22 Common Poisonous Plants—and What to Do After Exposure

There is no official list of exactly 22 “common poisonous plants.” The plants below are 22 poisonous or harmful species and plant groups people may encounter in U.S. homes, gardens, construction and landscaping sites, roadsides, wetlands, trails, and recreational areas. They are not equally dangerous: some mainly cause an itchy rash or a mouth injury, while others can cause seizures, heart-rhythm problems, respiratory failure, or multi-organ damage.

If someone may have swallowed plant material, call Poison Control at 1-800-222-1222 in the United States. Call 911 for a seizure, collapse, trouble breathing, severe facial or throat swelling, or an unconscious person. Do not induce vomiting.

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What “poisonous plant” means

“Poisonous” is a broad practical term, not a severity ranking. A plant can harm someone through several different mechanisms:

• Allergic contact dermatitis: Poison ivy, poison oak, and poison sumac contain urushiol, an oily allergen that can cause a delayed, intensely itchy rash.
• Phototoxic injury: Giant hogweed and wild parsnip contain compounds that can cause burn-like inflammation when sap-covered skin is exposed to ultraviolet light.
• Irritant or mechanical injury: Dieffenbachia, peace lily, and philodendron contain needle-like calcium oxalate crystals. Holly leaves can also puncture the mouth.
• Gastrointestinal poisoning: Pokeweed, holly, daffodil, and azalea commonly cause mouth or stomach irritation, vomiting, diarrhea, or abdominal pain.
• Cardiac toxicity: Oleander, foxglove, lily-of-the-valley, and yew can interfere with the heart’s electrical activity or pumping.
• Neurologic toxicity: Poison hemlock, water hemlock, and jimsonweed can cause weakness, delirium, seizures, paralysis, or breathing failure.
• Cellular toxins: Chewed or damaged castor beans and rosary peas can release ricin or abrin, toxins that injure cells throughout the body.
• Multi-system toxicity: Autumn crocus can cause severe gastrointestinal illness followed by bone-marrow, muscle, respiratory, and multi-organ complications.

Severity depends on the species, the plant part, dose, preparation, route of exposure, age, health, and how quickly treatment begins. Poison Control notes that plant exposures range from mild irritation to severe illness and death; “natural” does not mean safe. See its illustrated plant guide for additional examples.

Quick reference: 22 plants to recognize

The word “common” is regional. A plant may be ordinary in one state or habitat and uncommon in another. Scientific names matter because one common name can refer to several species with different risks.

