The following plants are poisonous - either the whole or parts of the plant. Many are used in herbal and homeopathic medicines in small doses. If you are unsure about a plant, do not eat it. A good site for identifying common poisonous plants is: http://www.annwnscauldron.com/apothecary/herbpois/herbpoisa.html
http://en.wikipedia.org/wiki/Main_Page is also helpful, but do not rely on these sources alone when identifying plants for consumption.
Plants marked with * are highly toxic and fatal if eaten. The list is incomplete.
Aconite (wolfsbane, monkshood) Aconitum napellus, Aconitum anthora, Aconitum variegatum (All Aconitum)
Adam and Eve Root Aplectrum hyemale
African Milkbush Synadenium grantii *
Aloe Venenosa Aloe venenosa
Almond (Bitter) Prunus Leaves and pits
Anemone Anemone nemorosa, A. quinquefolia (all Anemone genus)
Anemonella (Windflower) Thalictrum thalictroides
Angel's-trumpet, (Thorn-apple, Indian-apple, Moonflower) Datura inoxia
Apple, Balsam Momordica balsamina
Apple, Bitter Citrullus colocynthis
Apple Seed Malus domestica (consumed in great qty)
Apricot Prunus (Leaves, twigs and seeds ) *
Arnica Root Arnica montana
Arrowgrass Triglochin maritima and T. palustris *
Autumn Crocus (Meadow Saffron) Colchicum autumnale
Azalea Actaea
Baneberry (Bugbane, Herb Christopher) Actaea spicata
Baneberry, Red Actaea rubra
Baneberry, White Actaea pachypoda (Berries)
Bay Tree Laurus Nobilis (Seeds)
Beans, Common, String, French, Red Kidney Phaseolus vulgaris (Raw beans and sprouts - bean seeds must be cooked for at least 10 minutes to destroy toxin)
Bearberries Arctostaphylos (Mildly, in large doses)
Belladonna (see Nightshade) *
Birthwort Aristolochia
Bittersweet (Woody Nightshade) Solanum dulcamara *
Black Cherry (see Wild Cherry) *
Black Hellebore see Hellebore
Black Henbane see Henbane
Black Jetberry Rhodotypos scandens (Fruits) *
Black Locust Robinia pseudoacacia
Black Nightshade see Nightshade
Bloodroot Sanguinaria Candensis *
Blue Dogbane Amsonia tabernaemontana *
Blue Flag Iris versicolor
Bog Rosemary Andromeda polifolia (In large quantities)
Boneset Eupatorium petrolatum, Eupatorium perfoliatum (all Eupatorium genus)
Bottlebrush Buckeye Aesculus parviflora * (All Aesculus species)*
Box Wood Buxus
Bracken Fern Pteridium aquilinum
Broadleaf Dock (Butter Dock) Rumex obtusifolius
Broom Cytisus scoparia
Bryony, Black Tamus communis
Bryony, White Bryonia alba
Buckthorn Rhamnus (Berries, mildly)
Burning-Bush Dictamnus albus
Bush Lily, (Kaffir Lily) Clivia miniata
Buttercup Ranunculus (All ranunculus are poisonous when eaten fresh)
Butterfly weed Asclepias
Cabbage Tree Andira inermis
Calabar Bean Physostigma venenosum
Caladium see Elephant's Ear
California Buckeye Aesculus californica *
Calotropsis Calotropis procera
Calla Lily Calla palustris (Zantedeschia aethiopica) *
Camphor Cinnamonum camphora (Oil, consumed in large quantities)
Canada Moonseed Menispermum canadense *
Carolina jasmine (yellow jessamine) Gelsemium sempervirens
Cassava (manioc) Manihot esculenta *
Castor Bean, Castor Oil Plant Ricinus communis (Seeds) *
Celandine (Lesser) Ranunculus ficaria
Celandine (Greater) C helidonium majus
Cherry Prunus cerasus
Cherry Laurel Prunus laurocerasus, Prunus caroliniana (Leaves, twigs, stems & seeds)*
Chile Pepper Capsicum annuum (In large quantities)
China Berry Melia azedarach
Chokecherry Prunus virginiana (Leaves & seeds)
Clematis Clematis recta
Coastal Leucothoe Leucothoe axillaris *
Coca, Bolivian Erythroxylon Coca
Cocculus, Indicus Anamirta paniculata
Comfrey Root Symphytum officinale
Coral bean Erythrina herbacea
Corn cockle Agrostemma githago
Cowbane (Water Hemlock) Cicuta virosa
Creeping Buttercup Ranunculus repens
Croton Codiaeum variegatum (All Croton family)
Cyclamen Cyclamen (All Cyclamen species)
Daffodil Narcissus
Daphne Daphne striata (All Daphne species - poisonous berries)*
