Physiognomy and Structure: Grasses and forbs dominate this group with shrubs and trees sometimes present but with less than 25% cover. The herbaceous stratum is generally 0.5-1 m tall with some stands dominated by species approximately 2 m tall. Perennial species are typically most abundant but sites in the western part of the group''s range or those that were recently disturbed may have significant amounts of annuals.

Floristics: Examples range from having a mix of species to sites strongly dominated by one or two species. Abundant species vary across the group, depending on land-use history, including what may have been planted on the site, nearby seed sources, whether a site is mesic or dry, and other factors. Common abundant or dominant species include the grasses Agropyron cristatum, Agrostis gigantea, Agrostis stolonifera, Bromus inermis, Lolium perenne, Phleum pratense, Poa annua, Poa pratensis, and Thinopyrum intermedium and the forbs Ambrosia spp., Cirsium arvense, Cirsium vulgare, Euphorbia esula, and Melilotus officinalis. Other common species include the annual grasses Bromus arvensis, Bromus catharticus, Bromus hordeaceus, Bromus racemosus, Bromus secalinus, Bromus tectorum, Digitaria spp., Setaria faberi, Setaria italica, Setaria pumila, Setaria verticillata, and Setaria viridis and the forbs Bassia scoparia, Carduus spp., Centaurea spp., Chenopodium album, Datura stramonium, Lotus corniculatus, Rumex acetosella, Rumex crispus, Salsola spp., Sonchus spp., Trifolium arvense, Trifolium aureum, Trifolium campestre, Trifolium dubium, Trifolium hybridum, Trifolium repens, and Trifolium pratense.

Dynamics:  Examples of this group are, by definition, a result of a change in ecological processes or a direct introduction of exotic species. This is usually the result of some combination of a reduction in fire frequency, increased grazing pressure, intentional planting of exotic species or the unintentional spread of exotic species from nearby sources. Many of the exotic species are persistent once they are established on a site so reversion to a native vegetation type is not certain even if the disturbance that allowed the formation of this group is removed.