Plants that are Toxic to Cats

Below is a list of common houseplants that can be harmful or fatal depending on the quantity swallowed. Also, remember that cats who chew plants are exposed to any chemical pesticides or fertilizers that may have been applied directly to the plants or through the soil.
You can prevent your cat from chewing on plants by misting the leaves then sprinkling them with cayenne pepper. You might also want to consider planting a container of grass (regular grass, not the drug) for your cat. If your cats are digging in your pots, go to your local hobby/craft store and buy a few pieces of plastic needlepoint canvas. Trim it to the shape of the pot, cut a slit in it and then a hole in the center for the plant. Rest it on top of the soil and your cat will be unable to dig.
Note that any plant that looks like a variation of grass is likely going to be considered food to a cat, so it's best to keep them in hanging pots well out of reach.
Symptoms of poisoning will range from seizures and foaming at the mouth to vomiting and coma. Immediate medical attention - as soon as you see the cat has eaten a toxic substance (don't wait for symptoms to appear) - is necessary.