The poisonous plants you are most likely to meet in Michigan are poison ivy, poison sumac, wild parsnip and giant hogweed, which burn or blister skin, and poison hemlock and water hemlock, which can kill if eaten. Most of the others on this list are dangerous only if they are eaten, and several are mainly a risk to pets and livestock. One plant often listed for Michigan, poison oak, does not grow in the state: the “poison oak” people report here is almost always poison ivy.
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If someone has eaten part of a plant, call Poison Control at 1-800-222-1222, which works anywhere in the US, around the clock. Call 911 for trouble breathing, seizures or unconsciousness. For pets, call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435.
- Plants That Burn or Blister Skin
- Plants That Are Poisonous to Eat
- Plants That Mainly Harm Pets and Livestock
- What to Do After Contact or Poisoning
| Plant | Botanical name | Toxic part | Main risk |
|---|---|---|---|
| Poison Ivy | Toxicodendron radicans | All parts, including bare winter stems | Itchy, blistering rash (urushiol) |
| Poison Sumac | Toxicodendron vernix | All parts | Severe rash, stronger than poison ivy |
| Giant Hogweed | Heracleum mantegazzianum | Sap | Severe burns and blisters in sunlight; can damage eyes |
| Wild Parsnip | Pastinaca sativa | Sap | Burns and blisters in sunlight |
| Stinging Nettle | Urtica dioica | Stinging hairs on leaves and stems | Burning, itchy welts for a few hours |
| Showy Lady’s Slipper | Cypripedium reginae | Glandular hairs on leaves and stems | Skin rash in sensitive people |
| Spotted Water Hemlock | Cicuta maculata | All parts, especially the roots | Violent seizures; often fatal |
| Poison Hemlock | Conium maculatum | All parts | Paralysis; can be fatal |
| Jack-in-the-Pulpit | Arisaema triphyllum | All parts, especially the root | Intense burning and swelling of the mouth and throat |
| Lily of the Valley | Convallaria majalis | All parts, including the red berries | Heart rhythm problems |
| Autumn Crocus (Meadow Saffron) | Colchicum autumnale | All parts, especially the corm | Severe vomiting and diarrhea, organ failure; can be fatal |
| Northern Blue Flag | Iris versicolor | Rhizomes (roots), less so leaves | Vomiting, diarrhea; sap irritates skin |
| Periwinkle | Vinca minor | All parts | Stomach upset; a bigger risk to pets |
| Wild Ginger | Asarum canadense | Rhizome and leaves | Kidney damage and cancer risk with repeated use |
| Wild Garlic (Meadow Garlic) | Allium canadense | Bulbs and leaves | Anemia in dogs and cats |
| Field Horsetail | Equisetum arvense | Whole plant, fresh or in hay | Nerve damage in horses (thiamine deficiency) |
| Sheep Sorrel | Rumex acetosella | Leaves | Oxalate poisoning in livestock that graze large amounts |
| Buckwheat | Fagopyrum esculentum | Whole plant | Sunlight sensitivity in livestock; allergy in some people |
Plants That Burn or Blister Skin
These plants hurt you by touch, not by being eaten. Wear long sleeves, long pants and gloves when clearing brush, and wash your skin and tools afterwards.
Poison Ivy (Toxicodendron radicans)
Poison ivy grows all over Michigan: in woods, along trails and fences, on beach dunes and in backyards. It can be a low groundcover, a shrub or a hairy vine climbing a tree. Look for leaves made of three leaflets, with the middle leaflet on a longer stalk. The leaflet edges can be smooth, toothed or lobed, and they are often glossy and reddish in spring. Northern Michigan also has western poison ivy (Toxicodendron rydbergii), a shrubby form that doesn’t climb. Both contain urushiol, an oil that causes an itchy, blistering rash in most people. It sticks to clothes, tools and pets’ fur, and it is still active on bare winter stems. Never burn poison ivy: the smoke can carry urushiol into your lungs.
Poison Sumac (Toxicodendron vernix)
Poison sumac is a shrub or small tree, usually 5 to 20 feet tall, that grows only in wet ground: bogs, fens, swamp edges and wet woods, mostly in southern Lower Michigan. Each leaf has 7 to 13 smooth-edged leaflets on a red stalk, and in fall the plant carries loose, drooping clusters of whitish berries. Harmless sumacs, like staghorn sumac, have red berries in upright clusters and grow on dry ground. Poison sumac contains even more urushiol than poison ivy, and its rash is usually worse.
