Many people ask what plants are NOT good for pets. Here is a short list of a few common plants that you may have at home.

Notice the Oleander (specially in the Oleander area), very common here in Bakersfield. It is very toxic to pets if they chew on them.

Alfalfa (Medicago sativa L.)
American Coffee Berry Tree see Kentucky Coffee Tree
Bloodroot (Sanguinaria canadensis L.)
Bouncing Bet (Saponaria officinalis L.)
Bull Nettle (Solanum carolinense L.)
Bracken or Brake Fern (Pteridium aquilinum L.)
Burning Bush see Fireweed
Buttercup (Ranunculus spp.)
Carelessweed see Pigweed
Castor Bean (Ricinus communis L.)
Clover, Alsike & Other Clovers (Trifolium hybridum L. & other species)
Cocklebur (Xanthium strumarium L.)
Creeping Charlie see Ground Ivy
Crown of Thorns (Euphorbia milii)
Curly Dock (Rumex crispus L.)
Daffodil (Narcissus spp.)
Delphinium (Delphinium spp.)
Devil's Trumpet see Jimson Weed
Dogbane (Apocynum spp.)
Dutchman's Breeches (Dicentra cucullaria (L.) Bernh.)
Elderberry (Sambucus canadensis L.)
English Ivy (Hedera helix L.)
Ergot (Claviceps purpurea (Fr.) Tul.)
Fern, Bracken (Pteridium aquilinum L.)
Fireweed (Kochia scoparia L.)
Foxglove (Digitalis purpurea L.)
Ground Ivy (Glecoma hederacea L.)
Hemlock
        Poison (Conium maculatum L.)
        Water (Cicuta maculata L.)
Horse Chestnut, Buckeyes (Aesculus hippocastanum L.)
Horse Nettle (Solanum carolinense L.)
Horsetails (Equisetum arvense L. & other species)
Hyacinth (Hyacinth orientalis)
Hydrangea (Hydrangea spp.)
Ivy
        English (Hedera helix L.)
        Ground (Glecoma hederacea L.)
        Poison (Toxicodendron radicans (L.) Kuntze)
Jack-in-the-Pulpit (Arisaema spp.)
Jamestown Weed see Jimson Weed
Japanese Yew (Taxus cuspidata Sieb. & Zucc.)
Jerusalem Cherry (Solanum pseudocapsicum L.)
Jimson Weed (Datura stramonium L.)
Kentucky Coffee Tree (Gymnocladus dioica (L.) K. Koch)
Kentucky Mahagony Tree see Kentucky Coffee Tree
Klamath Weed see St. Johnswort
Lamb's Quarters (Chenopodium album L.)
Lantana (Lantana camara L.)
Larkspur (Delphinium spp.)
Lily-of-the-Valley (Convallaria majalis)
Lupine (Lupinus spp.)
Mad Apple see Jimson Weed
Maple, Red (Acer rubrum)
Mayapple (Podophyllum peltatum L.)
Milkweed, Common (Asclepias syriaca L.)
Mint, Purple (Perilla frutescens)
Nicker Tree see Kentucky Coffee Tree
Nightshade (Solanum spp.)
Oleander (Nerium oleander L.) very common in Bakersfield
Ohio Buckeye (Aesculus glabra Willd.)
Philodendron (Philodendron spp.)
Pigweed (Amaranthus spp.)
Poison Hemlock (Conium maculatum L.)
Poison Ivy (Toxicodendron radicans (L.) Kuntze)
Poke (Phytolacca americana L.)
Purple Mint (Perilla frutescens)
Redroot see Pigweed
Rhododendron (Rhododendron spp.)
Rhubarb (Rheum rhaponticum L.)
Squirrelcorn (Dicentra canadensis (Goldie) Walp.) see Dutchman's Breeches
Staggerweed (Dicentra spp.) see Dutchman's Breeches
St. Johnswort (Hypericum perforatum L.)
Stink Weed see Jimson Weed
Stump Tree see Kentucky Coffee Tree
Sudan Grass (Sorghum vulgare var. sudanense Hitchc.)
Summer Cypress see Fireweed
Thorn Apple see Jimson Weed
Tulip (Tulipa spp.)
Water Hemlock (Cicuta maculata L.)
White Snakeroot (Eupatorium rugosum Hout.)
Wild Onion (Allium spp.)

Thanks to http://www.library.uiuc.edu