Plant	Where encountered	Dangerous part or route	Main hazard	Typical response
Poison ivy	Woodlands, yards, fences, trails	Urushiol on plant, objects, animals, and smoke	Delayed allergic rash	Wash promptly; call for severe rash or breathing symptoms
Poison oak	Western and eastern U.S. woodlands, brush, yards	Urushiol; smoke	Allergic dermatitis	Wash promptly; avoid burning
Poison sumac	Wetland and swamp habitats, especially eastern regions	Urushiol; smoke	Allergic dermatitis	Wash promptly; avoid burning
Giant hogweed	Some roadsides, stream edges, and disturbed areas	Sap plus ultraviolet light	Severe phototoxic burns	Rinse, cover from sunlight, and report it
Wild parsnip	Roadsides, fields, ditches, trails	Sap plus ultraviolet light	Blistering photodermatitis	Rinse and protect from sunlight
Poison hemlock	Fields, roadsides, ditches, disturbed ground	All parts, especially if swallowed	Neurotoxicity and paralysis	Call Poison Control immediately
Water hemlock	Wet meadows, ditches, stream banks	Especially tuberous roots	Violent seizures	Emergency medical help
Oleander	Warm-climate landscaping and containers	Leaves, flowers, stems, sap, preparations	Cardiac toxicity	Call Poison Control immediately
Foxglove	Ornamental gardens and naturalized areas	All parts	Cardiac glycoside poisoning	Immediate medical guidance
Lily-of-the-valley	Gardens, bouquets, woodland plantings	Berries, leaves, flowers, vase water	Cardiac glycosides	Call Poison Control; do not wait for symptoms
Azalea/rhododendron	Landscapes and gardens	Leaves, flowers, nectar, contaminated honey	GI and cardiovascular toxicity	Call Poison Control after ingestion
Yew	Hedges, landscaping, cemeteries	Needles and seeds	Cardiac and neurologic toxicity	Urgent Poison Control guidance
Castor bean	Ornamental plantings and warm climates	Chewed or crushed seeds	Ricin toxicity	Immediate Poison Control guidance
Rosary pea	Ornamental vines, imported jewelry, craft items	Chewed, cracked, drilled, or broken seeds	Abrin toxicity	Emergency-risk ingestion
Jimsonweed	Disturbed soil, fields, roadsides	Seeds, leaves, homemade preparations	Anticholinergic delirium	Emergency help for symptoms
Pokeweed	Fields, woodland edges, gardens	Whole plant, especially roots and berries	GI toxicity	Call Poison Control after ingestion
Holly	Landscaping and seasonal decorations	Berries, leaves, roots	GI irritation and sharp leaves	Call for persistent or severe symptoms
Daffodil	Gardens, bouquets, naturalized plantings	Bulbs, leaves, flowers	Lycorine and oxalates	Call Poison Control after bulb ingestion
Autumn crocus	Ornamental gardens and some naturalized areas	Any plant part	Colchicine poisoning	Immediate emergency guidance
Dieffenbachia	Indoor and tropical ornamental plantings	Leaves and stems if chewed	Calcium oxalate crystals	Rinse mouth; emergency care for airway swelling
Peace lily	Common indoor houseplant	Leaves, flowers, stems if chewed	Calcium oxalate crystals	Rinse mouth; call Poison Control
Philodendron	Common indoor and outdoor ornamental plant	Leaves, stems, cuttings if chewed	Calcium oxalate crystals	Rinse mouth; urgent care for breathing trouble

Contact hazards: plants that can injure skin or eyes

1. Poison ivy (Toxicodendron radicans)

Where found: Poison ivy grows in many parts of the United States in woods, yards, fencerows, and along trails. It may grow as a low plant, shrub, or climbing vine.

What is dangerous: Urushiol is the oily allergen in the leaves, stems, roots, and vines. Contact can occur directly, or through tools, work clothes, boots, pets, and other objects that carry the oil. Dead plants may retain urushiol. Smoke from burning poison ivy can carry the oil into the lungs.

Recognition: The three-leaflet pattern is a useful warning sign, but it is not a complete identification system. Leaf shape and color vary, and many harmless plants also have three leaflets. Do not touch an uncertain plant to test it.

Symptoms and response: The rash is usually delayed and may appear as itching, redness, swelling, streaks, bumps, and blisters. New areas can appear at different times because exposure and absorption are uneven. The rash is not spread by blister fluid; contaminated oil is the concern. Wash exposed skin promptly with water and soap or a degreasing cleanser, then wash clothing and tools. Seek medical care for extensive blistering, facial or genital involvement, eye exposure, breathing symptoms, or rapidly worsening swelling. Read the Poison Control guidance on poison ivy, oak, and sumac.

2. Poison oak (Toxicodendron diversilobum and Toxicodendron pubescens)

Where found: Western poison oak and eastern poison oak occur in different parts of the country, in brush, woodlands, yards, and disturbed areas.

What is dangerous: Like poison ivy, poison oak contains urushiol. Damaged foliage, stems, vines, clothing, equipment, and smoke can all be exposure routes.

Recognition and symptoms: Leaflets may occur in groups of three to five, and the appearance differs between western and eastern species. A delayed, itchy, blistering allergic rash is typical. Because lookalikes are common, do not rely only on “leaves of three.” Wash promptly after suspected contact and never burn the plant. The CDC/NIOSH poisonous-plant guidance explains the differences between allergic, irritant, and phototoxic dermatitis.

3. Poison sumac (Toxicodendron vernix)

Where found: Poison sumac is most associated with wet, swampy habitats and is not equally common throughout the United States.

