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..
Asclepias verticillata L. Sp. Pl. 217. 1753. .
Roots slender, fascicled; stem slender, simple or branched, pubescent in lines above, leafy, 1°- 2 1/2° high. Leaves narrowly linear, sessile, verticillate in 3's-7's or some of them alternate, glabrous or very nearly so, their margins narrowly revolute; umbels numerous, many-flowered; peduncles slender, 1/2' - 1 1/2' long; pedicels almost filiform, shorter than the peduncles; corolla greenish white, its segments oblong, 1 1/2"- 2" long; column about i" high; hoods white, oval, entire, about equalling the anthers, much shorter than the subulate incurved horn; follicles erect on the erect fruiting pedicels, narrowly spindle-shaped, glabrous, 2' - 3' long.
In dry fields and on hills, Maine and southern Ontario to Saskatchewan, south to Florida, Mexico and New Mexico. July-Sept.
Asclepias galioides H.B.K. Nov. Gen. 3: 188. 1818.
Glabrous, except the minutely pubescent stems and pedicels. Stems erect, 1° high or more, from a horizontal root-stock; leaves erect or spreading, in whorls of 2-6, narrow!; linear, 2'-3' long, the margins revolute; peduncles longer than the pedicels and shorter than the leaves; umbels 9' - 13' in diameter; flowers greenish-white; corolla-segments 2" long; hoods as high as the anthers, broadly rounded at the summit, dorsally hastate-sagittate, the ventral margins slightly involute, entire; horn arising from the base of the hood, long-exserted over the anthers; anther-wings minutely notched at the base; follicles erect on erect fruiting pedicels, attenuated, 2' - 2 3/4' long, glabrous or minutely puberulent.
Kansas to Colorado, Arizona and Mexico. May-July.
Stems 4'-10' high, tufted from a woody root. Leaves very numerous, crowded, sometimes obscurely whorled, filiform-linear, 1'--2'. long, smooth or minutely roughened, the margins revolute; umbels 2-several, short-peduncled, few-flowered; pedicels filiform, puberulent, . 3"-4" long; corolla greenish white, its segments oblong, 1 1/2" - 2" long; column short; hoods white, erect, oblong, entire, equalling the anthers, shorter than the slender incurved horn; follicles erect on erect fruiting pedicels, narrowly spindle-shaped, 1 1/2' - 3' long, finely puberulent.
Dry plains, Iowa to South Dakota. Arkansas, Texas, Wyoming, Colorado and New Mexico.