Field Guide to Plants Poisonous to Livestock: Western U.S.

Asclepias speciosa

Common name: Showy milkweed
Family: Milkweed
Region: U.S.
Habitat: Waste places, ditch banks, streamsides
Toxic season: Year-round
Features: Erect grayish-green plant up to 5' tall containing milky juice. Leaves are opposite, oval, toothless, leathery, hairy, up to 5" long with prominent midrib. Flowers are pink or light purple, 5-petaled with petals extending outward and arranged in showy, umbrella-like clusters at the ends of plant stems. Seeds are hairy and tufted in pod-like fruits.
Poison type: Cardiac glycosides
Signs/effects: Staggering, depression, weakness, collapse, dilated pupils, elevated temperature, intestinal irritation, rapid heart rate, labored breathing, coma, death. Signs may occur up to 2 days after ingestion of toxic/lethal amount.
Treatment: Treatment most effective if begun early. Activated charcoal, electrolytes, purgatives may reduce absorption and promote excretion (gastrotomy/rumenotomy early after ingestion may also be effective). Keep animal calm.
Comments: All parts toxic, fresh or dry. Unpalatable, but may become more palatable when dry and mixed in hay. Toxic and lethal amounts may be nearly identical at <0.05-2.0% of body weight. Cases of poisoning of all livestock except llamas and alpacas have been reported; the latter two species also may be susceptible.

© Copyright 1998 by Shirley A. Weathers