Common Poisonous Plants of Western Washington Which Affect Livestock*
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Common Name/
Scientific Name
Plant Type Part of Plant Degree of toxicity Poisonous Compound Cumulative? Livestock effects**
Arrowgrass (Triglochin maritima) All Can be severe Glycosides (produce cyanide) Under some conditions can cause illness & death in livestock.
Baneberry (Actaea rubra) Forb All, esp. roots & berries Moderate – Severe Protoamemonin and probably a glycoside or essential oil Stomach cramps, dizziness, vomiting, circulatory failure, headache. European species have caused death.
Bleeding-heart (Dicentra spp.) Forb All Mild – Moderate Alkaloids Trembling, agitation, heavy salivation, vomiting, diarrhea, convulsions, difficult breathing.
Boxwood (Buxus sempervirens) Shrub All Moderate – Severe Steroidal alkaloids (buxine) Abdominal pains, vomiting, diarrhea. Large doses can cause convulsions, coma & death.
Bracken Fern (Pteridium aquilinum) Fern All Mild – Severe Thiaminase enzyme, carcinogens , often glycosides (prunasin) Yes Thiamine deficiency, which can be fatal. Cumulative effects may include cancer. Poisonous compounds can pass into milk.
Buttercups (Ranunculus spp.) Forb All Mild – Moderate Protoanemonin from ranunculin glycoside Inflammation and blistering of skin, gastrointestinal irritation. Usually only present in fresh plants, not dried.
Camas, Death (Zigadenus venenosus) Forb All Severe Steroidal glycosidal alkaloid Salivation, weakness, respiratory difficulty, nausea, convulsions, coma, death.
Cherry, Choke (Prunus virginiana) Tree Seeds, leaves, bark Moderate – Severe Cyanogenic glycoside (produces cyanide) Initial rapid breathing followed by slow, difficult breathing, anxiety, excitement, confusion, headache, vomiting, dizziness, can cause death. Other related species which may be poisonous include mountain ash (Sorbus spp.), Hawthornes (Crataegus spp.), Pyracantha, Cotoneaster
Clematis (Clematis spp.) Vine All Mild – Moderate Protoanemonin from ranunculin glycoside Inflammation and blistering of skin, gastrointestinal irritation. Usually only present in fresh plants, not dried.
Cocklebur (Xanthium strumarium) Forb All, esp. seeds & seedlings Moderate – Severe Glycosides Loss of appetite, vomiting, weakness, ataxia, spasms, in severe cases death.
Crocus, Autumn (Colchicum autumnal) Forb All, esp. bulb and seeds Moderate – Severe Alkaloids (colchiceine) Burning pain in the mouth & throat, nausea, vomiting, diarrhea, lethargy, low blood pressure, shock, convulsions, coma, death (with larger doses).
Cucumber, Wild (Marah oreganus) Vine Fruit Mild – Severe Saponic glycosides Chest pains, shortness of breath, can cause death.
Daffodil & Narcissus (Narcissus spp.) Forb All, esp. bulbs Moderate – Severe Alkaloids (glycoside) Dizziness, abdominal pain, nausea, vomiting, diarrhea. Large doses can cause trembling, convulsions & death.
Domestic plums, cherries, peaches, apricots, apples, pears, (Prunus spp., Malus spp., Pyrus spp.) Seeds, leaves, bark Mild- Moderate Cyanogenic glycoside (produces cyanide) Initial rapid breathing followed by slow, difficult breathing, anxiety, excitement, confusion, headache, vomiting, dizziness, can cause death in large quantities. Toxicity may be variable. Other related species which may be poisonous include mountain ash (Sorbus spp.), Hawthornes (Crataegus spp.), Pyracantha, Cotoneaster
Elderberry (Sambucus spp.) Shrub Leaves, stems, bark and roots Mild – Moderate Alkaloid & cyanogenic glycoside (produced cyanide) Nausea, vomiting, diarrhea. Raw fruits can cause nausea.
European bittersweet (Solanum dulcamara) Vine All, especially green berries Moderate – Severe Alkaloidal glycoside (Solanine) Abdominal pain, headache, flushed skin, tiredness. Severe cases include vomiting, thirst, difficult breathing, paralysis, dilated pupils, diarrhea, can cause death. Green potatoes contain the same chemical but in lower concentrations.
Fiddleneck or Tarweed (Amsinckia sp.) Forb All Moderate Thiaminase, Pyrrolizidine alkaloids Yes Appetite loss, timid, stupified, incoordination, liver lesions, enlarged liver (same as Tansy Ragwort) Foxglove
(Digitalis purpurea) Forb All Severe Digitoxin and other glycosides Contracted pupils, nausea, vomiting, cramps, severe headache, irregular heartbeat, labored breathing, convulsions, death, usu. a problem only in hay
Golden Chain (Laburnum anagyroides) Tree All, esp. bark & seeds Moderate – Severe Alkaloid (systine) – similar effects to nicotine Nausea, vomiting, abdominal pain, diarrhea, drowsiness, headache, dizziness, fever, irregular heartbeat, dilated pupils. Severe cases can have convulsions, coma & death. The toxicity varies widely.
