10 Plants that are Poisonous to Dogs

This was on mnn (Mother Nature Network) and is rather long but if you're a dog lover like me, its important to have this info.

1. Grapes -- The toxicity of grapes to dogs was once thought to be an urban legend, but it's true; even a small serving can cause vomiting and diarrhea, while larger amounts can lead to kidney failure. Researchers aren't yet sure what exactly causes this reaction, whether pesticides or a fungal toxin.
And while keeping the grapes and raisins in your pantry away from your dog is a concern, you should be on the lookout for grapevines outside as well. As any dog owner knows, berries and fruits of all sorts are a tempting treat.
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2. Mushrooms -- While there are plenty of great-tasting, perfectly safe mushrooms out there, dogs just don't seem capable of discerning the difference between the edible and the toxic. To be on the safe side, it's best not to allow dogs to eat any wild mushrooms at all, unless you can confidently identify the species yourself.
Amanita, Galerina and Lepiota species are especially dangerous because they contain toxins that cause a series of worsening symptoms, from vomiting to swelling in the brain. Amanita phalloides, the Death Cap mushroom, is responsible for most of the reported fatal mushroom poisoning cases in dogs.
3. Marijuana -- For most people, the likelihood of your pet gaining access to marijuana -- whether on a live plant or not -- is relatively low. But regardless of your view of marijuana's safety for human use, it has absolutely no benefits for your pet.
After ingesting marijuana, a dog can experience symptoms like slow heart rate, lack of coordination, disorientation, drooling and tremors that can persist for up to three days.
4. Lilies -- While lilies are well-known as a serious danger to cats, certain varieties are highly toxic to dogs as well.
The peace lily, calla lily, amaryllis, lily of the valley, autumn crocus and the common houseplant, giant Dracaena or palm lily, are all deemed dangerous to dogs by the ASPCA. Ingestion of lilies can cause gastrointestinal upset, depression, anorexia and tremors.
5. Black walnuts -- Dropping from black walnut trees by the thousands, the nuts themselves don't contain anything that can harm your dog.
But once they start to decompose, they grow molds that can cause tremors and seizures. If you have one of these trees in your yard and your dog seems attracted to the nuts, it might be a good idea to rake them up on a regular basis.
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6. Sago palm -- Often used in landscaping and as houseplants, sago palms develop seed pods that are often very tempting to dogs.
Unfortunately, the whole plant and the seeds in particular contain a potent toxin called cycasin that can be fatal, even if the dog only eats a single seed. Ingestion of any part or amount of this plant warrants immediate emergency treatment.
7. Azalea -- A member of the widely toxic genus rhododendron, the azalea is found in many varieties all over the United States and is commonly used as an ornamental flowering shrub in landscaping.
Ingestion of just a few leaves can cause serious issues like digestive upset, drooling, loss of appetite, weakness and leg paralysis. In some cases, eating azalea can lead to coma or death.
8. Castor bean -- This ornamental tropical plant, also used as a crop for castor oil, contains the toxic protein ricin.
At the least, eating this plant can burn a dog's mouth and throat and lead to excessive thirst, vomiting and diarrhea. But ingestion of even an ounce of seeds can be lethal.
9. Daffodils -- Among the first blooms to herald the arrival of spring, daffodils are a cheerful addition to the garden, but they contain poisonous alkaloids that can cause vomiting, excessive salivation, diarrhea, convulsions, tremors and heart problems.
The bulbs are the most dangerous part of the plant. Other common names for the daffodil include narcissus, jonquil and paper white.
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10. Dieffenbachia (Dumb Cane) -- With its broad variegated leaves, the dieffenbachia is often recommended as an ideal houseplant for natural air purification.

But if you choose to have one in your home, be sure it's well out of your dog's reach. When eaten, it not only burns the mouth and throat but causes the esophagus to swell, potentially blocking the dog's airway.