Zizotes milkweed

Zizotes milkweed is a small plant with one to seven stems that usually are unbranched, but occasionally may branch near the base. Each stem is 10 to 50 centimeters (4–20 in) long and spread outward from the crown or rest upon the ground. The stems are somewhat to very thickly covered in curving hairs. It is a perennial plant with a rhizome, a modified underground stem. The leaves are attached to opposite sides of the stems, or nearly so, and are egg shaped in outline, somewhat rectangular with rounded corners, or a rounded triangle. They measure 4–11 cm (1.5–4.5 in) long and 1.2–6.5 cm (0.5–2.5 in) wide and sometimes have a somewhat wavy edge. The inflorescences are umbel, having all the flower stalks attached together at one point resembling the ribs of an umbrella, with the umbels low down on the stems attached by a peduncle and those high up attaching directly to the stem or nearly so. The five petals of each flower are fused at their bases and the lobes are greenish-white. Flowering can start as early as February, though usually not until March, and can occur as late as November.

Zizotes milkweed is native to North America from the Colorado and Louisiana in the United States to Costa Rica. In Central America it is native to every country except for Belize and Panama. It is widespread in Mexico, growing in 24 of the 36 states. In the United States it is found in Arizona, New Mexico, Colorado, Oklahoma, Texas, and Louisiana. It is widespread in Texas, especially in the southern half of the state. In New Mexico it is much less common, only being recorded in Chaves, Santa Fe, and San Miguel counties. Likewise it is recorded in just Blaine and Major counties in Oklahoma. In the three other US states it is found in just one county in each, Jefferson Parish, Louisiana, Las Animas County, Colorado, and Cochise County, Arizona.

In the southern United States zizotes milkweed is an important host species for the monarch butterfly alongside Asclepias viridis and Asclepias asperula.