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..
Similar to the preceding species and perhaps hybridizing with it where the two grow together; stem stout, tomentose-pubescent, usually branched, 2°-3 1/2° high, leafy to the top. Leaves broadly lanceolate, acute, acuminate or some of them obtusish at the apex, subcordate, rounded, or the upper narrowed at the base, puberulent or glabrous above, pubescent, at least on the veins beneath, 3'-5' long, £'-2' wide; petioles usually stout and short; flowers similar to those of A. incarnata, but the corolla commonly lighter red or pink, rarely white; peduncles and pedicels tomentose; fruiting pedicels erect or incurved; follicles erect, densely pubescent, 2'-3' long.
Glabrous throughout; stem stout, simple or sometimes branched above, 2°- 4° high, leafy to the top. Leaves thick, sessile, or on petioles less than 1" long, oblong or ovate-oblong, usually obtuse and mucronulate at the apex, subcordate, rounded or slightly clasping at the base, 4'-6' long, 1 1/2-3' wide, the primary nerves very wide-spreading; umbels terminal and sometimes also in the upper axils, many-flowered; peduncles shorter than the leaves; corolla-segments oval-oblong, 5"- 6" long, purplish; column very short and thick; hoods oval, obtuse or truncate, gibbous at each side near the base, longer than the anthers and the subulate incurved horn; follicles erect, glabrous, 3-4' long, usually with blunt processes near the apex.
In moist soil, southern Ontario to Ohio, Minnesota, Nebraska, Missouri and Kansas. July-Sept.
Asclepias obtusifolia var. latifolia Torr. Ann. Lyc. N. Y. 2: 117. 1826.
Asclepias latifolia Raf. Atl. Journ. 146. 1832-33.
A. Jamesii Torr. Bot. Mex. Bound. Surv. 162. 1859.
Minutely puberulent when young, glabrous when old; stem stout, usually simple, 1°-2 1/2° high, very leafy. Leaves very thick, oval to orbicular, sessile or nearly so, commonly broadly emarginate and mucronulate at the apex and cordate or subcordate at the base, 4'-6' long and nearly as wide, primary nerves very wide-spreading; umbels 2-4, many-flowered, short-peduncled in the upper axils or rarely terminal; pedicels slender, canescent, nearly 1' long; corolla-segments ovate, acute, 4"-6" long, greenish; column short and thick; hoods truncate, about equalling the anthers, the horn projecting from a short crest over the edge of the stigma; follicles erect on deflexed pedicels, ovoid, acutish, 2 - 3' long, about 1' thick.
On dry plains, Nebraska to Colorado, Texas and Arizona. July-Sept.