The Beautiful Milkweeds

Enlarge Image Image Gallery Butterfly weed, the most vivid of all the milkweeds Photograph by J. G. Strauch, Jr.

That old standby definition of a weed—any plant growing where it’s not wanted—doesn’t always apply in the world of herbs. Their usefulness and sometimes neglected beauty make them welcome guests despite their eagerness to run unchecked through the garden.

Never has there been a more attractive and useful group of weeds than the milkweeds, more than 100 species belonging to the genus Asclepias and distributed mainly throughout North America and parts of southern Africa. Most are straight-stemmed herbaceous perennials, but a few are shrubs that may grow 12 feet tall. The leaves vary from impressively large, broad, and woolly to threadlike and smooth. They may be arranged on the stem in opposite pairs, alternately, or in tight whorls. A few desert species are virtually leafless. The New Mexico herbalist Michael Moore has described them as “truly weird . . . smooth sticks stuck unceremoniously in the sand”, a simple utilitarian design for a harsh environment.

The numerous, showy, and often scented flowers are usually borne in clusters called cymes, either at the ends of the stems or in the leaf axils. They are ingeniously adapted to pollination by insects. At the top of every flower is a crown of five pouches, or hoods, each containing an enticing stash of nectar. As an insect alights on a flower, its legs are guided down into grooves, where one of its hairs or claws catches on a structure connecting two waxy masses of pollen called pollinia. The insect flies off to another flower, then browses among its hoods for nectar and dislodges the pollinia, which then pollinate the second flower.

Flowers that get pollinated produce large, spindle-shaped seedpods. Some species have silky smooth pods; others, warty or spiny ones. Inside each pod are numerous seeds, each with a tuft of long, silky hairs. When the pods split open, the hairs act as little parachutes. Anyone who has played with milkweed pods as a child remembers the silky down and the gently rising seeds. In the words of the botanist Charles Millspaugh in his book Me­-di­cinal Plants (1892):

Balanced by the pendant seeds, they mount gracefully to immense heights, whence they are wafted far and wide by the lightest zephyr until, dampen­ed by dew or rain, they fall.

The name “milkweed” comes from the milky latex that exudes when a milkweed plant is wounded. Contact with the latex irritates the skin of some people, but it benefits the plant by deterring munching by herbivorous animals. Attempts to produce synthetic crude oil from this latex have proven ­unsuccessful.

Milkweeds As Medicine

The generic name Asclepias honors Asklepios, the Greek god of medicine, so highly did Native Americans and ­European settlers value milkweeds as medicine. Millspaugh (who apparently was enamored of the genus) summed up the manifold uses of one species, A. tuberosa, known to gardeners as butterfly weed but to herbalists as pleurisy root: