanus), and Vulpia myuros.

Dynamics:  At lower elevation, Eleocharis palustris plant associations occur well within the active channel and are inundated annually. These early-seral communities colonize backwater eddies and shallow edges of slow-moving reaches of small and larger rivers. The stands are probably ephemeral, as the eddies and river edges are scoured out each year during high spring flows (Kittel et al. 1999a). These communities have also been described as early-seral stages by Padgett et al. (1989), who describe light-colored soils for the sites, indicating an early phase of soil development. Kovalchik (1987) reports that the lower elevation plant associations within this alliance frequently form seral communities in ponded sites between stream rehabilitation structures such as loose rock check dams. In the montane zone, associations within this alliance occur in ponded sites on faster moving streams. If siltation occurs, sites may become dominated by Carex utriculata. At higher elevations, the associations appear to be stable. Stands occur near seeps on soils with deep organic layers, often sapric, and are saturated throughout the growing season.

Crowe and Clausnitzer (1997) state that Eleocharis palustris is of little to no forage value to livestock and wild ungulates. On seasonally drier sites, ungulate trampling may cause this species to increase (Snyder 1992 as cited in Crowe and Clausnitzer 1997). However, this species does provide seed forage and cover to ducks and geese (Kovalchik 1987).