Yes, Tarragon is toxic to dogs!
Dogs accidentally consuming the Tarragon 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).
Tarragon consumption is also toxic to Cats and Horses.
Toxic Principles Of Tarragon: Essential Oils.
More Info About The Tarragon Plant
Scientific Name: Artemisia dracunculus
Family: Asteraceae.
Also known as: French Tarragon, Estragon.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.