Showy milkweed-Asclepias speciosa Torr.-Poisonous plant

Showy milkweed

General poisoning notes:

Showy milkweed (Asclepias speciosa) is a native plant found in dry rangelands in western Canada. The plant is poisonous to sheep and cattle. However, this plant is so distasteful to livestock that they ingest it only under extreme circumstances (Fleming et al. 1920)


A stout, sparingly branched, pubescent perennial, 1 1/2-3 ft. tall, with large, oval, blue-green leaves and showy, spherical clusters of rose-colored flowers. Flowers occur at the top of the stem and on stalks from leaf axils. A grayish, velvety plant with erect leafy stems and with umbels of star-like pinkish flowers in upper axils and at top. Sap milky.


Scientific Name: Asclepias speciosa Torr.
Vernacular name(s): showy milkweed
Scientific family name: Asclepiadaceae
Vernacular family name: milkweed

Geographic Information

Alberta, British Columbia, Manitoba, Saskatchewan.

Notes on Poisonous plant parts:

Experimental feeding tests on sheep showed that leaves are poisonous, but that large amounts must be ingested: (a 43-kg ewe died after ingesting 1 kg of green leaves. The pods and seeds are also poisonous (Fleming et al. 1920).

Toxic parts:

Leaves, mature fruit, seeds.

Toxic plant chemicals:

Desglucosyrioside, syrioside.

Animals/Human Poisoning:

Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.



General symptoms of poisoning:

appetite, loss of
breathing, labored
breathing with grunts

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