Visual reference

Dangerous plants of North America

A side-by-side photo guide to the harmful plants most likely to ruin a hike, a garden day, or a backyard cleanup. Bookmark this page so you have it on hand the next time you're not sure what you're looking at.

Not a substitute for expert identification. If a plant could be water hemlock or manchineel, don't touch or taste it. When in doubt, snap a photo and run a free check.

High danger

Poison Ivy

Toxicodendron radicans / rydbergii

Causes blistering rash from urushiol oil.

Range: Throughout the contiguous US and southern Canada

Habitat: Forest edges, fence lines, riverbanks, backyards

How to identify

Three pointed leaflets per stem (middle leaflet on a longer stalk)
Leaves shiny in spring, dull green in summer, red/orange in fall
Grows as a low shrub, ground cover, or hairy climbing vine
Clusters of small white-ish berries in late summer

Itchy red rash and blisters appearing 12–72 hours after contact.

High danger

Poison Oak

Toxicodendron diversilobum / pubescens

Same urushiol oil as poison ivy.

Range: West Coast (Pacific) and Southeast (Atlantic)

Habitat: Dry woodlands, chaparral, oak forests, coastal scrub

How to identify

Three leaflets with rounded, lobed edges resembling small oak leaves
Often glossy, sometimes fuzzy underneath
Grows as a dense shrub or climbing vine
Bright red foliage in fall, bare stems in winter

Same blistering, itchy rash as poison ivy.

High danger

Poison Sumac

Toxicodendron vernix

Often considered the most potent of the three urushiol plants.

Range: Eastern US, especially the Southeast and Great Lakes

Habitat: Swamps, bogs, wet woodlands — almost always near standing water

How to identify

7 to 13 smooth-edged leaflets in pairs along a red stem
Tall woody shrub or small tree (5–20 ft)
Drooping clusters of small white or gray berries
Brilliant red-orange foliage in autumn

Severe blistering rash; smoke from burning plants is dangerous to inhale.

Extreme danger

Water Hemlock

Cicuta maculata

Considered the most toxic plant in North America — fatal if ingested.

Range: All US states and most of Canada

Habitat: Wet meadows, marshes, ditches, streambanks

How to identify

Small white flowers in umbrella-shaped (umbel) clusters
Smooth, hollow green stem with purple streaks or blotches
Narrow, lance-shaped leaflets with sharp serrated edges
Thick tuberous roots that smell like raw parsnip when cut

Ingestion causes violent seizures within 15–60 minutes and can be fatal. Never taste, chew, or handle the roots without gloves.

High danger

Giant Hogweed

Heracleum mantegazzianum

Sap causes severe burns and permanent scarring in sunlight.

Range: Northeast, Mid-Atlantic, Pacific Northwest, Great Lakes

Habitat: Roadsides, streambanks, abandoned lots, riparian areas

How to identify

Towering plant, 8–14 ft tall when flowering
Massive white umbrella-shaped flower clusters up to 2.5 ft wide
Thick green stem with purple blotches and stiff white bristles
Enormous deeply lobed leaves up to 5 ft across

Sap on skin reacts with sunlight (phytophotodermatitis) within 15 minutes, causing painful burns, blisters, and dark scarring that can last years. Eye contact can cause blindness.

Moderate danger

Wild Parsnip

Pastinaca sativa

Sap causes painful sun-triggered burns.

Range: Most of the US and southern Canada

Habitat: Roadsides, prairies, pastures, disturbed ground

How to identify

Flat-topped clusters of small yellow flowers
Tall (2–5 ft) grooved green stem
Compound leaves with toothed, mitten-shaped leaflets
Smells like parsnip when crushed

Sap plus sunlight produces red blisters and brown scarring 24–48 hours after exposure.

Moderate danger

Stinging Nettle

Urtica dioica

Hair-like needles inject irritating chemicals on contact.

Range: Throughout the US and Canada

Habitat: Moist woodlands, streamsides, gardens, disturbed soil

How to identify

Heart-shaped leaves with deeply serrated edges, in opposite pairs
Square stems covered in fine stinging hairs
Tiny green-white flowers in dangling clusters
Grows 3–6 ft tall in dense colonies

Immediate stinging, burning, and itchy welts that usually fade within a few hours.

Extreme danger

Manchineel Tree

Hippomane mancinella

One of the most toxic trees in the world — every part is poisonous.

Range: Coastal South Florida, the Caribbean, and Gulf shorelines

Habitat: Sandy beaches, mangroves, brackish coastal areas

How to identify

Small evergreen tree (up to 50 ft) with a broad, spreading crown
Glossy oval green leaves with finely serrated edges
Small green fruit resembling miniature apples ("beach apples")
Often marked with red paint or warning signs in Florida parks

Sap causes severe blistering burns; eating the fruit can be fatal; even standing under the tree in rain can blister skin. Do not touch, eat, or burn.

Spotted one of these in the wild?

Get a free instant safety check — no signup, no app to install.

Check a plant now →