Castorbean
White Snakeroot
Senico (Ragwort)
Water Hemlock
Poison Hemlock
Cockelbur
Pigweed
Jimsonweed
Johnsongrass
Cherry
Yew
Red Maple
Easter Lily (most all lilies and bulbs)
Oleander
Rosary Pea
Moderately toxic include, but are not limited to:
Dumbcane
Bulbs
Lupine
Rhubarb
Azalea
Oats
Fescue
Yellow or White Sweet Clover
Milkweed
Mustards
Nightshades (such as Eggplant)
Spurges
Buckeye/Horsechestnut
Tobacco
Horsetail
Larkspur
Black Walnut
Red Oak
Black Locust
Minimally Toxic:
Catnip (surprising!)
St. Johnswort
English Ivy
Buttercups
Stinging Nettle (not surprising!)
For a complete list you can visit: www.vet.purdue.edu/toxic/bytox1.htm