Giant Hogweed (Heracleum mantegazzianum)
Giant hogweed is an invasive plant from the Caucasus that has been found at scattered sites in Michigan and is under active eradication. It is huge: 8 to 14 feet tall, with a purple-blotched, bristly stem 2 to 4 inches thick, deeply cut leaves up to 5 feet wide and white, umbrella-shaped flower heads up to 2 1/2 feet across. Its sap makes skin extremely sensitive to sunlight (phytophotodermatitis). Burns and blisters appear 1 to 2 days after contact and can leave scars for years. Sap in the eyes can cause lasting damage. Do not touch it or cut it yourself. Report it to the Michigan Department of Agriculture and Rural Development (MDARD) or through the Midwest Invasive Species Information Network (MISIN).
Wild Parsnip (Pastinaca sativa)
Wild parsnip is the escaped form of the garden parsnip, and it is now common along roadsides, trails, field edges and in unmown grass across Michigan. It grows 2 to 5 feet tall, with a grooved stem, leaves made of toothed leaflets and flat clusters of small yellow flowers in June and July. Its sap causes the same sunlight burn as giant hogweed, on a smaller scale. The typical injury is a streaky row of blisters where stems brushed bare legs or arms, often from mowing or string-trimming in shorts.
Stinging Nettle (Urtica dioica)
Stinging nettle grows in moist, rich soil along streams, woodland edges and old farmyards. It is 3 to 7 feet tall, with square stems and opposite, heart-shaped to lance-shaped leaves that have coarsely toothed edges. Both leaves and stems are covered in hollow hairs that inject histamine and other irritants when touched. The sting burns and itches for a few hours and is not dangerous. Young nettle leaves are edible once cooked or dried, because heat destroys the stinging hairs.
Showy Lady’s Slipper (Cypripedium reginae)
The showy lady’s slipper is Michigan’s largest native orchid. It is 1 to 3 feet tall, with pink-and-white pouched flowers in June. It grows in fens, bogs and wet cedar swamps. Its leaves and stems are covered in glandular hairs that can cause a rash similar to poison ivy in sensitive people. Enjoy it with your eyes: wild orchids should never be picked or dug up, and they rarely survive being moved.
Plants That Are Poisonous to Eat
These plants are only dangerous when swallowed. The two hemlocks are among the most poisonous plants in North America. Teach children never to eat any wild plant, berry or root without an adult who knows it.
Spotted Water Hemlock (Cicuta maculata)
Spotted water hemlock is a native plant of wet meadows, marshes, ditches and stream banks across Michigan, and it is often called the most toxic plant in North America. It is 3 to 7 feet tall, with smooth stems streaked or blotched with purple, leaves divided into narrow, toothed leaflets, and flat-topped white flower clusters in summer. Its roots are made of several thick tubers and contain cicutoxin, which causes seizures within 15 minutes to an hour of eating. A bite of root can kill an adult. Many poisonings happen when people mistake the root for wild parsnip or wild carrot.
Poison Hemlock (Conium maculatum)
Read our guide to Poison Hemlock
Poison hemlock is a European plant that has spread along roadsides, ditches and field edges, especially in southern Michigan. It is 3 to 8 feet tall, with a smooth, hollow stem covered in purple spots, lacy, fern-like leaves that smell musty when crushed, and umbrella-shaped clusters of small white flowers. It looks a lot like wild carrot (Queen Anne’s lace), but wild carrot has a hairy stem with no purple blotches. All parts contain coniine, which paralyzes the muscles, including those used for breathing. Wear gloves if you pull it: the main danger is eating it, but the sap can irritate skin.
Jack-in-the-Pulpit (Arisaema triphyllum)
Read our guide to Jack-in-the-Pulpit
Jack-in-the-pulpit is a native woodland wildflower, 1 to 2 feet tall, with one or two leaves of three leaflets each. In spring it has a hooded green or purple-striped flower (the “pulpit”), and in late summer a cluster of bright red berries. All parts are packed with needle-like calcium oxalate crystals. Biting into any part causes immediate, intense burning and swelling of the lips, tongue and throat. The pain usually stops people from swallowing much, but swelling of the throat needs medical attention.
Lily of the Valley (Convallaria majalis)
Lily of the valley is a European groundcover planted in many Michigan gardens that also spreads into nearby woods. It has two or three broad leaves and a stem of small, fragrant, white bell-shaped flowers in May, followed by orange-red berries. All parts contain cardiac glycosides that can slow or disrupt the heart. Small children are at risk from the berries. The plant is also dangerous for dogs and cats.
