Common Milkweed

Common Name – Common Milkweed, Butterfly flower, Silkweed, Silky Swallow-wort, Virginia Silkweed – The plant exudes milky-white latex when the stems or leaves are severed.

Scientific Name – Asclepias syriaca – The generic name is the god of healing and medicine in Greek mythology and was assigned to convey the various medicinal properties attributed to the plant. The species name means ‘from Syria.’ This is probably a case of mistaken identity. The milkweed closely resembles a plant of the genus Apocynum, commonly known as dogbane, which is found in Asia Minor.

Potpourri: The common milkweed is a botanical contradiction. It is a weed – a successful colonizer of waste areas; however, it is also a viable crop with a panorama of practical uses including insulation, rubber and rope, to say nothing of its sweet aroma and generally pleasant appearance. It is a poison with a potency that merits a warning in every field guide; however it is also one of the many edible wild plants lauded for savor and nutrition. It is one of the more notable medicines of the Native Americans, some of whom applied it to their arrows for its toxicity. It is shunned by grazing animals for its acrid taste; however it is the sine qua non food source for many insects, not the least of which is larvae of the iconic monarch butterfly, which are protected by the milkweed’s poisons from their own predators. It is widely considered to be the singular plant with the greatest potential for exploitation that has escaped the agricultural combine of the commercial food and drug industries. It is still an honest and simple weed, implied by the wholesomeness of milk. Milkweed’s got milk.

Milkweed was one of the first plants identified by the earliest colonists of North America. The first depiction of the plant was provided by John White, a member of the 1585 colonial expedition to Roanoke sponsored by Sir Walter Raleigh. He was the governor of the subsequent “Lost Colony” established in 1587 and the grandfather of Virginia Dare, the first English child born in North America. His drawing of the milkweed is captioned “The herbe which the savages call Wysauke wherewith theie cure their wounds which they received by the poisoned arroes of their enemyes.” The drawing was given to John Gerard, the noted English herbalist and author of the seminal tome The Herball or General Historie of Plants, who was coincidentally a financial backer of the Roanoke expedition. He included the plant in the 1597 edition of The Herball under the title of Indian Swallow-woort: “There growth in that part of Virginia, or Norembega, where our English men dwelled (intending to erect there a colony) a kind of Asclepias, or Swallow-woort, which the savages call Wisnanck.” He noted the copious quantities of silk that it produced, and, in keeping with the zeitgeist of the time offered the following observation: “…beholde the justice of God, that as he hath shut up those people and nations in infidelitie and nakedness; so hath he not as yet given them understanding to cover their nakedness … notwithstanding that the earth is covered over with this silke … which were sufficient to apparel many kingdoms if they were more carefully manured and cherished.” He recommended that the plant be called Virginia silkweed, apparently with no knowledge of the milky latex exudate. The name milkweed was first used by the American botanist Jacob Bigelow in 1814.

The milkweed plant is the type species for the milkweed family – Asclepiadaceae – consisting of over 250 genera and 2,000 species worldwide; the genus Asclepias has 140 species worldwide of which 108 are in North America. The milkweed family is comprised of plants with two shared characteristics: the aforementioned milky latex exudation and an idiosyncratic method of pollination. The male anthers generate fertilizing pollen in specialized sacs called pollinium that are configured in horseshoe-shaped pairs. As the plodding pollinator proceeds along the flower petal in pursuit of the nectar cynosure, slits in between the petals are configured to promote the distension of one leg in order to hook onto the horseshoe pollinium for transport to the female style of the next flower. The process must be repeated with some exactitude at the destination to succeed; pollen inserted backwards fail to successfully germinate. The evolutionary purpose for this burdensome cross pollination process is unclear, as it impedes rather than enhances the probability of fertilization (most plants rely on a simple pollen dusting of an insect’s hairy legs). The paucity of milkweed pods on each plant relative to the ubiquity of the flowers attests to this observation.

