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)

References:

Fleming, C. E., Peterson, N. F., Miller, M. R., Vawter, L. R., Wright, L. H. 1920. The narrow-leaved milkweed and the broad-leaved or showy milkweed. Plants poisonous to livestock in Nevada. Univ. Nev. Agric. Exp. Stn. Bull., 99. 32 pp.

Nomenclature:

Scientific Name: Asclepias speciosa Torr.

Vernacular name(s): showy milkweed

Scientific family name: Asclepiadaceae

Vernacular family name: milkweed

Go to ITIS*^ca for more taxonomic information on: Asclepias speciosa

References:

Agriculture Quebec. 1975. Noms des maladies des plantes du Canada/ Names of plant diseases in Canada. , Quebec City, Que., Canada. 288 pp.

Alex, J. F., Cayouette, R., Mulligan, G. A. 1980. Common and botanical names of weeds in Canada/Noms populaire et scientifiques des plantes nuisibles du Canada. Revised. Agric. Can. Publ., Ottawa, Ont., Canada. 132 pp.

Bailey, L. H., Bailey, E. Z. 1976. Hortus third. Revised. MacMillan, New York, N.Y., USA. 1290 pp.

Scoggan, H. J. 1978, 1979. The flora of Canada. Nat. Mus. Nat. Sci. (Ottawa) Publ. Bot. 7(1)-7(4). 1711 pp.

Van Wijk, H. L. 1911. A dictionary of plant names. Martinus Nijhoff, The Hague, The Netherlands. 1444 pp.

Victorin, M. 1964. Flore Laurentienne. 2nd ed. Univ. Montreal, Montreal, Que., Canada. 952 pp.

Geographic Information

Alberta
British Columbia
Manitoba
Saskatchewan

References:

Bailey, L. H., Bailey, E. Z. 1976. Hortus third. Revised. MacMillan, New York, N.Y., USA. 1290 pp.

Boivin, B. 1966, 1967. Énumération des plantes du Canada. Provencheria 6. Nat. Can. (Que.) 93: 253-274; 371-437; 583-646; 989-1063. 94: 131-157; 471-528; 625-655.

Image or illustration

showy milkweed:

Images: images.google.com

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

References:

Fleming, C. E., Peterson, N. F., Miller, M. R., Vawter, L. R., Wright, L. H. 1920. The narrow-leaved milkweed and the broad-leaved or showy milkweed. Plants poisonous to livestock in Nevada. Univ. Nev. Agric. Exp. Stn. Bull., 99. 32 pp.

Toxic plant chemicals:

desglucosyrioside
syrioside

References:

Joubert, J. P. 1989. Cardiac glycosides. Pages 61-97 in Cheeke, P. R., ed. Toxicants of plant origin. Vol. II. Glycosides. CRC Press, Inc., Boca Raton, Fla., USA. 277 pp.

Animals/Human Poisoning:

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

Cattle

Sheep

General symptoms of poisoning:

appetite, loss of
breathing, labored
breathing with grunts
recumbency

References:

Fleming, C. E., Peterson, N. F., Miller, M. R., Vawter, L. R., Wright, L. H. 1920. The narrow-leaved milkweed and the broad-leaved or showy milkweed. Plants poisonous to livestock in Nevada. Univ. Nev. Agric. Exp. Stn. Bull., 99. 32 pp.