**Description:** A tall perennial herb with serrated, heart-shaped leaves and stems covered in tiny, hollow hairs that act like glass needles.
**Size:** Can reach heights of 3 to 7 feet.
**Wildlife Value:** Important food plant for Red Admiral butterfly caterpillars. The hairs inject formic acid into the skin, causing a painful sensation.
**Identification:** Features square stems and opposite leaves. Boiling removes the sting, making the leaves a nutritious wild green.
**Habitat:** Found in rich, moist soils along river banks and forest trails.