Many people are learning the hard way how dangerous it can be.
Waterloo man Nick Zander says he was walking in a ditch after fishing. Later, he saw blisters on his arm, and now he may have permanent scars on his arm.
He had run into some wild parsnip. The weed has been around for years, but this year it's spreading across Iowa. It can be spotted along many ditches and side roads.
When someone's skin comes into contact with the plant's sap, the chemicals in the sap can interact with sunlight and cause anything from blisters, to a rash, to a burning sensation.
Black Hawk County Conservation says the best thing people can do is learn how to recognize the plant and avoid it.
They say if someone does come into contact with the plant's sap and starts to feel a reaction, they should try to avoid the sunlight and make sure to keep the affected area clean.
This information is especially important for people planning to participate in RAGBRAI in just two weeks. The organization tweeted out that there is a lot of wild parsnip along the bike route this year.