Hiking, mountain biking, birding, or generally recreating in the woods comes with great rewards—and a few hazards. For one thing, plants, while mostly harmless and massively beneficial for their oxygenating, shade-providing splendor, can be poisonous. More than one hiker has made the mistake of using a few leaves of poison oak as backcountry toilet paper. (Yikes.) And it’s not uncommon to be strolling about through a meadow, only to find you’ve wandered into a patch of stinging nettles. (Ouch.)

But, without being a horticulture whiz, how can you tell which plants are poisonous, and which are not? Follow the guidance outlined below to experience the Great Outdoors with great outdoor worries.

Leaves of Three

You’ve likely heard this before: “Leaves of Three, Let it Be.” The saying applies to both poison oak and poison ivy. Both have urushiol on their leaves and in their sap, which can cause a terrible, itchy rash when it contacts human skin. If you’re on trails where you know poison oak or ivy exist, consider wearing protective clothing. And if your clothes or body become contaminated, plan on thoroughly washing them as well as any exposed skin within two hours to mitigate the resin. Cleansers specific to removing urushiol, like Tecnu or Zanfel, are especially effective if you’re highly allergic or on trail for extended periods of time. Adding some of these wipe packets to your kit will help wipe skin as soon as it’s contacted either plant.

Poison Oak

Found mostly in the western United States, poison oak is a member of the sumac family. It grows as a woody vine or shrub. Poison oak leaves (which grow in clusters of three) range from yellowish green to dark red. The leaves of this plant are scalloped on the edges.

Poison Ivy

While poison oak is commonly found in the West, poison ivy is found mostly in the eastern United States. Its leaves range from bright green to red and are almond-shaped, and they come to a point. Poison ivy leaves are also grouped in threes.

Other Plants that Cause Itchiness

Poison Sumac

Found mostly in the eastern United States, like its friend poison ivy, poison sumac grows as a woody shrub with greenish red, oval-shaped leaves that come to a sharp point at the end. These leaf clusters don’t come in threes. The stems are a dark reddish-brown color, and there are sometimes small white clusters of flowers growing off the stem on light green stems of their own. Sumac is more poisonous than poison oak or ivy, especially when the plant is burned. 

Pokey, Stinging Plants

Cacti

This one’s fairly obvious, but cacti can hurt. The spines on cacti are meant to protect the plants from animals that might want to eat them. They also trap water and air for the plant, and create shade. And yes, they also can become lodged in your skin and hurt. (It’s a good idea to keep sharp-nosed tweezers in your pack. Duct tape can also work for removing small spines.) Stay away from obviously pokey plants.

Stinging Nettle

Don’t be fooled by the “soft” look of nettle plants. Tiny, hair-like protrusions called “tricomes” inject histamine and other chemicals into human skin when touched, which causes…well, stinging. To identify stinging, or common nettles, as they’re also referred to, keep an eye out for plants that look like mint plants and appear to be soft, with leaves that have serrated edges. Stinging nettle plants have small greening-brownish flowers. They grow close to the ground, mostly in meadows, in the winter, and grow tall in the summer. 

Poison Hemlock

This plant killed Socrates, and it could kill you, if ingested. Every part of the hemlock plant is poisonous, especially when eaten. But it’s also poisonous to the touch, and when its fragrance is inhaled. Identify it by its purple spots on green leaves, sometimes with clusters of small white flowers. Don’t be fooled by its beauty.

Poisonous To Eat

Along with the numerous species of mushrooms that can kill you (growing alongside the mushrooms that are like striking culinary gold in the wild), a host of plants and their petals or berries are also poisonous. Stay away from Snowberries, Bittersweet, Buttercups, Manchineel, Pokeweed, and Deadly Nightshade (the name of that last one should give it away).

Apps

How do you know what you’re looking at in the wild? Aside from studying a giant book of horticulture or scanning the web every night before bed, your best bet is downloading an app or two; plenty of great options exist to help you identify plants in the field, should you be carrying your smartphone. Check out the following, and download one or two. Having the brains of an app can save you from itchy, pokey, and even deadly encounters with poisonous plants. But remember, if in doubt, let it be.

Pl@ntnet

An app for identifying, exploring, and sharing about plants: identify.plantnet.org

INaturalist

Sort of a crowd-sourced science hub for naturalists: inaturalist.org

LeafSnap

An electronic field guide used by researchers: leafsnap.com

Picture This

Identifies flowers, leaves, herbs, plants: picturethisai.com

Smartplant

Plant care and identification, as well as the ability to chat with experts: smartplantapp.com

Plantsnap

Identify plants, cacti, succulents, and mushrooms in seconds: plantsnap.com

All articles are for general informational purposes.  Each individual’s needs, preferences, goals and abilities may vary.  Be sure to obtain all appropriate training, expert supervision and/or medical advice before engaging in strenuous or potentially hazardous activity.