Flower:

Flowers are about 1/3 inch across and ½ to ¾ inch long with rich purple petals contrasted with a smooth rose/pink hood and horns. The 5 petals fall away freely, tips angled down with an open waist between petal base and hood base. The 5 hoods are short and thick, not extending half their length above flower center. Horns are long and narrow, appressed down into flower center and overlaping each other's tips. Clusters are convex, 2½ to 3 inches wide with up to 20 flowers each, at the top of the plant and 2 or more arising from upper leaf axils.

Leaves and stem:

 Leaves are 1½ to 3 inches wide, 4 to 6 inches long, narrowly egg-shaped to oblong, opposite, toothless, hairless, slightly heart-shaped at the base with little to no leaf stalk or somewhat clasping the stem, and are mostly upswept, revealing the creamy colored or reddish midvein from underneath. The side veins on the leaf surface are all connected and do not extend to the edge of the leaf, creating a border effect all around the edge. Stems are hairless, sturdy, single and unbranched.

Notes:

Another rare Minnesota milkweed, its historical range has always been limited to our southern central counties. Some websites claim it can be grown quite easily on richer garden soils but I have no first hand experience with this at home. There are several pink to purplish milkweeds with opposite, generally oval leaves. A distinguishing feature of Sullivant's Milkweed is its overall hairlessness—other species have hairy leaves and/or stems. All Asclepias were formerly in family Asclepiadaceae but have been reassigned to Apocynaceae (Dogbane).