Interesting Botanical Finds in Exeter, New Hampshire

On September 5, 2019, a naturalized occurrence of Achillea filipendulina Lam. was discovered near downtown Exeter, New Hampshire, growing on String Bridge (42.9817828N, 70.9455468W). String Bridge crosses the freshwater Exeter River just meters upstream of where the river abruptly becomes tidal and its name changes to the Squamscott River. A single plant with three fruiting stems and one flowering stem was growing out of the cement holding together stonework on the outer, east side of the bridge (Figure 1). Associates included Eutrochium dubium (Willd. ex Poir.) E. E. Lamont, Lythrum salicaria L., and Poa compressa L. This occurrence may have originated from seed in some nearby garden that washed down and was deposited in the cement crack. This is only the second known naturalized location for A. filipendulina in New England (Consortium of Northeastern Herbaria 2019); Frank C. Seymour collected a specimen in 1969 from a naturalized population in clay soil at Mill Pond, Benson, Vermont. A voucher specimen of A. filipendulina from String Bridge was collected and will be deposited at Hodgdon Herbarium (NHA), University of New Hampshire (Nichols NHB-753). Nearby in Exeter on the same date, Odontites vulgaris Moench was found growing on a town-owned dike (42.9863958N, 70.9506048W) that forms a stormwater diversion basin (Clemson Holding Pond) adjacent to the Squamscott River (Figure 2). The dike was owned by the adjacent mills (built in 1827) long before the town took ownership (P. Vlasich, Exeter Town Engineer, pers. comm.). Over 100 plants were scattered on either side of a path along the entire length of the dike (440 meters) in poor dry soil. Odontites vulgaris, an introduced annual native to Europe and Asia, is hemiparasitic on the roots of grass and herb species. The most frequent grasses on the dike were Digitaria ischaemum (Schreb.) Muhl., D. sanguinalis (L.) Scop., Eragrostis frankii C. A. Mey. ex Steud., E. spectabilis (Pursh) Steud., Poa compressa L., Schizachyrium scoparium (Michx.) Nash, and Sporobolus vaginiflorus