Fifteen of the sixteen extant populations in Massachusetts and Rhode Island occur on the upper margins of sandy to peaty shores of coastal plain ponds (MANHESP 1986, Elliman 2001). The plants typically grow in full sun or partial shade. One population in Rhode Island grows in a boggy meadow along the margin of a shrub thicket (Elliman 2001.). Coastal plain ponds in southern New England are relatively nutrient-poor habitats formed by glacial action on the coastal plain. Water levels in the ponds fluctuates markedly seasonally and from year to year, tied to groundwater level and rainfall. Few plant species can withstand this challenging cycle of inundation and drought. Eupatorium leucolepis var. novae-angliae can go dormant during years when water levels are high, relying on reserved from its starchy rhizomes. When water levels drop, the plant reappears, along with other rare coastal plain plant species. If the magnitude of these water fluctuations diminishes due to diversion or pumping of groundwater, or if nutrients are loaded into the pond from septic leaching and surface run-off, other plant species can gain a foothold in these ponds and readily outcompete these rare specialists.Plants associated with the taxon at various sites include an array typical of coastal plain ponds: Acer rubrum, Agalinis paupercula, Agrostis sp., Alnus serrulata, Aster lateriflorus, Betula populifolia, Bidens sp., Calamagrostis canadensis, Cladium mariscoides, Coreopsis rosea, Cyperus dentatus, Drosera filiformis, Eriocaulon aquaticum, Euthamia tenuifolia, Fuirena pumila, Gratiola aurea, Hypericum sp., Iris versicolor, Juncus canadensis, Juncus greenei, Juncus pelocarpus, Lycopus sp., Lyonia ligustrina, Lysimachia terrestris, Myrica pensylvanica, Pinus rigida, Rhexia virginica, Rhyncospora capitellata, Rumex sp., Sabatia kennedyana, Sagittaria teres, Salix sp., Scirpus americanus, Spiraea latifolia, Spiraea tomentosa, Stachys hyssopifolia, Vaccinium corymbosum, Viola lanceolata, and Xyris sp. (Elliman 2001).