What is dangerous: Its urushiol can cause allergic dermatitis through contact with plant oil or smoke from burning plant material. The oil can remain on clothing, tools, and other surfaces.

Recognition and response: Poison sumac commonly has 7–13 leaflets arranged along a stem, unlike the three-leaflet shortcut associated with poison ivy. Because identification can be difficult, keep away from suspected plants and do not burn them. Rinse exposed skin for at least 15 minutes and launder contaminated items. Severe rash, eye exposure, facial swelling, or breathing trouble warrants medical attention.

4. Giant hogweed (Heracleum mantegazzianum)

Where found: This invasive plant is reported in parts of the United States, particularly in some northeastern and northwestern areas, along roadsides, stream corridors, and other disturbed sites. It is not common nationwide.

What is dangerous: Its sap contains furanocoumarins. When sap-covered skin is exposed to ultraviolet light, the reaction can produce painful burn-like inflammation and blisters, often within 24–48 hours. Later pigmentation, scarring, and prolonged sun sensitivity can occur. Sap in the eyes can threaten vision.

Recognition: Suspected giant hogweed may be very large, with broad divided leaves, a thick stem that can have purple markings, and large white flower clusters. Size alone is not enough: several nonidentical plants are lookalikes.

What to do: Rinse sap from skin immediately with plenty of water, cover the area, and keep it out of sunlight. New York guidance recommends protecting the area from sunlight for 48 hours; follow medical advice for burns or eye exposure. Do not touch it bare-handed, mow it, or use a weed-whacker. Keep workers and the public away and contact the appropriate state or local invasive-species authority. See New York State’s giant hogweed guidance.

5. Wild parsnip (Pastinaca sativa)

Where found: Wild parsnip commonly appears along roadsides, trails, fields, ditches, and other sunny disturbed areas.

What is dangerous: Sap containing furanocoumarins can cause phytophotodermatitis when it reaches skin that is then exposed to ultraviolet light. The result may be painful redness, blisters, and later dark discoloration.

Recognition and response: Wild parsnip can be confused with edible parsnip, wild carrot, and other members of the carrot family. Do not forage or handle it based on a photograph or a single visual feature. After contact, rinse the skin, remove contaminated clothing, and protect the area from sunlight. Seek care for extensive blistering, eye exposure, or severe pain. CDC/NIOSH identifies wild parsnip and giant hogweed as plants whose sap can react with UV light.

Wild, garden, and foraging hazards

6. Poison hemlock (Conium maculatum)

Where found: Poison hemlock grows in fields, roadsides, ditches, stream edges, and disturbed soil. It is often encountered where people are clearing or maintaining overgrown property.

What is dangerous: Coniine and related piperidine alkaloids affect the nervous system. All parts can be dangerous, including leaves, stems, fruit, and roots. The most common serious exposure is mistaken identity: the plant may be confused with parsley, wild carrot, wild parsnip, wild celery, or another edible plant.

Recognition and symptoms: A hollow stem with purple or reddish spots, lacy foliage, white flower clusters, and an unpleasant odor are clues, not guarantees. Symptoms can include nausea, dizziness, weakness, tremors, progressive muscle paralysis, and breathing difficulty. If ingestion is possible, call Poison Control immediately. Do not pull, cut, dig, burn, or forage an uncertain hemlock without appropriate training and protective procedures. Consult Poison Control’s poison-hemlock information and the USDA identification notes.

7. Water hemlock (Cicuta spp.)

Where found: Water hemlock grows in wet meadows, ditches, stream banks, and seepage areas.

What is dangerous: Cicutoxin is a powerful central-nervous-system convulsant. The tuberous roots are especially dangerous, although toxicity varies by species and plant part. Water hemlock is a different plant from poison hemlock and should not be treated as the same poisoning.

Symptoms and response: Twitching, excessive salivation, tremors, violent seizures, coma, and rapid death are possible after ingestion. Suspected ingestion is an emergency: call 911 for symptoms and contact Poison Control or emergency medical services immediately. Do not attempt home treatment or induce vomiting. The USDA Agricultural Research Service provides information on water hemlock’s toxicity.

