Toxic Plants by Degree of Toxicity

Extremely Toxic
Castorbean
White Snakeroot
Senecio, Ragwort
Water Hemlock
Poison Hemlock
Cocklebur
Pigweed
Jimsonweed
Johnsongrass
Cherry
Yew
Red Maple
Easter Lily
Oleander
Rosary Pea

Moderately Toxic
Dumbcane (Aroid Family)
Bulbs
Lupine
Rhubarb
Azalea, Rhododendron
Oats
Ergot
Fescue
Yellow, White Sweetclover
Tobacco
Larkspur
Brackenfern
Green False Hellebore
Milkweed
Horsetail
Mustards
Spurges
Nightshades
Buckeye, Horsechestnut
Black Walnut
Red Oak
Black Locust

Minimally Toxic
Foxtail Barley
Common Burdock
English Ivy
Catnip
Poinsettia, Christmas Plant
Tansy
Alsike Clover
Jack-in-the-Pulpit
Dutchman's Breeches
Buttercups
Stinging Nettle
Marijuana
St. Johnswort
Star of Bethlehem
Pokeweed
Bouncing Bet