Yes, Milkweed is toxic to dogs!
Dogs accidentally consuming the Milkweed plants can show the following clinical symptoms: Vomiting, Prolonged Depression, Incoordination, Hypersalivaton, Sleepiness Or Excitation, Dilated Pupils, Low Body Temperature, Low Blood Pressure, Coma, Seizure And Death (In Rare Cases).
Milkweed consumption is also toxic to Cats and Horses.
Toxic Principles Of Milkweed: Some species contain cardiotoxins (steroidal glycosidic cardenolides) and other species contain neurotoxins..
More Info About The Milkweed Plant
Scientific Name: Asclepias species
Family: Asclepiadaceae.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.