Physiognomy and Structure: This aquatic alliance is characterized by >25% cover by floating, unrooted herbaceous species and <25% cover by emergent species.

Floristics: Lemna spp. Spirodela polyrrhiza, and Wolffia spp. typically dominate but may be mixed with other plant taxa. These small plants may float on the water''s surface or become stranded and possibly rooted during drawdown periods. The composition of examples varies across this wide distributional range. Lemna taxa that may be present in eastern North America include Lemna aequinoctialis (southwest U.S. as well as southeast U.S.), Lemna minor (widespread across temperate North America), Lemna minuta (widespread across southern U.S.), Lemna obscura (eastern-southeastern U.S.), Lemna perpusilla (eastern U.S.), Lemna trisulca (widespread temperate and boreal, but not southeast U.S.), Lemna turionifera (widespread temperate and boreal, but not southeast U.S.), and Lemna valdiviana (southeast U.S., and spotty in the southwest U.S.). Other species present may include Spirodela polyrrhiza (widespread temperate U.S.), Landoltia punctata (= Spirodela punctata) (southeastern U.S.), Azolla microphylla (= Azolla mexicana), Azolla filiculoides, Wolffiella lingulata (rare), Wolffiella oblonga (extreme southwest and southeast U.S.), Wolffiella gladiata (southeast coastal plain), Wolffia brasiliensis (eastern temperate U.S.), Wolffia borealis (west coast temperate and eastern temperate U.S., but not coastal plain), Wolffia globosa (eastern temperate U.S.), and Wolffia columbiana (eastern temperate U.S.), as well as Riccia spp. (aquatic liverworts). Associated rooted floating aquatics include Potamogeton spp., Sagittaria spp., or Polygonum spp. may also be present. While these latter species are rooted submerged species, and technically not part of the strictly floating community, they do intermingle. Biomass can be abundant under eutrophic conditions.

Dynamics:  This alliance can move easily as wind blows the unrooted dominant species around lakes and ponds.