Eupatorium cannabinum (Asteraceae), a New Species for New England

We report the presence of Eupatorium cannabinum L. (hemp agrimony) growing spontaneously in Dukes County, Massachusetts, in Edgartown on Martha’s Vineyard. This species has not been documented previously in New England (Angelo and Boufford 2020). The native range of E. cannabinum is Europe to central Asia and northwestern Africa (Plants of the World Online 2019). Considered a garden escapee in the United States, it has been documented in New York, Pennsylvania, Maryland, and Virginia in the United States, and is possibly naturalized in British Columbia in Canada (National Resources Conservation Service 2021). In New Zealand, E. cannabinum has been reported to be invasive (Global Invasive Species Database 2021). Eupatorium cannabinum is a perennial herb that grows to 1.5 m tall (Siripun and Schilling 2006). It is typically found in disturbed (Siripun and Schilling 2006) and wet sites (Global Invasive Species Database 2021). We found the plants on conservation land within 60 m of a freshwater pond. Hundreds of flowering stems were present in a lightly shaded thicket at the base of a slope and extending a short distance upslope. They occupied an area measuring approximately 16 × 13 m. A single plant in occasionally mowed trailside brush in light shade was located 40 m distant. Accompanying plants included Acer rubrum L., Ampelopsis glandulosa (Wall.) Momiy. var. brevipedunculata (Maxim.) Momiy., Artemisia vulgaris L., Calystegia sepium (L.) R. Br. subsp. americana (Sims) Brummitt, Clethra alnifolia L., Eupatorium perfoliatum L., Euthamia graminifolia (L.) Nutt., Hedera helix L., Holcus lanatus L., Juncus pylaei Laharpe, Lonicera japonica Thunb., Prunus serotina Ehrh., Quercus velutina Lam., Solidago rugosa Mill., Symphyotrichum novi-belgii (L.) G.L. Nesom, Toxicodendron radicans (L.) Kuntze, and Viburnum dentatum L. We identified our plants as Eupatorium cannabinum using the key of Siripun and Schilling (2006): leaves (at least larger proximal) palmately 3(–5)-lobed; the lobes relatively broad (20–40 mm); margins serrate; corollas usually pinkish. Other notable features