Groundsel, Common (Senecio vulgaris) Forb All Moderate Pyrrolizidine alkaloids Yes Liver lesions, enlarged liver, abdominal pain, weakness, staggering, death. Liver damage is permanent. Usually only eaten in hay or when wilted. Drying or storage doesn’t destroy toxins.
Hellebore, False
(Veratrum spp.)
Forb All, esp. the rhizome Moderate – Severe lkaloids Abdominal pain, vomiting diarrhea, paralysis, spasms. In severe cases can cause death. Can cause birth defects if eaten during certain gestation periods.
Hemlock, Poison (Conium maculatum) Forb All Severe Coniine and other alkaloids Teeth grinding, muscle spasms, respiratory failure, death.
Hemlock, Water (Cicuta spp.) Forb All Severe Cicutoxin Nausea, salivation, vomiting, convulsions, fever, low hear rate, abdominal pain, dilated pupils, delirium, coma, respiratory paralysis, death. Water Parsley (Oenanthe spp.) may contain similar toxin.
Holly, English (Ilex aquifolium) Shrub Berries, leaves Mild Glycosides and alkaloids Nausea, vomiting, diarrhea, drowsiness.
Horse Chestnut (Aesculus hippocastanum) Tree All Moderate - Severe Saponin glycoside, alkaloids Inflammation of mucous membranes, vomiting, thirst, weakness, muscular twitching, dilated pupils, stupor, paralysis. Coma & death can occur in severe cases.
Horsetail (Eqisetum arvense) Fern-ally All Mild - Moderate Thiaminase Yes Destroys vitamin B1 – Symptoms include weight loss, weakness, eventual death.
Iris or Yellow Flag
(Iris pseudacorus)
Forb All, esp. rhizomes Moderate – Severe Glycoside Abdominal pain, nausea, vomiting, diarrhea, fever, large doses can cause death.
Ivy, English
(Hedera helix)
Vine All, esp. leaves & berries Moderate Triterpene saponins (glycosides) Large quantities cause vomiting, diarrhea, spasms, staggering, paralysis.
Knapweed, Russian and Yellowstar Thistle
(Centaurea spp.)
Forb All Moderate Yes Brain deterioration resulting in “Chewing disease”, can eventually cause death by starvation.
Knotweeds
(Polygonum spp.)
Forb All Mild Oxalic acid Large quantities can cause interference with calcium metabolism in the body & possible phototoxicity.
Lambsquarters
(Chenopodium album)
Forb All Mild Oxalates Large quantities can cause interference with calcium metabolism in the body & possible phototoxicity.
Larkspur
(Delphinium spp.)
Forb All Severe Alkaloids (delphinine) Constipation, bloat, dilation of pupils, vomiting, depression, paralysis, death.
Laurel, English (Prunus laurocerasus) Shrub Seeds, leaves, bark Mild - Moderate Cyanogenic glycoside (produces cyanide) Initial rapid breathing followed by slow, difficult breathing, anxiety, excitement, confusion, headache, vomiting, dizziness, can cause death in large quantities. Toxicity may be variable. Other related species which may be poisonous include mountain ash (Sorbus spp.), Hawthornes (Crataegus spp.), Pyracantha, Cotoneaster.
Lily of the Valley (Convallaria majalis) Forb All Severe Cardiac glycosides (digitalis-like) Burning pain in mouth & throat, salivation, nausea, vomiting, abdominal pain, headache, dilated pupils, slow & irregular heartbeat, sometimes coma and death.
Locust, Black or Honey (Robinia pseudo-acacia) Tree All Mild - Moderate Poisonous proteins Lassitude, nausea, vomiting, abdominal pain, diarrhea, delirium, coma, death in livestock in severe cases.
Lupine (Lupinus spp.) Forb All Moderate Alkaloids (lupinine) Yes Birth defects, spasms, vomiting, nausea, dizziness, headache, abdominal pain, & in severe cases death.
Nightshade, Black (Solanum nigrum)
Nightshade, Hairy (Solanum sarrachoides)
Vine All, especially green berries Moderate – Severe Alkaloidal glycoside (Solanine) Abdominal pain, headache, flushed skin, tiredness. Severe cases include vomiting, thirst, difficult breathing, paralysis, dilated pupils, diarrhea, can cause death. Green potatoes contain the same chemical but in lower concentrations.
Oak (Quercus spp.) Tree All, but esp. acorns Slight Tannins (?) Constipation, blood in urine.
Pea, Wild; Sweet Pea (Lathyrus spp.) Forb Foliage, seeds Mild Toxic amino acids Paralysis, convulsions, death. Toxic only in large quantities.
Pigweed (Amaranthus spp.) Forb All Mild Oxalates, nitrates Large doses can cause fluid accumulation around kidneys.
Poison Oak, Poison Ivy (Toxicodendron spp.) Shrub/ Vine All Mild - Moderate Oleoresin (urushiol) Yes Itching, burning, redness of skin, blisters
Ponderosa Pine (Pinus ponderosa) Tree Needles Mild - Moderate Abortion
