Asclepiadaceae, Milkweed Family
Shrub to 10 feet tall and 4 feet wide
Sonoran and Mojave Deserts; southeastern California, southwestern Arizona and Baja California, Mexico
Dry slopes and washes, Creosote Bush Scrub
Living Desert Location:
Upper Colorado Garden, Nature Trail
White-stemmed Milkweed possesses a stark beauty, with its pale stems reaching skyward from the varnished desert foothills.
This is the tallest milkweed of the southwest deserts, with a few stems arising from a woody base. The chalky-white, erect stems appear succulent and contain copious amounts of latex. In spring, the tips of the rush-like stems bloom with white flower clusters which may be tinged with purple or brown.
Numerous insects are attracted to the flowers, including butterflies and parasitic wasps, particularly the large Tarantula Hawk (Pepsis thisbe). White-stemmed Milkweed is a host plant to Monarch and Queen Butterflies, whose caterpillars feed upon the stems. It is said the latex consumed by the caterpillars make the adult butterflies unpalatable to predators.
The fruit is an elongated, tapered seed pod, or follicle, with wispy tufts attached to the seeds, aiding in wind dispersal. White-stemmed Milkweed can be found in some of the most arid environments with few, if any, other shrubs tolerating the same harsh surroundings in which it grows.