Did you know that a wetland plant in the carrot family contains one of the most potent toxins in North America? And it’s one that you—or animals under your care—could easily encounter.

Even a minute amount of the poison in water hemlock is enough to cause uncontrollable seizures and death in a person, pet or farm animal. Any part of the plant is poisonous, but the roots—which can be exposed by plowing or erosion—are especially toxic. They also happen to be tastiest to grazing cattle and horses. Even dogs have been known to chew on the plant with fatal results.

Water hemlock, which is found mainly in wet meadows or along streambanks in the western United States, usually starts growing in the early spring. So be on the lookout for a thick-stalked plant with tiny white blossoms. It’s one you’ll want to avoid.