8. Pokeweed (Phytolacca americana)

Where found: Pokeweed grows in fields, woodland margins, gardens, and disturbed ground. Its dark purple berries on red stems can look like grapes.

What is dangerous: The entire plant contains toxic compounds, with the roots especially concerning. Berries, leaves, and roots can cause poisoning.

Symptoms and response: Stomach pain, nausea, vomiting, and diarrhea are common. More serious root exposures can involve bloody vomit or stool and low blood pressure. Some traditional recipes call for repeated boiling of young leaves, but that is not general safety advice; preparation errors and plant variation can be dangerous. Do not eat unidentified pokeweed or give it to children. Call Poison Control after ingestion, particularly for a child, a root exposure, persistent vomiting, blood, weakness, or dehydration. See Poison Control’s information on pokeberries.

9. Holly (Ilex spp.)

Where found: Holly is widely planted in landscapes and is common in seasonal decorations.

What is dangerous: Berries, leaves, roots, and swallowed plant material can cause gastrointestinal irritation. The stiff, spiny leaves can puncture the mouth or throat.

Symptoms and response: Nausea, vomiting, diarrhea, abdominal pain, and dehydration may follow ingestion. Bright berries can attract children, but the risk varies with the amount swallowed; do not claim that one or two berries are automatically fatal. Remove plant pieces from the mouth, do not induce vomiting, and call Poison Control for a child exposure, an uncertain amount, or significant symptoms. Use the Poison Control guidance on holly.

10. Autumn crocus (Colchicum autumnale)

Where found: Autumn crocus is an ornamental garden plant and may be naturalized in some areas. It is not a true spring crocus, despite the similar common name.

What is dangerous: Any plant part can contain colchicine. It can cause severe gastrointestinal illness followed by dehydration, bone-marrow injury, multi-organ damage, muscle weakness, paralysis, respiratory failure, and death in serious cases.

What to do: Any suspected ingestion needs immediate Poison Control or emergency medical guidance. Do not wait for symptoms and do not assume that an attractive ornamental plant is safe. See the CDC/NIOSH emergency response information for colchicine.

Ornamental plants with systemic toxicity

11. Oleander (Nerium oleander)

Where found: Oleander is common in warm-climate landscaping and is also grown in containers.

What is dangerous: Leaves, flowers, stems, sap, and plant preparations contain cardiac glycosides. Swallowing the plant can cause gastrointestinal illness, weakness, abnormal heart rhythms, cardiovascular collapse, and death.

What to do: Never make tea or a medicinal preparation from oleander. Remove plant material from the mouth, do not induce vomiting, and call Poison Control immediately after ingestion. Severe weakness, fainting, palpitations, or breathing trouble requires 911. The Poison Control plant guide and ASPCA’s oleander information describe its cardiac-glycoside hazard.

12. Foxglove (Digitalis purpurea)

Where found: Foxglove is grown as an ornamental and can naturalize in some areas.

What is dangerous: All parts—including flowers, leaves, berries, and seeds—contain digitalis-like cardiac glycosides. It is sometimes mistaken for an edible plant or used incorrectly in homemade tea or herbal preparations.

Symptoms and response: Nausea, vomiting, weakness, dizziness, a slow or irregular heartbeat, and potentially life-threatening cardiac effects can occur. Digitalis is used as a controlled medicine in precise pharmaceutical preparations; raw foxglove is not a safe substitute. Call Poison Control immediately after a possible ingestion and do not induce vomiting. Read Poison Control’s foxglove guidance.

13. Lily-of-the-valley (Convallaria majalis)

Where found: This fragrant plant occurs in gardens, woodland plantings, bouquets, and floral arrangements.

What is dangerous: Berries, leaves, flowers, and other plant material contain cardiac glycosides. Water from a vase containing lily-of-the-valley should also be treated as a possible exposure if someone drinks it.

