Stems of apocynum cannabinum
are colored green or red, and bear pairs of large, broad leaves at regular intervals, from the base all the way to the top. The leaves have a prominent white or cream-colored center vein, and alternating side veins. The leaf length is around three times the width. Stem leaves are sessile, while those near the base have a short stalk. Stems and leaves are usually hairless. Leaf pairs are rotated around the stem relative to those above and below. Leaves are angled horizontally outwards, or are slightly ascending.
Flowers are produced in flat-topped clusters at the top of the stems; they have a green, five-lobed calyx and a white or pale pink corolla, about twice as long as the calyx. The five corolla lobes tend not to open fully, typically angled between 0 and 90 degrees from the vertical. Fruits are long (up to 7 inches), slightly curved, downwards-hanging pods, initially green, later red.Apocynum androsaemifolium
is a similar species which has pink rather than white flowers, longer corollas, and broader leaves.