THE FOLLOWING PLANTS CAN BE DANGEROUS TO DOGS:

This is only a partial list.

Acocanthera (fruit and flowers)
Amaryllis (bulbs)
Amsinckia -- Tarweed (foliage, seeds)
Anemone -- wildflower (all parts)
Angel Trumpet Tree (flowers and leaves)
Apple (seeds)
Apricot (pits, inner seed)
Atropa Belladona (all parts, especially black berries)
Autumn Crocus (bulbs)
Avocado (foilage
Azalea (all parts)
Balsam pear (seeds, outer rind of fruit)
Baneberry (berries, roots, foliage)
Beach Pea (all parts)
Betel Nut Palm (all parts)
Belladonna (all parts)
Bird of paradise (seeds)
Bittersweet (berries)
Black locust (bark, sprouts, foliage)
Bleeding Heart (foliage, roots)
Bluebonnet (all parts)
Bluegreen Algae (some forms are toxic)
Bloodroot (all parts)
Bottlebrush (flowers)
Boxwood (all parts)
Buckeye Horse Chestnut (sprouts, nuts)
Buckthorn (fruit, bark)
Buttercup (sap, bulbs)
Calla lily (all parts)
Caladium (all parts)
Cardinal Flower (all parts)
Carolina Jessamine (foliage, flowers, sap)
Cassava (roots)
Castor bean (oil, beans, leaves)
Chalice vine -- Trumpet vine (all parts)
Cherry tree (bark, twigs, leaves, pits)
Cherry Laurel (foliage, flowers)
Chinaberry tree (berries)
Christmas Berry (berries)
Christmast Cactus (sap)
Christmas candle (all parts)
Christmas Rose (foliage, flowers)
Columbine (foliage, flowers, seeds)
Common Privet (foliage, berries)
Coral plant (all parts)
Crocus (bulbs)
Croton (foliage, shoots)
Cyclamen (foliage, stems, flowers)
Daffodil (bulbs, foliage, flowers,pods)
Daphne (berries)
Datura -- Jimsonweed (berries, leaves, seeds)
Deadly amanita (all parts)
Deadly nightshade (all parts)
Death camas (all parts)
Death cap mushroom (all parts)
Dephinium (all parts)
Deiffenbachia -- Dumb cane (leaves)
Destroying Angel -- Death cap (all parts)
Dogwood -- (fruit)
Dutchman's Breeches (foliage, roots)
Eggplant (all parts but fruit)
Elderberry (foliage)
Elephant's ear -- Taro (leaves, stem)
English ivy (berries, leaves)
Equisetum (all parts)
Euphorbia -- Spurges (foliage, flowers, sap)
False Hellebore (all parts)
False henbane (all parts)
Fiddleneck -- Senecio (all parts)
Fly Agaric -- Amanita (all parts)
Four O'Clock (all parts)
Foxglove (leaves, seeds)
Gelsemium (all parts)
Ghostweed (all parts)
Golden chain -- Laburnum (all parts, especially seeds)
Hemlock (all parts, especially roots and seeds)
Henbane (seeds)
Holly -- English and American (berries)
Horse Chestnut (nuts, twigs)
Horsetail Reed -- Equisetum (all parts)
Hyacinth (bulbs)
Hydrangea (flower buds)
Indian turnip -- Jack-in-the-pulpit (all parts)
Impatiens -- Touch-me-not (all parts)
Iris (bulbs)
Ivy -- all forms (foliage, fruit)
Jasmine (foliage, flowers, sap)
Jasmine star (foliage, flowers)
Jatropha (seeds, sap)
Java bean (uncooked bean)
Jerusalem cherry (berries)
Jessamine (berries)
Jimsonweed (foliage, flowers, seed pods)
Johnson grass (all parts)
Juniper (needles, stems, berries)
Laburnum (all parts)
Lambkill -- Sheep laurel (all parts)
Lantana (foliage, flowers, immature berries)
Larkspur (all parts)
Laurel (all parts)
Lily of the valley (All parts, including water they have been kept in)
Lima bean -- Java bean (uncooked bean)
Lobelia (all parts)
Locoweed (all parts)
Lords and ladies -- Cuckoopint (all parts)
Lupine (foliage, pods, seeds)
Machineel (all parts)
Marijuana (leaves)
Mayapple (all parts, except fruit)
Mescal bean (all parts)
Milkweed (foliage)
Mistletoe (berries)
Moccasin flower (foliage, flowers)
Mock orange (fruit)
Monkshood (leaves, flowers, roots)
Morning glory (all parts)
Mountain laurel (leaves, shoots)
Mushrooms -- most wild forms (caps, stems)
Narcissus (bulbs)
Natal cherry (berries, foliage)
Nectarine (seeds, inner pit)
Nicotine bush (foliage, flowers)
Nightshades (berries, leaves)
Oak (acorns, leaves)
Oleander (all parts)
Peach (fruit pit)
Pear (seeds)
Pennyroyal (foliage, flowers)
Peony (foliage, flowers)
Periwinkle (all parts)
Philodendron (leaves, stems)
Pikeweed (leaves, roots, immature berries)
Plum (foliage, inner seed)
Poinsetta (leaves, flowers)
Poison hemlock (foliage, seeds)
Poison ivy (sap)
Poison oak (foliage, fruit, sap)
Poison sumac (foliage, fruit, sap)
Pokewood -- Poke cherry (roots, fruit)
Poppy (all parts)
Potato plant (new shoots, eyes)
Privet (all parts)
Redwood (resinoids, leached wet wood)
Rhododendron (all parts)
Rhubarb (leaves, uncooked stems)
Rosary peas (seeds, flowers, pods)
Rosemary (foliage in some species)
Russian thistle (foliage, flowers)
Sage (foliage in some species)
Salmonberry (foliage, fruit)
Scarlet pimpernel (foliage, flowers, fruit)
Scotch broom (seeds)
Senecio -- Fiddleneck (all parts)
Skunk cabbage (all parts)
Snapdragon (foliage, flowers)
Snowdrop (all parts, especially buds)
Snow on the mountain -- Ghostweed (all parts)
Spanish bayonet (foliage, flowers)
Sudan grass (all parts)
Star of Bethlehem (foliage, flowers)
Sundew (foliage)
Sweet pea (seeds and fruit)
Tansy (foliage, flowers)
Taro -- Elephant's ear (foliage)
Tarweed (foliage, seeds)
Thornapple (flowers, foliage, pods)
Tiger lilly (foliage, flowers, seed pods)
Toad flax (foliage)
Tobacco (leaves)
Tomato plant (foliage, vines)
Touch-me-not (all parts)
Toyon berry (berries)
Trillium (foliage)
Trumpet vine (all parts)
Venus flytrap (all parts)
Verbena (foliage, flowers)
Virginia creeper (sap)
Water hemlock (roots, foliage)
Wildflower (leaves, flowers)
Wild parsnip (rootes, foliage)
Wisteria (all parts)
Yam bean (roots, immature pods)
Yellow star thistle (foliage, flowers)
Yew (American, English, Japanese) (needles, seeds)

Source: http://www.petstation.com