General poisoning notes for Asclepias syriaca

Common milkweed (Asclepias syriaca) is a native perennial herb found in eastern Canada in fields, ditches, and waste places. This plant has poisoned sheep in the eastern United States. The plant contains cardiac glycosides, which are toxic to animals (Reynard and Norton, Joubert 1989).

Asclepias syriaca . . COMMON MILKWEED

2 to 5 ft. . . Sun to lt. shade . . Avg. soil . . Native . . Large, but somewhat dull, purplish-pink flower heads. Summer. The wide, smooth leaves are 4 to 9 inches long. A very important host plant for the Monarch Butterfly. . . #1312 . . Zones est. 4 to 8 . . . .

The eastern two-thirds of North Dakota is home to common milkweed. Elsewhere, the species ranges from Maine to Manitoba, south to Georgia and Texas.

Like many of our milkweeds, common milkweed is perennial from a deeply buried rhizome. The stout stems are usually solitary, covered with short, fine hairs, and, when severed, exude copious amounts of milky latex. Plants can be up to six feet tall, but North Dakota specimens are usually only about half that height. The opposite leaves are up to 4 inches wide and 8 inches long and covered with fine white hairs, especially below. From one to three inflorescences, each bearing 20 to 100 or more rose- to purplish-white flowers are borne on stalks (peduncles) that arise from the upper leaf axils. At maturity, the specialized fruits, termed follicles by botanists, are up to four inches long and 1-1/2 inches thick. Inside these usually warted, pod-like structures are large seeds bearing white hairs nearly two inches long.

Look for common milkweed from June through August on native prairie, roadsides, and most other open habitats that are not heavily grazed by livestock. Domestic livestock has been poisoned by milkweeds, but all milkweeds are distasteful to livestock, and losses occur only when animals are forced to eat these plants. Common milkweed has a long history of use as human food. The young shoots and well-filled follicles of this plant are edible if boiled with one or two changes of water. These were a staple of many Amerindian tribes and thought to be cultivated by some. The dried latex was chewed. The roots were used for various diseases of the lungs and thorax and were listed in the U. S. Pharmacopeia in the late 1800s. The follicles were also gathered during World War II for their fluffy seeds that substituted for kapok in emergency flotation devices.

Most of the roughly 2,400 species in the milkweed family (Asclepiadaceae after Asklepios, the Greek god of medicine) are found in Africa and tropical America. Most of the roughly 100 species in the genus Asclepias are found in America. The Swedish father of modern plant taxomony, Carl von Linne (Linneaeus) described common milkweed for science in the mid-1700s. He erroneously assigned the plant the specific epithet syriaca because he thought that the type specimens had been carried to Europe from the Orient, rather than from eastern North America. But we are stuck with this misnomer, because in botany, a name first used to describe a valid species is unchangeable, regardless of errors in derivation or spelling.

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