This list is the second of a two part blog. This list is from the ASPCA website, where more plants are listed. I've included the more popular plants here on this list. Please refer to the ASPCA website for further information.

Rhubarb - Can cause vomiting, and salivation. The leaves and roots are toxic to everyone, including you.
Poison Hemlock - Can cause agitation, tremors, drooling, diarrhea, paralysis and death.
Poison Parsnip (also known as cowbane) - Can cause diarrhea, seizures, tremors, extreme stomach pain, dilated pupils, fever, bloat, respiratory depression and death.
Ragwort (or Tansy) - Can cause liver failure, weight loss, weakness, lack of coordination and neurological problems.
Rhododendron - Can cause vomiting, diarrhea, hypersalivation, weakness, coma, hypotension, cardiovascular collapse and death. Only eating a few leaves can cause serious issues.
Skunk Cabbage - Can cause oral irritation, pain and swelling of the mouth, tongue and lips, excessive drooling, vomiting and difficulty swallowing.
Sorrel - If eaten in large quantities can cause weakness, muscle fasciculations, and potential seizures.
Vinca - Vomiting, diarrhea, low blood pressure, depression, tremors, seizures, coma and death.
When in doubt, you can go to the ASPCA's website and select Animal Poison Control. The ASPCA also has an app that you can download called ASPCA Animal Poison Control Center (APCC).