Yes, Lavender is toxic to dogs!
Dogs accidentally consuming the Lavender 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).
Lavender consumption is also toxic to Cats and Horses.
Toxic Principles Of Lavender: Linlool, linalyl acetate.
More Info About The Lavender Plant
Scientific Name: Lavendula angustifolia
Family: Lamiaceae.
Also known as: Common Lavender, English Lavender.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.