Urtica chamaedryoides aka Heart Leaf Nettle

Urtica chamaedryoides belongs to the nettle family. It is an annual, which lives for one year. Common names include heartleaf nettle, weak nettle, and fireweed. Its native range spans the central and southeastern United States to Guatemala. It grows in rich woods and on floodplains. It also grows on ground that people have disturbed. In Florida, it grows near farms and in pastures too. There, it grows through winter and often dies by May.

Plants stand about 0.3–1.6 feet (0.1–0.5 metres) tall, sometimes more. Weak stems branch near the base. They may lean on nearby plants. The stems are square and green to red. Leaves grow in pairs on opposite sides of the stem. They are heart-shaped or shaped like a triangle, with coarse teeth. Leaves shrink toward the stem tips. Small deposits of calcium carbonate mark the leaf surfaces. These deposits are called cystoliths. Stinging hairs cover stems, leaf stalks, and leaves. In shade, plants grow longer stems and larger leaves. Their flower clusters are looser too. In exposed sites, plants stay smaller, with a tighter form.

Tiny green to whitish flowers form round groups at leaf joints. Each group holds both male and female flowers. Wind carries the pollen. NC State gives the bloom time as March to November. The Florida account says spring through summer. Male flowers have five stamens, whose pollen sacs, called anthers, burst open. Each female flower has one ovary. Four or five sepals sit below it. The fruit is a small, flat, brown achene. It is egg-shaped, and calyx lobes enclose it.

This nettle grows in sun or part shade. It suits moist soil that drains well, including clay and loam. NC State lists a moderate growth rate and low upkeep. Growers can raise it from seed. It has value in meadows and native plant gardens. It also has value in butterfly gardens. Red admiral and eastern comma caterpillars eat its leaves. Mourning cloak and question mark caterpillars eat them too. Yet it can become a troublesome pasture weed. Mowing does not control it and may spread its sticky seeds.

The main risk is its sting. This can cause a painful skin rash. The effects range from brief itching to pain lasting two days. Contact can make horses very ill. In extreme cases, horses have died. NC State lists prepared leaves and stems as edible before bloom. It says they taste like spinach. It lists several ways to prepare them that reduce the sting. Florida's account lists no economic uses for this species. NC State also notes stem fibre for clothes. It records past use as medicine too. These accounts differ, so treat food and medicinal claims with care.