Deadly Nightshade (Belladonna) Atropoa belladona
Death Camas (Black snakeroot, Meadow Deathcamas) Zigadenus venenosus, Z. Gramineus, Z. paniculatus, Z. nuttallii *
Delphinium (Larkspur) Delphinium *
Devil's Trumpet Datura metel
Dock Rumex (uncooked leaves)
Dogbane (Indian Hemp) Apocynum androsaemifolium, A. cannabinum, A. Sibericum (All Apocynaceae)*
Dropwort, Water Hemlock Oenanthe crocata
Dumbcane Dieffenbachia
Elderberry Sambucus (Raw berries)
Elephant Ear Colocasia antiquorum, Alocasia, Caladium (all Caladium species) *
Eucalyptus Eucalyptus (Plant in large quantities, & oil)
Euphorbia see Spurge
Ferns (see Bracken Fern)
Fetterbush Lyonia *
Flax Linum usitatissimum (All parts, in large quantities)
Fly poison Amianthium muscitoxicum
Fool's Parsley Aethusa cynapium
Foxglove Digitalis purpurea *
Frangipani Plumeria (All Plumeria genus)
Giant Elephant Ear Alocasia
Ginkgo Ginkgo Biloba (In large doses)
Globe Flower Trollius europaeus (All Trollius species)
Glory Lily Gloriosa superba *
Goldenseal Hydrastis canadensis
Heliotrope Heliotropium (In large doses)
Hellebore, Black (Christmas rose) Helleborus niger (In large quantities)
Hellebore, False Adonis autumnalis, Adonis vernalis , Veratrum viride
Hellebore, Green (Green false hellebore) Veratrum viride (In large quantities)
Hellebore, White Veratrum album *
Hemlock, Poison Conium maculatum *
Hemlock, Water Cicuta virosa, Cicuta maculata *
Hemp Cannabis Sativa (If eaten in large quantities)
Henbane, Black Hyoscyamus niger *
High John the Conqueror Ipomoea jalapa
Holly (European) Ilex aquifolium (Berries in large quantity)
Holly (American) Ilex Opaca (Berries in large quantity)
Honeysuckle Lonicera (Vine & fruit)
Honeysuckle (Japanese) Lonicera japonica (Berries in large quantities)
Horse Chestnut Aesculus hippocastanum (Seeds, leaves & sprouts) *
Horse Nettle (Carolina horsenettle, Wild tomato) Solanum carolinense *
Hyacinth Hyacinthus orientalis
Hydrangea Hydrangea (All Hydrangea species)
Ignatius Beans Strychnos Ignatii
Iris Iris
Ivy, English Hedera helix
Ivy, Poison Rhus Toxicodendron
Jack-in-the-pulpit (Wake-Robin) Arum triphyllum, Arisaemia triphyllum
Java Bean Cestrum (Raw beans, seeds & roots)*
Jessamine (jasmine) Cestrum nocturnum
Jetbead Rhodotypos tetrapetala
Jerusalem Cherry Solanum pseudocapsicum (Unripe berries & leaves) *
Jimsonweed Datura stramonium
Jonquil Narcissus
Kentucky coffee tree Gymnocladus dioica
Laburnum Cytisus Laburnam, Labunum anagryroides *
Lantana Lantana camara *
Larkspur Consolida, Delphinium nelsonii (All Delphiniums) *
Leopard's bane Arnica montana
Lily (most Liliaceae)
Lily, Atamasco Zephyranthes atamasco *
Lily of the Valley Convallaria majalis
Lily of the Valley bush (Japanese Andromeda) Pieris japonica (Leaves & flowers)*
Lobelia (cardinal flower, Indian tobacco) Lobelia (If eaten in large quantities)
Lovage, Water Cenanthe fistulosa
Laurel (English) Prunus laurocerasus (Leaves, twigs & seeds) *
Leucothoe Leucothoe fontanesiana, L. Axillaris, L. Populifolia *
Locoweed Astragalus and Oxytropis *
Lupin (Lupine) Lupinus (All Lunpinus species)
Manchineel tree Hippomane mancinella
Mandrake (May apple) Podophyllum peltatum
Marsh Marigold Caltha palustris
May Apple Podophyllum peltatum Green parts, unripe fruit, & rhisomes *
Meadow Rue Thalictrum (All Thalictrum Species)
Meadow Saffron see Autumn Crocus *
Mescal Buttons Anhalonium Lewinii
Mescal bean (Texas mountain laurel) Sophora secundiflora, Calia secundiflora
Mexican Tea Chenopodium ambrosioides *
Milkvetch Astragalus
Milkweed Asclepias
Mistletoe Berries Viscum album, Phoradendron
Monkshood (see Aconite, Aconitum)
Morning Glory Ipomoea violacea, I. tricolour
Mountain Andromeda Pieris floribunda (Leaves and flowers)*
Mountain Laurel Kalmia latifolia (All parts) *
Mulberry, Red Morus rubra (Mildly)
