Physiognomy and Structure: No Data Available

Floristics: Vegetation may be sparse during years of more continuous high water during the growing season. In normal growing seasons, the type is a dense growth of tall (1-2 m) predominantly annual herbs. Some weedy, fast-growing perennials are also characteristic. These include Amaranthus spinosus, Artemisia annua, Datura stramonium, Eupatorium serotinum, Polygonum lapathifolium, Polygonum pensylvanicum, Polygonum punctatum, Teucrium canadense, Verbesina alternifolia, and Verbena urticifolia, which are relatively constant and generally contribute most of the cover. Additional, less constant or abundant species include Dysphania ambrosioides (= Chenopodium ambrosioides), Conoclinium coelestinum (= Eupatorium coelestinum), Hibiscus laevis, Mollugo verticillata, Perilla frutescens, Polygonum cespitosum var. longisetum, Solanum carolinense, Solanum ptycanthum, Teucrium canadense, Urtica dioica ssp. dioica, Verbena hastata, and Verbesina alternifolia. Herbaceous vines may also be numerous, with Calystegia sepium, Cynanchum laeve, and Cuscuta gronovii most frequent. Scattered individuals of shrubby to full-sized flood-tolerant trees (e.g., Platanus occidentalis, Acer saccharinum) may be present.

Dynamics:  In habitats occupied by this community, sediment deposition is apparently frequent enough and sediment turnover extensive enough during even relatively small floods that most established perennial species are quickly buried or scoured away. These conditions favor the prevalence of annual herbs and rapidly growing perennials, both of which probably produce extensive seedbanks. It is uncertain whether this association is fully natural, as approximately 30% of its characteristic species are not indigenous to the region. While it is likely that this vegetation has been altered in both composition and distribution by anthropogenic watershed changes increasing the frequency and level of floods on the Potomac (favoring annual species and exotics), it also seems reasonable to presume that some similar form of low, frequently flooded depositional bar originally occurred along higher gradient stretches of the very powerful Potomac River. For now, the type is classified as a natural type that, like most floodplain communities, has been altered to a considerable degree by post-settlement disturbances. Multi-year research would be needed to elucidate competitive dynamics of this community type and to fully evaluate its conservation value.