Information sources on toxic and non toxic plants
ASPCA list of plants that are toxic to dogs and non toxic to dogs The American Society for the Prevention of Cruelty to Animals has a mission, as stated by founder Henry Bergh in 1866, is "to provide effective means for the prevention of cruelty to animals throughout the United States."
Dog's Trust factsheet of poisonous plants, garden and household substances
The household poisons list is worth a read, as are the labels on many cleaning products.
Example: We spread a small amount of fish, blood and bone meal around our roses and raked it into the soil. Max was attracted by the smell and started to eat the the traces of fertiliser (and some soil as well!). We have not used this on the accessible garden since and now feed our roses with liquid feed.
Example: Max was suffering from a yellow discharge from his eyes which would not go away even when treated with ointment from the Vet. We finally tracked down the source of the problem to chemicals in the floor cleaning fluid. We now clean the hard floors with a dilute solution of water and white vinegar which has eliminated the problem.
Gardeners World most toxic plants
Gardeners World 12 tips for a Dog-Friendly Garden
Kennel Club list of common poisonous plants
More Than Insurance (RSA Group) toxic plants More Than sponsored the Poisonous Pawtanical Garden display at the Horniman Museum
PDSA list of poisonous plants
Pet Owners Association poisonous plants list
Woodland Trust Poisonous Plants