Creeping Bellflower (Campanula rapunculoides)
A European garden flower escaped from cultivation, often in yards of older homes where it had originally been planted. This plant grew at the edge of a sidewalk in Beechview in the shadow of a tall hedge.
From Gray’s Manual: C. RAPUNCULOIDES L. Stems slender, 6-10 dm. high, smoothish, or finely pubescent above; lower leaves long-petioled, cordate-ovate ; the upper ovate-lanceolate, short-petioled to sessile, irregularly serrate-dentate, hispidulous beneath; flowers nodding, single in the axils of bracts, forming racemes; calyx and capsule scabrous-puberulent; corolla campanulate, 2-3 cm. long; capsule opening by pores at base. Roadsides, thickets, etc., e. Que. to Ont., 0., and s. N. Y. July, Aug. (Introd. from Eurasia.) Var. UCRANICA (Bess.) C. Koch. Smoother; the calyx and capsule essentially glabrous. Similar situations, Que. and N. E. (Introd. from Russia.)
Although Gray says it blooms in July and August, this plant was part of a colony happily blooming in early October.