These are very toxic to cats. If they swallow even the tiniest amount, they can suffer severe kidney damage.
The whole plant is poisonous to pets, but the seeds cause the most damage. If an animal eats even one seed they can have vomiting, diarrhea, seizures, liver failure and depression.
Specifically, the bulb of tulips is harmful. The toxins in tulip buds can cause pets to develop gastrointestinal problems, drooling, loss of appetite, convulsions, depression of the central nervous system and cardiac issues.
The Rhododendron species have substances that will cause vomiting, drooling, diarrhea, weakness and depression of the central nervous system for pets.
All parts of this plant can cause G.I. tract issues, heart problems, hypothermia and sometimes death.
Castor Bean has ricin, which will cause severe stomach pain, vomiting, diarrhea, excessive thirst, weakness and loss of appetite.
The root of cyclamen is the most toxic. It causes G.I. irritation and vomiting. A few cases of pet poisoning from cyclamen have even led to death.
Kalanchoe can affect cardiac rhythm and rate and can cause G.I. issues.