Poison ivy identification: leaves, vines, berries and look-alikes

Eastern vs western poison ivy, poison oak and poison sumac

All of these are Toxicodendron species, and all carry urushiol, the oil behind the rash. Names below follow the USDA PLANTS Database and NC State Extension.

• Eastern poison ivy (Toxicodendron radicans): the climbing, hairy-vined plant described above. CDC/NIOSH calls it typically a hairy, ropelike vine with three shiny green leaves budding from one small stem.
• Western poison ivy (Toxicodendron rydbergii): CDC/NIOSH describes it as a low shrub that does not form a climbing vine. Use the leaflet and arrangement checks; there is no hairy vine to find.
• Atlantic poison oak (Toxicodendron pubescens): the FDA describes a low shrub of the Eastern and Southern United States with fuzzy green leaves in clusters of three, lobed or deeply toothed with rounded tips. Alabama Extension gives upright stems to about 3 feet on dry sites; MDC says it does not climb, makes no aerial roots and has berries with inconspicuous hairs.
• Pacific poison oak (Toxicodendron diversilobum): the FDA says it grows in tall clumps or long vines on the Pacific Coast.
• Poison sumac (Toxicodendron vernix): a shrub or small tree with 7 to 13 smooth-edged leaflets per leaf (FDA; Alabama Extension counts up to 15), stems and leaf stalks that are often bright red (Alabama Extension), and glossy, pale yellow or cream-colored berries (CDC/NIOSH). It grows in wet ground: bogs and swamps in the Northeast, Midwest and parts of the Southeast (FDA).

Poison ivy vs poison oak, in one line: poison ivy climbs or trails with hairy aerial roots and has glossy leaflets; poison oak stands as a low, upright shrub (on the Atlantic side) with fuzzy, round-lobed leaflets (FDA) crowded near the tips of its stems (Alabama Extension). In a photo they can look alike; the habit and the hairs usually decide it.

Poison ivy look-alikes and the test for each

Brandywine Conservancy and Alabama Extension both note how often harmless plants get blamed. Alabama Extension's rule is the one to keep: if you're not sure, don't touch it.

Two more that catch people: climbing hydrangea (Decumaria barbara) has a hairy vine much like poison ivy, but its leaves are simple and opposite (Alabama Extension); and mock strawberry (Duchesnea indica), a lawn weed with yellow flowers, has three leaflets that join at one point, without the long middle stalk (Brandywine). For the low three-leaflet plants in turf, such as clover, wood sorrel and black medic, see the lawn weed identification guide.

Urushiol: what the health agencies say

These lines are as CDC/NIOSH, the FDA and the AAD state them. They are not medical advice.

• Every part, every season. The American Academy of Dermatology says touching any part of these plants, including the roots, can cause a rash, even during the winter, and that the plants are poisonous year-round.
• Never burn it. CDC/NIOSH says not to burn plants that may be poison ivy, poison oak or poison sumac, because inhaling the smoke can cause severe allergic respiratory problems.
• It lingers on things. CDC/NIOSH says urushiol can stay active on the surface of objects for up to 5 years. The FDA notes the oil can stick to pets' fur and cause a reaction in whoever pets them; the AAD suggests bathing a pet you suspect has been near these plants, wearing rubber gloves. For plants dogs might chew, see plants poisonous to dogs.
• The rash itself isn't contagious. The FDA says these rashes can't be spread from person to person; the oil, while still on skin, clothes or tools, can.

If you touched it: first steps and when to get help

First steps. The FDA says to wash your skin in soap and cool water as soon as possible. CDC/NIOSH says to rinse skin immediately with rubbing alcohol, poison plant wash or dishwashing soap and lots of water, and to scrub under your nails with a brush. Wash the clothes, gloves and tools that touched the plant.

See a doctor, according to the FDA, if you have a temperature over 100°F; there is pus, soft yellow scabs or tenderness on the rash; the itching gets worse or keeps you awake; the rash spreads to your eyes, mouth or genital area, or covers more than one-fourth of your skin; the rash is not improving within a few weeks; or the rash is widespread and severe. CDC/NIOSH adds: get medical help in severe cases or if the rash is on the face or genitals.

Emergency care. CDC/NIOSH says to call 911 or go to a hospital emergency room for a severe allergic reaction, like swelling or difficulty breathing, or if the person has had a severe reaction to poisonous plants in the past. The FDA also lists difficulty breathing as a reason to see a doctor.

Removing it, and where it grows

If poison ivy has to go, follow the label and local rules for any product, or ask your county extension office. Don't burn it, and keep in mind that Alabama Extension warns trimming or mowing patches can make particles of the allergen airborne. Wear long sleeves, gloves and closed shoes, and wash everything afterwards.

Poison ivy is native to North America: NC State says throughout the United States and much of southern Canada, and USDA PLANTS lists eastern and western poison ivy as native to the lower 48 states and Canada. The FDA says poison ivy is absent from Alaska, Hawaii and parts of the West Coast. The sources here describe no wild populations in Britain or continental Europe; in the UK the RHS lists Toxicodendron as the only plant in category A, its most toxic group, of potentially harmful garden plants. What most British readers call ivy is English ivy, a different plant with simple, lobed leaves.

To keep track of a patch you want to avoid next season, Plant Identifier's Plant Map records where each located identification was made. For unknown plants in general, start with how to identify plants.