Prairie dogbane, Apocyn chanvrin

Apocynum cannabinum var. glaberrimum A. de Candolle; A. cannabinum var. hypericifolium (Aiton) A. Gray; A. cannabinum var. pubescens (R. Brown) A. de Candolle; A. cordigerum Greene; A. hypericifolium Aiton; A. hypericifolium var. cordigerum (Greene) Béguinot & Belosersky; A. leuconeuron Greene; A. missouriense Greene; A. sibiricum Jacquin var. cordigerum (Greene) Fernald

Herbs 3–10 dm. Stems glabrous or eglandular-pubescent. Leaves spreading to ascending; petiole 2–7 mm, often absent on lower leaves, glabrous or sparsely pubescent; blade ovate to lanceolate, 3–8(–11) × (0.4–)1.5–4 cm, mostly more than 2.5 times as long as wide, membranous, base rounded, cuneate, or auriculate, margins weakly to strongly revolute, apex acute to rounded or obtuse, usually apiculate, surfaces glabrous or densely eglandular-pubescent abaxially, glabrous or sparsely eglandular-pubescent adaxially. Inflorescences usually not exceeding foliage; peduncle 1–3.5 cm, glabrous or sparsely pubescent. Pedicels 2–3 mm, glabrous. Flowers: calyx lobes triangular-ovate to lanceolate, 1–2 × 0.3–0.8 mm, glabrous or infrequently pubescent; corolla white, greenish white, or yellowish white, glabrous abaxially and adaxially, tube 1.5–2.5 × 1.5–2 mm, ± as long as or slightly longer than calyx lobes, lobes erect or spreading, triangular-ovate, 1.5–2 × 0.7–1.2 mm. Follicles (40–)120–200 × 2–3 mm. Seeds 3.5–6 × 0.5–0.8 mm. 2n = 16, 22.

Flowering summer–fall; fruiting summer–fall. For­ests, woodlands, fields, lakeshores, margins of swamps, rocky or gravelly river margins, dry creek beds, road­sides, railroad rights-of-way, other disturbed sites; 10–2500 m; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., Que., Sask.; Ala., Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico (Baja California, Chihuahua, Coahuila, Nuevo León, Tamaulipas).

Some American authors have treated plants with ses­sile or short-petiolate, lower cauline leaves and auric­ulate blades as Apocynum sibiricum Jacquin; these plants are here included in A. cannabinum.

Fiber derived from the stems of Apocynum cannabinum has long been considered to be of much higher quality than that of the other Apocynum species (S. Cheatham et al. 1995).