Heartleaf Nettle, Fireweed

Urtica chamaedryoides



A common, erect (most plants ~12” high); greenish to red square-stemmed very green forb.  It has long-petioled, opposite, ovate, leaves with serrated margins. Stinging hairs are present on leaf and stem surfaces and virtually all plant parts.  Their structure is a bulbous base containing an irritating substance and a brittle, sharp shaft which injects the toxin upon touch.  It can cause a painful irritation lasting several days. The flowers lack colorful petals since it is a wind-pollinated species.  Thus the axillary globular flower-heads are rather inconspicuous but their four sepals do have stinging hairs.  The plant can be monoecious or dioecious. Heartleaf Nettle is a host plant for Red Admiral and Question Marks as well as Painted Lady, Eastern Comma, and Mourning Cloak butterflies. Its tiny seeds are sticky and probably adhere to passing animals as a dispersal mechanism. It generally disappears with the coming of summer temperatures.


Prefers moist, shaded, rocky sites.

Toxic Agent

Histamine, acetylcholine, serotonin

Signs of Livestock Ingestion

Cattle will generally avoid Heartleaf Nettle.

Management Strategies

This species will die back naturally in hot weather.