Smooth shadbush, amélanchier glabre
Trees or shrubs. Stems 1–15, 2–17 m, solitary or in small clumps. fastigiate; twigs glabrous at flowering. Leaves conduplicate in bud; at least half-expanded and unfolding, usually conspicuously reddish, glabrous or with a few evanescent hairs by flowering; petioles 12–25 mm; blades abaxially green, elliptic to ovate oblong or obovate, 4–6 x 2.5–4 cm, firm, bases subcordate or rounded, margins serrate nearly to or to base with 6–8 teeth per cm, lateral veins 12–17 pairs, anastomosing and becoming indistinct near margins, apices acute to acuminate, surfaces glabrous. Inflorescences 4–11-flowered, usually drooping, 3–7 cm, only proximalmost 1–2 pedicels subtended by leaf. Pedicels glabrous, proximalmost 1.5–3 cm. Flowers: hypanthia campanulate, 2.5–5 mm diam.; sepals recurving after flowering , 2–5 mm, adaxially hairy; petals white, linear-oblong, 10–20 x 3–7 mm, not andropetalous; stamens 20; styles 5; ovary summits rounded, glabrous. Pomes dark purple, (4–)10–15 mm diam., sweet. 2n = 34, 68.
Flowering Apr–Jun; fruiting Jun–Jul.
Dry to moist deciduous, mixed, and less frequently, coniferous forests , fields, thickets, roadsides; 0–2000 m
St. Pierre and Miquelon; N.B., Nfld. & Labr. (Nfld.), N.S., Ont., P.E.I., Que.; Ala. , Conn., Del., D.C., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va., Wis.
(see Systematics page for references cited)
Amelanchier laevis is common through much of its range and readily identified by its tree size, leaves that are reddish and glabrous by flowering, and long inflorescences, pedicels, and petals. It grows chiefly at high elevations in the southeastern United States. The relationship to its closest relative, A. arborea, is discussed under the latter.
Amelanchier laevis frequently hybridizes with other members of the genus, including A. arborea, A. bartramiana, A. canadensis, A. humilis, A. interior, A. spicata, and A. sanguinea (M. L. Fernald 1950; L. Cinq-Mars 1971, WEber and Campbell 1989). J. E. Cruise (1964) documented hybrid swarms between A. laevis and both A. arborea and A. canadensis in New Jersey. The hybrid with A. bartramiana, A. x\neglecta Eggleston, can usually be found when these two species grow together (Weber and Campbell 1987). The hybrid with A. arborea, A. x\grandiflora Rehder, is used ornamentally.
A. C. Dibble et al. (1998) concluded that Amelanchier laevis is possibly one of the parents of A. “rubra”, an entity that is morphologically distinct but that Dibble et al. did not name as a new species because of insufficient information about its geographic range and reproductive status. This microspecies is a tetraploid, cespitose shrub with stems to 3.5 m, leaves that are reddish and glabrous at flowering, and petals that are often faintly reddish and slightly twisted. The ovary summit is mostly sparsely pubescent, but may also be densely lanuginose or glabrous. Our quantitative analysis places A. “rubra” in an intermediate position between the cluster of A. laevis plus A. intermedia on the one hand and A. nantucketensis or A. spicata on the other. It is possible that A. “rubra” could be a hybrid with one of each of these arborescent species (A. laevis and A. intermedia) plus one of the shrub species (A. nantucketensis and A. spicata). We have located numerous populations of A. “rubra” on Mount Desert Island and eastward for about 120 km along the Maine coast. We resist publishing A. “rubra” as a new species because we do not know that it is independently reproductive. All four species that we hypothesized could have been parents of this entity grow throughout the range of A. “rubra”, and its occurrences could be from repeated hybridization rather than reproduction on its own. We have observed plants that appear to be F1s of A. “rubra” and later-generation hybrids with A. bartramiana as one of the parents. This situation highlights some of the taxonomic challenges in this genus.
Amelanchier laevis has been documented to be self-compatible and to produce seeds asexually (C. S. Campbell et al. 1985; A. C. Dibble et al. 1998).