Yes, Lord-and-Ladies is toxic to dogs!
Dogs accidentally consuming the Lord-and-Ladies 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).
Lord-and-Ladies consumption is also toxic to Cats and Horses.
Toxic Principles Of Lord-and-Ladies: Insoluble calcium oxalates.
More Info About The Lord-and-Ladies Plant
Scientific Name: Arum maculatum
Family: Araceae.
Also known as: Arum, Wake Robin, Adam-and-Eve, Starch Root, Bobbins, Cuckoo Plant.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.