Most people with at least some knowledge of plants recognize one or more kinds of milkweeds. Virtually all parts of the United States and Mexico have one or more kinds, recognizable by a combination of milky sap, seed pods, and parachuted seeds. Various species live in our Chihuahuan Desert Region, one of the most spectacular inhabiting the higher mountains. The brilliant orange to red flowers of the Butterfly Milkweed virtually scream "Beauty"!
At lower elevations, several species tend to be overlooked because they
don't fit our prejudices as to what a proper milkweed should look like. Instead of
rather sturdy, erect plants, they are twining vines, either trailing across the ground
or climbing on desert shrubs. Nonetheless, a careful look will show all of the milkweed
features. Regardless of habit, many are toxic or highly distasteful to most animals.
The Monarch Butterfly takes advantage of this—its caterpillars feed on the foliage,
incorporating some of the chemical compounds in their bodies. A bird feeding on the
resulting butterfly is pretty sure to never sample the nasty things again!
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.