These plants can be harmful to kids and pets
Angel Trumpet (all of the plant) Hyacinth (bulb)
Azalea (all) Iris (all)
Bittersweet (leaves, fruit) Jerusalem Cherry (leaves and unripe fruit)
Buckhorn (all) Lily of the Valley (all) 
Caladium (all) Mistletoe (all)
Castor Bean (all) Mushrooms (all of certain types)
Chinese Lantern (all) Narcissus (all)
Chrysanthemum (all) Nightshade (all)
Creeping Charlie (all) Oleander (all)
Daffodil (all) Peony (roots)
Delphinium (all) Philodendron (all)
English Ivy (all) Potato (sprouts, vines, unripe tubers)
Foxglove (leaf, seeds) Rhododendron (all)
Gladiola (bulb) Rhubarb (roots, leaves)
Holly (all) Trumpet Lily (all)
Horse Chestnut (flower, sprout, and seeds) Vinca Vine (all)

Plant Toxicity
Insoluble Oxalates (refer to table) mucosal inflammation, salivation, pawing at mouth, vomiting, diarrhea rinse mouth w/water or milk
+/- induce vomiting
Soluble Oxalates (refer to table) convulsions, tremors, cardiac, drinking or urinating excessively induce vomiting, hospitalization
Grayanotoxin Plants
(rhododendron, mountain laurel, Jaranese pieris)
vomiting, diarrhea, CNS, depression, weakness, seizures, increased heart rate induce vomiting, very toxic, hospitalization
Toxalbumin Plants (castor bean, mole bean, castor oil) vomiting, diarrhea, systemic signs seeds very toxic, induce vomiting
(daffodil, tulip, hyacinth, iris)
vomiting, diarrhea, seizures induce vomiting
Cycads (false sago palm) vomiting, salivation, red gums, depression, excessive drinking seeds very toxic, induce vomiting, hospitalize
Liliaceae (Easter lily, tiger lily, day lily) minor GI upset induce vomiting
Marijuana unsteady, vomiting, CNS, depression more harmful if dry, induce vomiting
Onion (garlic, chives, onion) hemolysis, bloody urine, anemia, weakness, jaundice 5.5 gm of dry onion/kg can cause hemolysis and anemia
induce vomiting, hospitalize