The relative rarity of the pods is offset by their fecundity – each producing hundreds of seeds – and by their mode of transport – windborne on pappi of diaphanous silk-like filaments. The evolution of these seed bearing filaments favored a waxy covering to prevent water absorption and a hollow structure to enhance wind-borne distribution. Light weight and waterproof are key attributes for insulation materials. Prior to World War II, the seed fibers from the kapok tree (Ceiba pentandra) which grows primarily in south Asia, were used for the insulation in life jackets. The disruption of ocean going trade due to wartime hostilities motivated the identification of milkweed as an alternative; over 20 million pounds of milkweed fiber were used in the manufacture of over one million life vests. A number of studies of milkweed as an alternative to goose down in insulated clothing and bedding have been conducted over the last decade. While goose down is superior in terms of compressibility and loftiness (a textile term for full-bodied, firm and resilient), it is expensive at over $100 per pound. A pound of milkweed floss requires about 100 pods; a one acre plot of milkweed will produce about 100 pounds of floss. The economics of milkweed floss (it is a weed after all) relative to goose down (geese need food and shelter) makes it a compelling alternative.

The legion of medicinal properties attributed to milkweed is probably related to its general toxicity; moderate levels of which can have palliative effects by deterring pests and predators. Various types of milkweed were extensively used by Native American tribes for a wide variety of conditions, primarily those that required some form of purging – as an emetic to induce vomiting, as a cathartic to stimulate bowel movement, and as a diuretic to increase urine flow. The roots were boiled to make a tea that was used as an expectorant and to induce sweating; the milky latex was used topically to treat warts and as a vulnerary bandage, taking advantage of the coagulation of the sticky white exudate when exposed to air. The Mohawks reportedly used it with Jack-in-the-Pulpit as an antifertility drug; Hopi women allegedly used it to stimulate the flow of breast milk. The widespread use of milkweed by Indians was adopted by colonists as a part of the folk medicine practices of that era. The English herbalist Nicolas Culpeper established the precedent for milkweed as medicine with his publication of The Complete Herbal in 1653 in which he characterizes it as having a “faculty against all poisons … and are effectively given to such as are bitten by any venomous beast or stung by any serpent or other creature” and “taken also in wine against the plague and pestilence.” The combinations of nativist uses and Culpeper’s encomiums resulted in the inclusion of Asclepias syriaca in the United States Pharmacopoeia from 1820 to 1882 as a treatment for constipation and for application to bee stings, cuts and warts, though there were many other “off label” uses. The choice of Asclepius as the genus name is testimony to the purported healing benefits of milkweed. Asclepius was the Greek god of medicine – the namesake god of numerous healing temples in ancient Greece; among his daughters were Hygieia, the goddess of sanitation and health, and Panacea, the goddess of universal cures. His somewhat counterintuitive symbol, the rod of Asclepius, consists of a staff with a serpent entwined. It is the basis for the symbol used to characterize the medical profession to this day, not the frequently mistaken caduceus, the dual serpent staff of Hermes (who was a messenger and not a healer). It remains unclear why a serpent was chosen as the symbol for healing, though theories abound. Of all of the possible plants that Linnaeus could have honored with the assignation of the Greek god of healing, he chose milkweed, testimony to its alleged panacean properties.

Milkweed’s complex chemistry is reflected in the species specific associations that it has with animals – it is food for some and distasteful and best and poisonous at worst for others. The latex contains what are broadly called cardiac glycosides, enzymes that promote the contraction of the heart muscle which could be used to offset arrhythmia and heart attack (though there is no indication that it has ever been used for this). The bitter principles alpha and beta asclepiaden that are found in chemical analyses of the latex give rise to the bitter taste that is anathema to larger grazing mammals and birds, but which is attractive to insects that employ it to prevent being eaten by these same animals. In addition to Monarch caterpillars, milkweed beetles (Tetraopes tetraophtalmus), the large and small milkweed bugs (Oncopeltus fasciatus and Lygaeus kalmii respectively) and the milkweed leaf beetle (Labidomera clivicollis) all feed on milkweed. All of these insects advertise their toxicity aposematically, their Halloween orange and black colors a visible warning to predators that, if eaten once, they will not be eaten again. And, last but not least, milkweed plants can be eaten by Homo sapiens, not to render them distasteful to predators, but rather to provide nutrition. However, they can only be made edible by boiling – not once but two or three times disposing of the water after each cycle – in order to rid them of their bitterness. This is not all that uncommon in plant and fungi cooking, as bitter principles are often volatile, and are thus evaporated in the cooking process. Young sprouts up to eight inches high can be gathered and cooked as something like a wild asparagus. The flowers and leaves are reputed to be something of a delicacy. Even the pods are edible if gathered early enough, an okra-like entrée without the gooiness of Cajun cuisine. Bon appétit.