Symptoms and response: Vomiting may occur, along with a slow or abnormal heart rate. Children may mistake the berries for edible fruit. Call Poison Control rather than waiting for symptoms, and preserve the plant or a photograph if it can be done safely. See Poison Control’s berry guidance.

14. Azalea and rhododendron (Rhododendron spp.)

Where found: These shrubs are common in residential landscapes and gardens.

What is dangerous: Grayanotoxins occur in plant material, including leaves and flowers, and can also contaminate honey made from nectar gathered in dense rhododendron populations. This “mad honey” exposure is a geographic and food-related edge case, not the usual result of touching an azalea.

Symptoms and response: A small accidental ingestion may cause mouth irritation, nausea, and vomiting. Larger exposures can cause low blood pressure, a slow heart rate, confusion, or abnormal heart rhythm. Severity varies substantially; do not describe every azalea exposure as fatal. Call Poison Control after ingestion, especially for a child or anyone with weakness, dizziness, fainting, or heart symptoms. See Poison Control’s azalea and rhododendron information.

15. Yew (Taxus spp.)

Where found: Yew is used in hedges, foundation plantings, landscaping, and cemeteries.

What is dangerous: Taxine compounds are found in the needles and in the seed inside the red fleshy aril. The red covering does not make the seed safe, and homemade tea made from needles is particularly hazardous. The fleshy portion is treated differently from the seed, but the safest rule is not to eat any part of a yew plant.

Symptoms and response: Yew can cause cardiac and neurologic toxicity, including weakness, dizziness, abnormal heart rhythms, collapse, and death. Call Poison Control immediately after any ingestion. Pacific yew was the original source of the purified medicine paclitaxel; that fact does not make raw yew safe. See Poison Control’s yew guidance.

16. Castor bean (Ricinus communis)

Where found: Castor bean is grown as an ornamental in some gardens and is more common outdoors in warm climates.

What is dangerous: The seed contains ricin. Toxicity rises when the hard seed is chewed or crushed, releasing the toxin. Do not repeat claims that one seed always kills: risk varies with the seed, amount, person, and whether it was chewed.

Symptoms and response: Nausea, vomiting, diarrhea, abdominal pain, dehydration, bleeding, and possible multi-organ injury can occur. Any swallowed castor bean merits immediate Poison Control guidance. Refined castor oil is different from raw castor beans: ordinary processing removes ricin from the oil. See Poison Control’s castor-bean explanation.

17. Rosary pea (Abrus precatorius)

Where found: Rosary pea is an ornamental vine in some warm regions. Its glossy red seeds with a black spot may also appear in imported jewelry, toys, or craft items.

What is dangerous: The seeds contain abrin, a protein toxin that disrupts cellular protein production. Risk rises sharply when a seed is chewed, cracked, drilled, or otherwise broken. An intact seed may release less toxin, but any ingestion is potentially dangerous.

Symptoms and response: Delayed vomiting, diarrhea, abdominal pain, bloody stool, seizures, organ failure, and death are possible. Do not handle broken seeds unnecessarily. Call Poison Control immediately after a swallowed or chewed seed and call 911 for severe symptoms. See Poison Control’s rosary-pea information.

18. Jimsonweed (Datura stramonium)

Where found: Jimsonweed grows in disturbed soil, fields, roadsides, vacant lots, and other warm, sunny locations.

What is dangerous: Seeds and leaves contain atropine, scopolamine, and related tropane alkaloids. Homemade teas, food preparations, and intentional misuse have caused serious poisonings.

Symptoms and response: Anticholinergic poisoning can cause dry mouth, dilated pupils, blurred vision, flushed or hot skin, a fast heartbeat, urinary retention, agitation, confusion, hallucinations, seizures, coma, and occasionally death. Severe confusion, overheating, a very fast heartbeat, or altered consciousness requires emergency help. Call Poison Control immediately and do not attempt to treat it as a recreational or herbal preparation. See California Poison Control’s anticholinergic-plant guidance and the CDC report on jimsonweed poisoning.

19. Daffodil (Narcissus spp.)

Where found: Daffodils are common in gardens, bouquets, and naturalized plantings.