Ragwort, Tansy (Senecio jacobea) Forb All Moderate Pyrrolizidine alkaloids Yes Liver lesions, enlarged liver, digestive disturbances, restlessness, lack of coordination, weakness, staggering, death. Liver damage is permanent. Usually only eaten in hay or when wilted. Drying or storage doesn’t destroy toxins. Toxins can contaminate milk & honey.
Rhododendron (Rhododendron spp.) Shrub All Mild – Severe Glycosides Burning of lips, mouth, salivation, nausea, severe vomiting, coma & death in the most severe cases. The toxin can contaminate honey.
Rhubarb (Rheum rhabarbarum) Forb Leaves Moderate Oxalic acid & oxalates (irritant poison) Abdominal pain, nausea, vomiting, difficulty breathing, drowsiness, large doses can cause convulsions, coma & death. Oxalic acid interferes with calcium metabolism as well.
Scotch Broom (Cytisus scoparius) Shrub All Mild - Moderate Quinolizidine alkaloids Nausea, vomiting, dizziness, headache, abdominal pain.
Serviceberry (Amalanchier alnifolia) Shrub Leaves, twigs Mild - Moderate Cyanogenic glycoside (produces cyanide) Initial rapid breathing followed by slow, difficult breathing, anxiety, excitement, confusion, headache, vomiting, dizziness.
Skunk Cabbage (Lysichitum americanum) Forb All Mild – Moderate Calcium oxalate crystals Physical irritation and swelling of mouth, throat, etc. as crystals pierce the skin.
Snowberry (Symphoricarpos albus) Shrub Berries Moderate - Severe Alkaloids Severe Vomiting, dizziness, semi-comatose state.
Sorrel (Rumex spp.) Forb All Mild Oxalic acid Large quantities can cause interference with calcium metabolism in the body.
St. John’s-Wort or Goatweed, Klamath Weed (Hypericum perforatum) Forb All Mild - Moderate Hypericin Photosensitization – blisters, swelling and lesions on the skin, particularly light-skinned animals. Subsequent exposure has more severe symptoms. Loss of appetite, diarrhea, increased respiration & heartbeat, high temp., blindness, convulsions, sometimes coma & death. Symptoms are often delayed.
Swamp laurel (Kalmia sp.) Shrub Leaves, flowers Mild – Moderate Andromedo-toxin, arbutin Burning of lips, mouth, salivation, nausea, severe vomiting, coma & death in the most severe cases.
Tansy, Common (Tanacetum vulgare) Forb All Moderate - Severe Tanacetin Rapid pulse, stomach inflammation, convulsions, abortion, occasionally fatal. However, rarely grazed because of strong taste and smell.
Tarweed (Amsinckia spp.) Forb All Moderate Pyrrolizidine alkaloids Yes Liver lesions, enlarged liver, digestive disturbances, restlessness, lack of coordination, weakness, staggering, death. Liver damage is permanent. Usually only eaten in hay or when wilted. Drying or storage doesn’t destroy toxins.
Vetch, Common (Vicia sativa) Forb Foliage, seeds Mild - Severe Cyanogenic glycosides (produces cyanide) Amount of toxins in plants highly variable. Initial rapid breathing followed by slow, difficult breathing, anxiety, excitement, confusion, headache, vomiting, dizziness, can cause death.
Yarrow (Achillea millefolium) Forb All Mild Glucosides & alkaloid If eaten in quantity can cause gastric problems.
Yew (Taxus brevifolia) Tree All, except perhaps the flesh around the seed. Moderate – Severe Alkaloid (taxine), ephedrine, cyanogenic glycoside Gastroenteritis, nausea, vomiting, diarrheas, rash, drowsiness, irregular heartbeat, labored breathing, trembling, collapse. Large amounts can cause death.

* Most poisonous plants are not readily consumed because they taste bad or feel bad in the mouth. Most species included in this list are not commonly grazed but may be consumed in hay, as shrub trimmings which are left accessible, as bulbs exposed through soil-turning activities, or if there is little other feed in the pasture or confinement area.

** Many of these plants have similar effects on humans! The major symptoms and effects are listed, but the list is NOT all-inclusive. Consult the local Poison Control Center for a complete listing and information about treatment.

SOURCES:
Plants that Poison Livestock in Thurston County, by Thurston County Noxious Weed Control Agency
Pasture Management for Horses and Ponies, by Gillian McCarthy
Common Poisonous Plants and Mushrooms of North America, by Nancy J. Turner and Adam F. Szczawinski
A Guide to Selected Weeds of Oregon (Supplement), by Hawkes, et.al., Oregon Department of Agriculture 1989

Compiled by: Marty Chaney, Pasture Management Specialist
USDA – Natural Resources Conservation Service, Olympia, WA 12/99

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Pierce Conservation District
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Puyallup, WA 98371
Phone: (253) 845-9770

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