OCCURRENCE OF THYMELEAF SANDMAT EUPHORBIA SERPILLIFOLIA IN VERMONT

We report that a small, naturalized population of Euphorbia serpillifolia Pers. was discovered in Grand Isle County, Vermont, in 2015, a new state record. It has persisted and was vouchered by JGM in 2018. The population is growing on disturbed limestone boulders and gravel of a boat launch along the shoreline of Lake Champlain below West Shore Road just north of Eagle Camp Road in South Hero, Vermont. The range of Euphorbia serpillifolia is mostly west of the Mississippi River (Berry et al. 2016), though Gleason and Cronquist (1991) note that it is occasionally introduced eastward. While occasionally present in New York and Eastern Canada (Berry et. al. 2016; USDA 2019), in New England the species has only been reported naturalized in Gorham, Coos County, New Hampshire (Haines 2011; Pease 1964). The only known voucher records of E. serpillifolia in New England are one collected from a garden (not naturalized) in 1911 in Middlebury, Vermont, (The Pringle Herbarium [VT], UVMVT079518) that was not included by Gilman (2015), and a collection from 1917 mentioned by Pease in his book (ASP 17087; The New England Botanical Club Herbarium [NEBC] 00754933; Pease 1964). This Pease specimen is currently cataloged as Chamaesyce glyptosperma (Engelm.) Small, which accounts for Angelo and Boufford (2014) noting that no voucher was known for E. serpillifolia in New England. However, we believe that Pease was correct in his identification, based on leaf serrations more typical of E. serpillifolia. The population in Vermont was confirmed as Euphorbia serpillifolia by Nathan Taylor. Approximately 20 plants were observed in August 2018, in an area of ~15 3 20 m. The population has spread from a