What is dangerous: The bulb contains the highest concentration of toxic compounds, including lycorine and oxalates. Bulbs can be mistaken for onions or other edible bulbs. Leaves and flowers can also cause problems if swallowed.

Symptoms and response: Burning in the mouth, nausea, vomiting, abdominal pain, and diarrhea are typical. Persistent vomiting, severe throat pain, drooling, or difficulty swallowing requires medical evaluation. Call Poison Control after a bulb ingestion, particularly when the amount or plant is uncertain. See Poison Control’s daffodil information.

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Common houseplants that injure the mouth

Dieffenbachia, peace lily, and philodendron contain insoluble calcium oxalate crystals, also called raphides. When a leaf or stem is chewed, the crystals cause immediate mechanical irritation rather than the delayed whole-body poisoning associated with some seeds or cardiac plants. Most small exploratory exposures cause localized pain and swelling, but airway swelling is an emergency.

20. Dumbcane or dieffenbachia (Dieffenbachia spp.)

Dangerous part and mechanism: Leaves and stems release calcium oxalate crystals when chewed or crushed.

Symptoms: Immediate burning pain in the mouth, drooling, irritation and swelling of the lips, tongue, and throat, nausea, and vomiting may occur. Swelling near the airway can make breathing difficult.

What to do: Remove plant pieces from the mouth and rinse or wipe the mouth. Do not induce vomiting. Contact Poison Control for case-specific advice; call 911 for trouble breathing, severe throat swelling, or inability to swallow. Veterinary references also list dieffenbachia as toxic to animals; human and animal advice should be kept separate. See the Merck Veterinary Manual overview of toxic houseplants.

21. Peace lily (Spathiphyllum spp.)

Dangerous part and mechanism: Leaves, flowers, and stems contain insoluble calcium oxalate crystals.

Symptoms and response: Chewing can cause immediate mouth and throat pain, drooling, lip or tongue swelling, coughing, nausea, and vomiting. Most exploratory exposures cause localized irritation, but breathing difficulty or severe swelling requires 911. Remove plant material, rinse the mouth, and call Poison Control. A peace lily is not a true lily: it is an oxalate irritant, while true lilies are a separate and particularly serious kidney hazard for cats. See Poison Control’s peace-lily article and its true-lily guidance.

22. Philodendron (Philodendron spp.)

Dangerous part and mechanism: Leaves, stems, and cuttings contain insoluble calcium oxalate crystals that irritate tissue when chewed.

Symptoms and response: Immediate oral pain, drooling, mouth swelling, coughing, nausea, and throat irritation are possible. Remove plant material, rinse the mouth, and contact Poison Control. Call 911 for breathing trouble, severe swelling, or an unresponsive person. Philodendron is also listed in veterinary toxic-plant references, but animal severity should not be substituted for human medical advice.

Symptoms that should not be ignored

Plant exposures can affect different body systems. Call Poison Control promptly for a suspected ingestion even when symptoms have not started. Seek emergency help for:

• Skin or eyes: severe pain, extensive blistering, facial or genital swelling, eye pain, vision changes, or breathing symptoms after sap or smoke exposure.
• Digestive system: repeated vomiting, severe abdominal pain, bloody vomit or stool, inability to swallow, heavy drooling, or signs of dehydration.
• Heart: fainting, palpitations, a slow or irregular heartbeat, severe weakness, dizziness, or collapse.
• Nervous system: confusion, agitation, hallucinations, muscle weakness, tremors, seizures, loss of consciousness, or difficulty breathing.
• Airway: tongue or throat swelling, choking, wheezing, or any trouble breathing.

Safe removal and disposal around construction sites and properties

Before clearing volunteer vegetation, stop work if a plant is unidentified and could be a contact or ingestion hazard. Keep children, pets, livestock, and unprotected workers away. A photograph can help an expert make a provisional identification, but an app or online image match is not proof that a plant is safe to touch or eat.

