Nettle family (Urticaceae)
Description: This herbaceous perennial plant is about 2-4' tall and either branched or unbranched. The stems are light to medium green and abundantly covered with stiff white hairs that have the capacity to sting when they are rubbed against. The lower to middle leaves are alternate, while the upper leaves are opposite. These leaves are up to 6" long and 4" across; they are medium to dark green, ovate-cordate to oval-ovate in shape, and coarsely serrated or serrated-crenate. Young leaves are densely hairy and wrinkled in appearance, while older leaves become less hairy and wrinkled with age. Leaf venation is pinnate. The petioles are up to 4" long and abundantly covered with stinging hairs, like the stems. The leaves may have a few stinging hairs as well, particularly along the central veins of their undersides. Some plants have a tendency to loose many of their stinging hairs as the season progresses. Individual plants are either monoecious (separate male and female flowers on the same plant) or unisexual.
The male flowers occur in branching cymes from the axils of the leaves. These cymes spread outward from the stem and they are about the same length as the petioles of the leaves. Each male flower is greenish white to white and less than 1/8" (3 mm.) across, consisting of 5 narrow sepals, 5 stamens, and no petals. The female flowers occur in branching cymes toward the apex of the plant. These cymes are erect to spreading and 4" or more in length. Each female flower is more or less green and about 1/8" (3 mm.) across, consisting of 4 sepals of unequal size (2 large and 2 small) and an ovary with a long style. The blooming period usually occurs during mid- to late summer. The flowers are wind-pollinated. Each female flower is replaced by a small dry fruit that is curved and ovoid in shape. This plant often forms colonies of variable size.
Cultivation: The preference is partial sun to medium shade, moist conditions, and a fertile loamy soil with abundant organic matter. Because of its stinging hairs and tendency to spread, you probably would not want to cultivate this plant near the house, except possibly as a privacy barrier.
Range & Habitat: The native Wood Nettle is common in central and northern Illinois, but it is uncommon or absent in parts of southern Illinois (see Distribution Map). Habitats include moist floodplain woodlands, moist bottomland woodlands, mesic woodlands, shady seeps, and other moist places in wooded areas. Various deciduous trees (e.g., elms, maples, or sycamore) dominate the habitats where the Wood Nettle occurs.
Faunal Associations: The caterpillars of the following butterflies feed on the foliage: Polygonia comma (Comma), Polygonia interrogationis (Question Mark), and Vanessa atalanta (Red Admiral). Other insect feeders include caterpillars of the moths Bomolocha edictalis (Large Bomolocha) and Bomolocha sordidula (Sordid Bomolocha), leaf-mining larvae of the fly Agromyza subnigripes, and the stink bug Proxys punctulatus. White-Tailed Deer also browse on the foliage of Wood Nettle occasionally, notwithstanding the stinging hairs. When this plant forms dense colonies in wooded areas, it provides valuable cover for wildlife.
Photographic Location: A floodplain woodland in Vermilion County, Illinois. The Wood Nettle in the photographs wasn't in bloom.
Comments: This native plant is often mistaken for the introduced Urtica dioica (Stinging Nettle). Both species have stinging hairs and a similar appearance. However, the Wood Nettle has some alternate leaves, while Stinging Nettle has pairs of opposite leaves only. There are also differences in the characteristics of their flowers. Another similar species, Boehmeria cylindrica (False Nettle), also has opposite leaves, but it lacks stinging hairs altogether. Like other members of the Nettle family, the Wood Nettle lacks showy flowers because they are wind-pollinated, rather than pollinated by insects. Some people may regard this species as an undesirable woodland weed because of its stinging hairs and unassuming appearance, but it is an important host plant of some native butterflies.