Steer Clear of Two Common Poisonous Plants—Here’s How

A plant with bright green stems and tiny yellow flowers; a plant with red fuzzy leaves

Left: Wild parsnip head. Right: Poison ivy leaves may be red early in the spring.

In Chicagoland, summertime means getting outside and enjoying the many parks and green spaces the city has to offer. While enjoying them, keep your eyes open for a few plants that are a little deceptive—they look harmless but could cause discomfort. Here’s what you need to know about two plants common to the Midwest:

Wild Parsnip (Pastinaca sativa): It may sound appetizing, but keep your distance.  

Although it seems innocent, with bunches of dainty yellow flowers, wild parsnip is harmful to the touch. It’s in the same family as carrots, and while its root may be edible, the plant tissue above ground contains a toxic sap. If it touches your skin, this sap can cause a rash that worsens with sun exposure. 

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Green leaves with jagged edges
Wild parsnip leaves.

How to spot this plant: Wild parsnip can grow two to five feet tall, and it’s mostly found in disturbed areas, like on the sides of roads and where soil has been moved. It typically blooms from May to July, with yellow flowers on the top of the plant that form a flat cluster (later, these turn into brown seeds). The stem has ridges, and the leaves are large and compound with at least eight notches (called “teeth”) on a large leaflet—they look like supersized parsley leaves.

Lookalikes: From far away, wild parsnip flower might resemble dill. As you examine it more closely, the leaves begin to look more parsley-like. Wild parsnip also resembles a native plant called golden Alexanders, which is smaller in size and has fewer teeth on the leaflets. Its seed formation (umbel) is more elliptical in shape compared to the flat-topped parsnip.

How to avoid it: Wear long sleeves and pants and walk on clear trails to avoid touching vegetation. If you suspect you’ve come into contact with wild parsnip, be sure to clean the area and stay out of the sun—exposure to sunlight can cause blistering and scarring.

What’s next: As more habitat destruction happens, we might see more wild parsnip cropping up. When soil is exposed and the plant faces little competition, it can move in. Once established, wild parsnip spreads quickly. Habitat restoration efforts can help curb wild parsnip, and you can join The Field Museum in restoring local nature areas. 

Poison Ivy (Toxicodendron radicans): Even the scientific name gives me the chills!

“Leaves of three, let them be” is a saying you probably learned as a child (but I’ll add a little correction to it, as it is three leaflets, or parts of a leaf). Poison ivy produces an oil that will irritate most people’s skin and cause a minor to major reaction. 

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Large, thin and pointed green leaves
Poison ivy leaves.

How to identify the plant: Look for an herbaceous (flower-like) plant with three leaflets and a vine that may appear fuzzy. Early in the spring, poison ivy has a reddish tint to its leaves, and the red often stays on the stems of the leaflets throughout the season. Poison ivy likes some shade and a little moisture, but it has been found in drier woodlands as well. 

Lookalikes: Many things seem to look like poison ivy at first: in a wooded area, raspberry leaves can seem very similar (but they’ll be on a stem with thorns, and the stem might have a purple hue to it). If you are looking at vines, other plants will have five leaflets or simple leaves—one entire leaf.

How to avoid it: Cover up, making sure your socks cover the area between your boot and pant leg. After walking through an area with poison ivy, avoid touching the exterior of your clothing. If you suspect you’ve come into contact with poison ivy, wash the area as soon as you can, and definitely don’t scratch. If the rash appears to worsen or spread, see a doctor. It’s not common to have a bad reaction to poison ivy the first time around, but if you’ve been exposed many times, you’ll want to be extra careful—repeat exposures can increase your skin’s sensitivity to urushiol, the oily chemical poison ivy produces.

What’s next: Poison ivy responds very well to increased levels of carbon in the atmosphere. This means that, with climate change, we will be seeing more of it.

But don’t let these plants deter you from enjoying the outdoors and nature. When you become more familiar with the environment around you, staying outside can bring more joy, less fear, and an overall appreciation for our local nature.

Iza Redlinski is a Conservation Ecologist in the Keller Science Action Center.

The Field Museum doesn’t give medical advice. If you experience a reaction to these or any other plants, please consult a doctor.