Poison ivy, oak, and sumac

• Wear protective clothing and gloves. Avoid touching your face.
• Wash exposed skin promptly and clean tools, boots, clothing, and equipment.
• Wash contaminated clothing separately.
• Do not burn cuttings, brush, or dead vines. Urushiol can remain active after the plant dies, and smoke can cause severe respiratory exposure.

Giant hogweed and wild parsnip

• Do not touch suspected giant hogweed bare-handed.
• Do not mow or use a weed-whacker on suspected phototoxic plants, which can spray sap.
• Keep sap away from skin and eyes; use suitable protective clothing and eye protection under an appropriate site-safety plan.
• Rinse any exposure immediately and keep it out of sunlight.
• Report suspected giant hogweed to the relevant state or local invasive-species, agricultural, or environmental authority instead of encouraging untrained removal.

Poison hemlock and water hemlock

• Do not pull, dig, cut, or burn uncertain hemlock without species-specific training, protective equipment, and a planned disposal method.
• Do not use a single clue—such as purple spots, an odor, or a photograph—to decide that a plant is edible.
• Keep the area closed to children, pets, and livestock until the hazard is identified and controlled.

Do not apply a universal herbicide recipe. Product labels, invasive-plant rules, disposal requirements, and permitted control methods vary by state and municipality. A qualified local contractor, extension service, or public agency can provide site-specific advice.

Poisonous plants and pets

Myths and identification mistakes

“Leaves of three, let it be” identifies every poisonous plant.

No. It is mainly a warning associated with poison ivy. Poison oak may have three to five leaflets, while poison sumac commonly has 7–13. Many harmless plants also have three leaflets.

Poison ivy spreads when someone scratches the blisters.

No. Blister fluid does not spread the rash. New lesions can appear at different times because different areas absorbed different amounts of urushiol. Contaminated oil on skin, clothing, tools, pets, or other objects can cause additional exposure. Burning the plant can expose the lungs.

Any amount of any poisonous plant is fatal.

No. Some small exposures cause no symptoms or only local irritation, while other plants require urgent evaluation after a small or uncertain ingestion. Risk depends on the plant, part, dose, preparation, route, and person. Avoid generalized claims such as “one leaf” or “three berries always kills.”

Castor oil contains the same ricin as castor beans.

Refined castor oil is not the same as a raw or chewed castor bean. Ordinary processing removes ricin from the oil. The raw seed remains a poisoning concern, particularly when chewed or crushed.

Peace lilies are the same as true lilies.

No. Peace lilies (Spathiphyllum) contain insoluble calcium oxalates that irritate the mouth. True lilies belong to a different group and can cause life-threatening kidney injury in cats.

Poison hemlock and water hemlock are the same.

No. They are different plants with different toxins and clinical patterns. Water hemlock is especially associated with violent seizures and highly toxic roots; poison hemlock can cause weakness, paralysis, and respiratory failure.

Cooking makes every wild plant safe.

No. Preparation can fail to remove toxins, and the correct method may depend on the exact species and plant part. Do not turn traditional food practices into general safety advice. Poison Control specifically cautions that there is no evidence supporting the safety of eating milkweed after cooking or boiling. Unidentified wild plants should not be eaten.

Poinsettia is a deadly houseplant.

This is a common myth. Poinsettia may cause irritation, but it should not be presented as a deadly plant. It is also not a substitute for accurate information about genuinely dangerous ornamental plants.

How to identify a plant safely

1. Do not taste, chew, or handle an uncertain plant to test it.
2. Take clear photographs from a safe distance, including the whole plant, leaves, stem, flowers, fruit, and habitat.
3. Record the location, season, and whether it was a houseplant, landscape plant, roadside weed, or wetland plant.
4. Use the scientific name and a reliable regional source, extension service, botanist, or poison center. Common names can refer to unrelated plants.
5. If exposure has already occurred, call Poison Control first. Identification is useful, but treatment should not wait for a perfect photograph.

The article’s 22 plants were selected because they are realistically encountered in at least one U.S. setting: homes, gardens, landscaping, roadsides, fields, wetlands, trails, seasonal decorations, bouquets, imported jewelry, or craft materials. They are not a national “top 22” ranking. Poison-center annual reports cover all poison categories and should not be read as a ranking of plant danger; see the current National Poison Data System report index and the latest report announcement for surveillance context.

