Local nurseries sell many common landscape plants that can be poisonous to pets. To add insult to injury, plants don’t come with a toxic warning label.
The level of toxicity will depend on the plant, the part of the plant  and  amount ingested, along with your pet’s current health. Not every animal will eat a toxic plant but some pets are simply more curious than others. If you want to err on the side of caution, here are some plants that you may want to avoid entirely or put in areas of your garden that are off limits to nibbling pets.

Lilies (Lilium sp.) are considered to be highly toxic to cats and can result in severe kidney damage even if small amounts are ingested.
Sago Palm (Cycas Revoluta) all parts of this palm are poisonous, but the seeds contain the greatest amount of toxin.  Just one or two ingested seeds can have serious effects including vomiting, diarrhea, seizures and liver failure.
Azalea/Rhododendron (Rhododenron sp.) contains grayantoxins which can produce vomiting, diarrhea, weakness and if severe enough, ultimately lead to coma and death from cardiovascular collapse.
Oleander (Nerium oleander) all parts of the plant are considered to be toxic, as they contain cardiac glycosides that can have serious effects like gastrointestinal tract irritation, abnormal heart function, hypothermia and even death.
Yew (Taxus sp.) contains a toxic substance known as taxine, which affects the central nervous system causing trembling, lack of coordination and difficulty breathing. It can also cause gastrointestinal irritation and cardiac failure.
Daphne (Daphne sp.) is prized for its scented flowers but all parts of the plant are poisonous and just a few berries could kill an animal.
Lantana (Lantana sp.) berries contain high levels of toxins if ingested while they are still green, causing vomiting, diarrhea, labored breathing, and weakness.
English Ivy (Hedera helix) contains triterpenoid saponins that can result in vomiting, abdominal pain, drooling and diarrhea.

Plants are not the only danger in the garden. Keeping your pet away from insecticides (used in the garden to kill insects), herbicides (for killing weeds) and rodenticides (rat bait) is not really difficult if you take an organic approach to gardening. By working with Mother Nature, not against her, you’ll find a healthy eco-system that is happy to coexist with you and your pets.
Lastly, be aware of what type of mulch you bring into your dogscape. Cocoa mulch, a byproduct of chocolate production, contains the same toxic compounds as chocolate, which is poisonous to dogs. Coir or Coconut Husk mulch is known for its ability to retain water around water loving plants. However, this same expansion will occur in a dog’s digestive track if ingested and potentially cause blockage in the intestines.
Even with the best prevention strategies, accidents can happen. If your pet exhibits any of the following signs of poisoning, contact your vet for immediate assistance: digestive trouble (vomiting, diarrhea, loss of appetite), neuromuscular injury (seizure, paralysis, labored breathing), confusion, excessive tear production or rashes.
For an extensive list of toxic plants for dogs and cats, visit the ASPCA’s website at www.aspca.org
Animal Poison Control Center’s hotline is available 24 hours a day (for a small fee)  to help pet owners with potential poisoning questions (888) 426-4435