Chelone obliqua var. erwiniae
Bartonia 10: 19. 1929.
Leaves: midcauline blade (60–) 80–197 mm. Flowers: caly× lobe margins not or sparsely ciliate; corolla: abaxial lobes 12–15 (–16) mm; staminode (6–) 8–12 (–14) mm. 2n = 56.
Phenology: Flowering Jul–Oct.
Habitat: Along streams, marshes, swamps, seeps, springs, wet meadows and woods, pond and lake margins.
Elevation: 1000–1700 m.
Variety erwiniae is considered vulnerable to extinction in the Blue Ridge Province; threats to populations have not been assessed (NatureServe, www.natureserve.org/explorer). N. E. Stamp (1987) identified two common larval seed predators, Endothenia herbesana and Phytomyza cheloniae, which were observed to attack 25% of the capsules from a population and destroy 21% of its seeds. Insect defoliation prior to development of inflorescences reduces floral and seed output significantly in Chelone obliqua var. erwiniae and C. glabra (Stamp 1984). Severe herbivory after flower buds appeared caused decreased seed output, and plants that were defoliated twice in one year often produced no flowers (Stamp 1984). Because of severe levels of herbivory and seed predation observed in var. erwiniae, it may reproduce via seed infrequently, relying on clonal reproduction by rhizomes (Stamp 1987).