Physiognomy and Structure: Perennial herbaceous graminoids and forbs typically <1 m tall dominate the group, though annuals or a mix of annuals and perennials can dominate some areas. Composition varies depending on the depth and duration of flooding and on substrate, with stands occurring over limestone bedrock in the Edwards Plateau often having some differences from those on deep soils in the Great Plains.

Floristics: Species richness varies considerably among individual examples of this group. Common perennials are Pascopyrum smithii, Panicum obtusum, Panicum virgatum, and Bouteloua dactyloides (= Buchloe dactyloides); the first two in particular may form lush stands in some cases. Sites that are dry most of the growing season but where flooding duration is too long for the upland perennials to thrive typically have more annuals. These include Cyperus spp., Echinochloa spp., Mollugo verticillata, and Polygonum spp. Those examples in the Edwards Plateau typically are dominated by Bouteloua dactyloides, Chaetopappa bellidifolia, Paronychia spp., Pleuraphis mutica, Sedum nuttallianum, Sedum pulchellum, Sporobolus vaginiflorus, and the alga Nostoc commune.

Dynamics:  Playas have a large change in hydrologic status over much of their areas. That is, most of the area of an individual playa is wet or flooded at one point in the growing season but dries out for much of the growing season. Some do have deeper areas that are wet or flooded for nearly the entire growing season but those do not fit within this group (they likely fall within ~Great Plains Freshwater Marsh Group (G325)$$ or ~Arid West Interior Freshwater Marsh Group (G531)$$). Multiple wet-dry cycles during one growing season in response to rain and dry periods is more common. This rapid change in available moisture and in exposed soil limits the species that can grow. This often results in strong dominance by a few perennial species able to tolerate these conditions or by annuals that can go through their life cycle before conditions change (Haukos and Smith 1993). However, the unconnected nature of playas combined with the variable environmental conditions throughout the year favors the formation of differing assemblages of vegetation at any one time on playas across the landscape. This contributes to regional diversity of plant and animal habitats throughout the year (Haukos and Smith 1994). Fire can spread into this system from surrounding grasslands but it is uncommon. The surrounding grasslands are typically short to mid grasses and do not have sufficient fuel to carry fire well and, while playas usually have more dense vegetation cover than the adjacent uplands, they may be wet.