Frequently Asked Questions

What is the most dangerous common poisonous plant?

There is no universally valid winner because toxicity depends on the species, plant part, dose, route, and speed of treatment. Water hemlock is an exceptionally high-risk North American plant, particularly because its roots can cause violent seizures, but oleander, yew, autumn crocus, rosary pea, castor bean, and several other plants can also cause life-threatening poisoning. Treat every suspected ingestion as a Poison Control question rather than relying on a ranking.

Can touching a poisonous plant kill you?

Ordinary contact with poison ivy, oak, or sumac usually causes allergic dermatitis rather than systemic poisoning. Giant hogweed and wild parsnip sap can cause severe phototoxic burns, especially after sunlight exposure. Touching is not the main danger for many plants on this list, but sap in the eyes, severe airway swelling after chewing an oxalate plant, or smoke inhalation from burning urushiol-containing plants can be emergencies.

What should I do if a child eats an unknown berry?

Remove remaining material from the mouth, do not induce vomiting, and call Poison Control at 1-800-222-1222 in the United States. Keep the plant or take a photograph if it can be done safely. Call 911 for seizure, collapse, trouble breathing, severe swelling, or inability to awaken. Do not wait for symptoms, since some plant toxins have delayed effects.

Can I identify a poisonous plant from a photograph?

A photograph may support a provisional identification, but it is not definitive. Common names, regional variation, seasonal appearance, and lookalikes make plant identification difficult. Photograph the whole plant, leaves, stem, flowers or berries, and habitat without touching it, then confirm with a reliable regional expert or Poison Control. Never use an image match alone to decide that a wild plant is edible.

Should I remove poison hemlock from my property?

Do not pull, cut, dig, mow, or burn an uncertain hemlock without species-specific training, protective equipment, and a disposal plan. Keep children, pets, and livestock away, and contact a local extension service, land-management agency, or qualified vegetation-control professional. Water hemlock and poison hemlock are different plants, so correct identification matters.

Are all parts of a poisonous plant dangerous?

Not always. Some plants are most hazardous in a particular part: water hemlock roots, daffodil bulbs, castor bean and rosary pea seeds, yew needles and seeds, and berries from several plants. Other plants, including foxglove and oleander, can be dangerous throughout the plant. Never generalize from one part to another, and ask Poison Control about the exact plant and amount.

What happens if someone drinks water from a flower vase?

Water from a vase containing lily-of-the-valley should be treated as a possible exposure because the plant contains cardiac glycosides. Remove the person from further exposure and call Poison Control for individualized advice. Do not induce vomiting or wait for symptoms.

What if there are no symptoms yet?

The absence of immediate symptoms does not prove that an ingestion is safe. Some plant toxins have delayed effects, and symptoms may begin after absorption has occurred. Call Poison Control promptly with the person’s age, health information, plant or photograph, part swallowed, estimated amount, and time of exposure.

Can I burn poison ivy after pulling it up?

No. Never burn poison ivy, poison oak, or poison sumac. Urushiol can remain on dead plants, and smoke can carry it into the lungs and cause severe respiratory reactions. Follow local disposal requirements and wash protective clothing and tools after removal.

Are poisonous plants dangerous to dogs and cats?

Some are, but animal and human risks differ. Contact a veterinarian or an animal poison service for a pet exposure; ASPCA Animal Poison Control is available at (888) 426-4435. True lilies are a particular emergency for cats because they can cause severe kidney injury. Peace lily is not a true lily and usually causes calcium-oxalate mouth irritation instead.

The Bottom Line

Do not rely on a common name, a “leaves of three” rule, or an image-search result to decide whether a plant is safe. Keep unknown plants out of mouths, stop work before clearing suspicious vegetation, never burn poison ivy or unknown brush, and call Poison Control promptly after a suspected ingestion. For a collapse, seizure, breathing difficulty, severe swelling, or unconsciousness, call 911.

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