Yes, Mum is toxic to dogs!
Dogs accidentally consuming the Mum 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).
Mum consumption is also toxic to Cats and Horses.
Toxic Principles Of Mum: Sesquiterpene, lactones, pyrethrins and other potential irritants.
More Info About The Mum Plant
Scientific Name: Chrysanthemum spp.
Family: Compositae.
Also known as: Chrysanthemum, Daisy.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.