Physiognomy and Structure: No Data Available

Floristics: This association represents vegetation consisting of a dense growth (90% cover) of tall (1-3 m), light-demanding, native perennial herbs. Scattered shrubby or occasionally full-sized trees of flood-tolerant species may occur, with Acer saccharinum, Platanus occidentalis, Betula nigra, Liriodendron tulipifera, Fraxinus pennsylvanica, and Acer negundo the most frequent. Along the Potomac River in the Great Valley of Virginia downstream to the fall line, the most abundant herbs are Verbesina alternifolia, Teucrium canadense, Elymus riparius, Verbena urticifolia, Conoclinium coelestinum (= Eupatorium coelestinum), several species of Eupatorium (Eutrochium fistulosum (= Eupatorium fistulosum), Eupatorium perfoliatum, Eupatorium serotinum), Dichanthelium clandestinum, Scrophularia marilandica, and Chasmanthium latifolium. Less abundant species include Ageratina altissima, Elymus villosus, Elymus virginicus, Helianthus decapetalus, Oenothera biennis, Phytolacca americana, Monarda fistulosa, Rudbeckia laciniata, Calystegia sepium, and Solidago gigantea. Tall annual species characteristically dominant on less stabilized bars may be present but generally do not dominate. Woody vines are often common and include Toxicodendron radicans, and Vitis riparia. Along the New and Bluestone rivers in West Virginia, herbs with high constancy and/or cover include Amphicarpaea bracteata, Apios americana, Boehmeria cylindrica, Chasmanthium latifolium, Conoclinium coelestinum, Dichanthelium clandestinum, Elymus canadensis, Elymus riparius, Elymus virginicus, Eutrochium fistulosum, Eupatorium serotinum, Helenium autumnale, Helianthus strumosus, Heliopsis helianthoides, Leersia virginica, Packera aurea, Phlox paniculata, Polygonum scandens, Polygonum virginianum, Rudbeckia laciniata, Senna hebecarpa, Solanum carolinense, Solidago canadensis, Solidago gigantea, Symphyotrichum lanceolatum, Symphyotrichum lateriflorum, Tradescantia ohiensis, Tripsacum dactyloides, Verbena urticifolia, Verbesina alternifolia, Verbesina occidentalis, and Vernonia noveboracensis. Vascular plant richness is generally high: in West Virginia plots, values range from 41-80 species per 400 m2, averaging 44.6 (Vanderhorst et al. 2008). This type often has a number of invasive exotic weeds, including Fallopia japonica var. japonica, Polygonum perfoliatum, Schedonorus arundinaceus (= Festuca arundinacea), Phalaris arundinacea, Humulus japonicus, Glechoma hederacea, Microstegium vimineum, Urtica dioica, and Stellaria media. In some locations, non-native species may out-compete the native herbs in this association and form large monospecific patches in floodplain openings, especially those affected by reservoir backup. On the Potomac River above the Great Valley, on the Monocacy River, and on smaller streams outside the Great Valley, several of the more characteristic species for the Shenandoah River, Antietam Creek, and the rest of the Potomac are apparently rare or absent, particularly Rudbeckia laciniata and Solidago gigantea. These differences may reflect the influence of more calcareous substrates and/or stream order on the communities. Hasteola suaveolens, Sida hermaphrodita, Iresine rhizomatosa, Rumex altissimus, and Ruellia strepens are Maryland rare species known from this type. Some examples at Mammoth Cave National Park, Kentucky also contain Xanthium strumarium, Vernonia gigantea ssp. gigantea (= Vernonia altissima), Echinochloa muricata, Dipsacus fullonum (= Dipsacus sylvestris), and Setaria parviflora, in addition to many of the species recorded at other sites.

Dynamics:  During years of more continuous high water during the growing season, vegetation may be sparse. Comparison of the frequency of this type at New River Gorge and nearby Bluestone National Scenic River noted that "the rate and extent of sedimentation has been greatly increased by flooding of Bluestone Lake, probably increasing the extent of this association. It can also occur as successional vegetation on floodplains previously cleared for agriculture" (Vanderhorst et al. 2008).