The following is a list of potentially toxic plants

Acokanthera - all parts toxic, except ripe fruit
Amaryllis
Angel's Trumpet - leaves seed and flowers
Apricot - pits, leaves and bark
Apple - seeds, leaves, bark
Avocado - unripe fruit, and stems
Azalea
Balsam Pear, Bitter Melon
Baneberry
Belladonna
Bird of Paradise - seed pods and flowers
Bittersweet
Black Locust
Boxwood
Bracken Fern
Buckthorn
Burdock
Buttercup
Caladium
Calla Lily
Catclaw Acacia - twigs and leaves
Caster Bean
Cherry - pits, leaves and bark
Chinaberry
Clematis
Coral Plant
Crocus
Cycad or Sago Cycas
Daffodil
Daphne
Death Camas
Delphinium
Devil's Ivy
Dieffenbachia (dumb cane)
Eggplant - unripe/overripe fruit, leaves
Elderberry - roots, leaves, stems, bark
Elephant's Ears or Taro
Euonymus - filit, bark, leaves
European Pennyroyal
Figs
Four o'clock
Foxglove
Heliotrope
Henbane
Holly - leaves, berries
Horse Chestnut
Horse Nettle
Hyacinth
Hydrangea
Iris
Ivy (Boston, English; some others)
Jack-in-the-Pulpit
Jerusalem Cherry
Jessamine Yellow
Jimsonweed - leaves, seeds and flowers
Jonquil
Juniper
Kalanchoe
Lantana
Larkspur
Laurel
Lily-of-the-Valley
Lobelia
Locoweed
Lupine
Marijuana
Milkweed
Mistletoe
Moonseed
Monkshood
Morning Glory - seeds
Mushrooms
Narcissus
Oak
Oleander
Peach - leaves, pit, bark
Pear - leaves, seeds, bark
Peony
Periwinkle
Peyote
Philodendron
Pigweed
Plum - leaves, pit, bark
Poison Hemlock
Poison Ivy
Poison Oak
Poison Sumac
Poinsettia
Poppy
Pokeweed
Potato - sprouts, leaves, berries, green tubers
Pothos
Primrose
Ragwort
Red Maple
Rhododendron
Rhubarb - leaves
Rosary Pea
Sage
Shamrock Plant
Skunk Cabbage
Snowdrop
Sorrel
Spurges
Star of Bethlehem
Sweet Pea
Tobacco
Tomato - stems and leaves
Tulip
Virginia Creeper
Vetches
Water Hemlock
Waxberry
Wisteria
Yew

(Taken from Bird Talk magazine – October 1997 issue)