Mulberry, White Morus alba (Mildly)
Narcissus see Daffodil
Nightshade Solanum Americanum *
Nightshade, Black Solanum nigrum *
Nightshade, Deadly Atropa belladonna *
Nightshade, Woody Solanum dulcamara *
Nightshade, Yellow Urechites lutea *
Nutmeg Myristica fragrans (In large quantities)
Nux Vomica Strychnos Nux-vomica
Oak Quercus (Acorns and leaves)
Oleander Nerium oleander *
Paris Herb Paris quadrifolia
Pin Cherry Prunus pensylvanica (Leaves, stems, twigs & seeds) *
Plum Prunus Leaves and pits
Poinsettias Euphorbia pulcherrima
Poison arrow plant Acokanthera oblongifolia
Poison Ivy Toxicodendron radicans
Poison Oak Toxicondendron diversilobum
Poison Primrose Primula obconica
Poison Sumac Toxicodendron vernix
Primrose Primula vulgaris
Pasque Flowers Pulsatilla vulgaris (Fresh flowers, plant)
Peach Prunus persica (Leaves, twigs and seeds) *
Pennyroyal Mentha pulegium (oil)
Pepper Vine Ampelopsis
Periwinkle (myrtle, vinca) Vinca
Pernettya Pernettya Gaultheria *
Pheasant's Eye Adonis annua, Adonis autumnalis (all Adonis species)
Philodendron Philodendron In large quantities)
Pittosporum Pittosporum
Pleurisy Root (Butterfly weed) Asclepias tuberosa
Plumeria see Frangipani
Poison Ivy Toxicodendron (all Toxicodendron species)
Poison Oak Toxicodendron diversilobum or Rhus diversiloba
Poison Paxillus Paxillus involutus *
Poison Sumac Toxicodendron vernix or Rhus vernix
Poke, Poke Weed Phytolacca (All parts) *
Poppy, Corn Papaver rhoeas (Most papaver species)
Poppy, Opium Papaver somnifera (If eaten) *
Poppy, White Papaver somniferum
Potato Solanum tuberosum (Raw, old, spoilt, green, & all green parts, sprouts) *
Privet Ligustrum *
Quince Cydonia oblonga (Seeds)
Ragwort, (Ragweed, Tansy Ragwort) Senecio jacobaea *
Ranunculus see Buttercup, Celandine
Rhododendron Rhododendron *
Rhubarb Rheum rhaponticum (Leaves)
Rock poppy (celandyne) Chelidonium majus
Rosary Pea Abrus precatorius *
Rue Ruta graveolens *
Saffron, Meadow Colchicum autumnale
Sago Palm Cycas revoluta (In large quantities)
Schefflera Schefflera
Skunk cabbage Symplocarpus foetidus
Snakeroot, Black Zigadenus *
Snakeroot, White Eupatorium rugosum *
Snowdrops Galanthus nivalis
Solomon's Seal Polygonatum
Spotted Cow Bane Cicuta maculata
Spring adonis Adonis vernalis
Spurges Euphorbias
Spurge Laurel (Daphne) Daphne mezereum
Squill Scilla *
Star of Bethlehem Ornithogalum umbellatum
Stavesacre Delphinium staphisagria
St John's Wort Hypericum
Strophanthus Strophanthus Kombé *
Sun Spurge Euphorbia helioscopia
Swallowwort Cynanchum
Swamp Laurel Kalmia angustifolia *
Sweet Cherry Prunus avium (Leaves, stems, twigs & seeds) *
Sweet pea Lathyrus odoratus (Seeds)
Tansy Tanacetum vulgare (in large quantities)
Thornapple (see Jimsonweed) Datura stramonium
Tobacco Nicotiana tabacum
Tomato Solanum lycopersicum, Lycopersicon esculentum Foliage and vines
Tonka Bean Dipteryx odorata
Tree Tobacco Nicotiana glauca *
Trumpet flower (chalice vine) Solandra grandiflora *S
Tulip Tulipa
Tung Nut Aleurites fordii *
Viper's Bugloss Echium vulgare
Virginia Creeper Parthenocissus quinquefolia (Berries) *
Wahoo (Burning Bush) Euonymus atropurpuraea, E. Europoeus (Fruit, seed & bark)
Wake Robin Arum triphyllum (all arum genus)
Water Dropwort Oenanthe aquatica
Water Parsnip Sium latifolium
White Snakeroot Ageratina altissima,
Wild Cherry (Black Cherry) Prunus serotina (Leaves, stems twigs, seeds) *
Winter Aconite Eranthis hyemalis
Wisteria Wisteria
Wolfsbane see Aconitum
Wormwood Artemisia absinthium (In large quantities)
Yellow Allamanda Allamanda cathartica
Yellow Jasmine, False Jasmine, Wild Woodbine Gelsemium nitidum *
Yellow Jessamine Gelsemium sempervirens, G. rankinii *
Yellow Oleander (tiger apple) Thevetia peruviana
Yesterday-today-and-tomorrow Brunfelsia
Yew Taxus baccata (Bark, leaves, seeds) *
Yohimbe Bark Yohimbine (if taken in large amounts)