Leaves of asclepias asperula
are narrow, triangular to lance-shaped, and, like the light-green stems, have a covering of fine hairs, including along the margins. They are crossed by a thick, light-colored mid vein and much thinner side veins. Leaves tend to fold upwards from the central vein to varying degrees, and they are held at right angles to the stem.
The inflorescence is a spherical cluster of small flowers, each consisting of five green petals, curving inwards, enclosing a pentagonal structure (the crown) of purple, white-tipped projections around a greenish center, which includes five fused stamens. Clusters are about 3 inches in diameter, and contain around 20 flowers. Plants may produce one stem, or as many as 15, each topped by one cluster. The fruit is a conical pod, occurring in pairs and resembling the horns of an antelope, hence the alternative common name.