Autumn Crocus (Meadow Saffron) (Colchicum autumnale)
Autumn crocus is a garden bulb, not a wild plant, but it is grown in many Michigan yards. Its pink or lilac crocus-like flowers appear in September and October with no leaves. The broad leaves come up in spring and die back by early summer. All parts contain colchicine. Poisonings happen when the spring leaves are mistaken for wild leeks (ramps) or wild garlic, which grow in the same places at the same time of year. Symptoms start hours after eating, and severe cases can be fatal.
Northern Blue Flag (Iris versicolor)
Northern blue flag is a native iris of marshes, wet meadows and shorelines, 2 to 3 feet tall, with sword-shaped leaves and violet-blue flowers veined with white and yellow in early summer. Its thick underground stems (rhizomes) are the most toxic part. They cause burning, nausea, vomiting and diarrhea if eaten, and the sap can irritate skin. Before it flowers, its leaves can be confused with cattails or sweet flag.
Periwinkle (Vinca minor)
Periwinkle (also called myrtle) is an evergreen groundcover from Europe with small, glossy, oval leaves and five-petaled blue-violet flowers in spring. It was planted around homes and cemeteries for generations and now carpets many Michigan woodlots, where it crowds out native wildflowers. It contains alkaloids that can cause vomiting and diarrhea if eaten. It is more of a concern for dogs and cats than for people. Don’t confuse it with Madagascar periwinkle (Catharanthus roseus), a different and more toxic annual bedding plant.
Wild Ginger (Asarum canadense)
Wild ginger is a low native groundcover of rich woods, with pairs of velvety, heart-shaped leaves and a single brownish-purple flower hidden at ground level in spring. Its rhizome smells and tastes like ginger and was once used as a spice. It contains aristolochic acid, which damages the kidneys and is linked to cancer, so don’t use it in cooking or herbal teas. Touching the plant is harmless for most people, but the leaves can cause a mild rash in sensitive skin.
Plants That Mainly Harm Pets and Livestock
Wild Garlic (Meadow Garlic) (Allium canadense)
Wild garlic is a native plant of meadows, lawns and open woods, with narrow, grass-like leaves, a strong onion smell and a head of small pink or white flowers, often mixed with little bulblets. It is edible for people, like onions and chives, but all Allium species damage red blood cells in dogs and cats. The smell is the safety check. If a plant looks like wild garlic or wild onion but doesn’t smell of onion, don’t eat it: it may be death camas, which is deadly.
Field Horsetail (Equisetum arvense)
Field horsetail grows in damp ditches, rail beds and field edges. In spring it sends up pale brown fertile stems topped with a cone, followed by green, bottlebrush-like stems with whorls of thin branches. It contains thiaminase, an enzyme that destroys vitamin B1. Horses that eat it in hay over several weeks can develop weakness, staggering and weight loss. It is not a meaningful risk to people.
Sheep Sorrel (Rumex acetosella)
Sheep sorrel is a common weed of poor, acidic soil in lawns, pastures and gardens. It has arrow-shaped leaves with two outward-pointing lobes at the base and spikes of tiny reddish flowers. The leaves have a sour, lemony taste from oxalic acid. They are safe to eat in small amounts in salads, but sheep and cattle that graze a lot of it can be poisoned.
Buckwheat (Fagopyrum esculentum)
Buckwheat is a crop and cover crop, 2 to 4 feet tall, with heart-shaped leaves, reddish stems and clusters of small white flowers. Animals that eat a lot of it can become sensitive to sunlight (fagopyrism): pale-skinned pigs, sheep and cattle get skin reddening and swelling. For people, buckwheat flour is a food, but it can cause severe allergic reactions in those who are allergic to it.
What to Do After Contact or Poisoning
- Poison ivy or sumac: wash the skin with soap and cool water as soon as possible, ideally within 10 to 30 minutes, and wash clothes, gloves and tools separately. See a doctor if the rash covers a large area or reaches the face, eyes or genitals.
- Hogweed or wild parsnip sap: wash the skin right away with soap and water and keep it covered from sunlight for at least 48 hours. If sap gets in the eyes, rinse them with water and get medical help.
- Swallowed any plant on this list: call Poison Control at 1-800-222-1222. Keep a sample or photo of the plant for identification. Don’t wait for symptoms after eating hemlock, water hemlock or autumn crocus: call 911.
- Pets: call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435.
Not on this list: poison oak (Toxicodendron diversilobum) grows only along the Pacific coast, and maidenhair fern and carrion flower (Smilax herbacea), which older lists include, are not meaningfully poisonous.
Related: Poisonous Plants Guide · Poisonous Plants in Ohio
