This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Perennial branching herbs, with opposite entire leaves, and small white or pink flowers in terminal and sometimes axillary corymbed cymes. Calyx 5-parted, the segments acute. Corolla urceolate to campanulate, the tube bearing within 5 small appendages alternate with the stamens, the limb 5-lobed. Stamens inserted on the base of the corolla; anthers sagittate, connivent around the stigma and slightly adherent to it. Disk 5-lobed. Ovary of 2 carpels; ovules numerous in each carpel; stigma ovoid, obtuse, obscurely 2-lobed. Follicles slender, elongated, terete. Seeds numerous, small, tipped with a long coma. [Greek, dogbane.]
About 11 species, of the north temperate zone, most abundant in North America. Type species: Apocynum androsaemifolium L. Corolla campanulate, not angled, 4"- 41/2" long, pink, its lobes widely spreading or recurved.
1. A. androsaemifolium.
Corolla urceolate to short-tubular, or narrowly campanulate, angled, 11/2"- 31/2" long, greenish, white, or faintly pink, its lobes a little spreading, or erect. Corolla narrowly campanulate, 2 1/2"- 3 1/2" long, lobes nearly equal the tube.
2. A. medium.
Corolla urceolate to short-tubular, 1 1/2"- 3" long, lobes much shorter than the tube. Calyx-lobes ovate, much shorter than the corolla tube.
Calyx-lobes lanceolate, about as long as the corolla-tube. Leaves and cymes glabrous, or sparingly pubescent.
Leaves all narrowed at the base and distinctly petioled; flowers greenish; plant rather bright green.
4. A. cannabinum.
At least the lower leaves sessile, and mostly rounded or subcordate at the base; plant pale glaucous green; flowers white.
5. A. sibiricum.
Leaves, cymes, and often the whole plant densely pubescent.
6. A. pubescens.
Apocynum androsaemifolium L. Sp. Pl. 213. 1753. Syst. Ed. 10, 946. 1759.
A. divergens Greene, Leaflets 1: 56. 1904. .
Rootstock horizontal; stem 1°- 4° high; branches broadly spreading, mostly glabrous. Leaves ovate or oval, acute or obtuse and mucronate at the apex, rounded or narrowed at the base, glabrous above, pale and usually more or less pubescent beneath, 2'- 4' long, l'- 2 1/2' wide; petioles 2"-4" long; cymes loose; pedicels 2"-3" long, subulate-bracted at the base; flowers about 4" broad; calyx-segments shorter than the tube of the pinkish corolla; corolla-lobes revolute; follicles about 4' long, narrowed at the apex.
In fields and thickets, Anticosti to British Columbia, south to Georgia, Missouri, Nebraska and Arizona. Ascends to 3500 ft. in Virginia. Honey-bloom. Bitter-root or -dogbane. Rheumatism-wood. Wild ipecac. Wandering milk-weed. Western wall-flower. Fly-trap. June-July. Linnaeus inadvertently failed to affix a binominal specific name in the first edition of his "Species Plantarum," but corrected this six years later.