Nettle family (Urticaceae)
Description: This native annual plant is ½2' tall, branching occasionally in the upper half. The stems are smooth, round, hairless, and translucent. They are light green, greyish green, or reddish green in appearance; some of the large stems may be slightly ribbed. The opposite leaves are 1-5' long and half as much across. They are ovate, hairless, and coarsely serrated. Each leaf has a thin membranous texture with a prominent central vein and two conspicuous side veins. The upper surface is green or dark green, while the lower surface is light green or nearly white. The petioles of the leaves are quite long, frequently 1" in length or more. From the axil of each upper leaf, there develops a narrow raceme of flowers up to 1" long. This raceme is usually shorter than the petiole, slightly curved, and more or less horizontal. Each plant has separate male and/or female flowers that are less than 1/8" long, and either greenish white or greenish yellow. The male flowers have no petals, 4 sepals, and 4 stamens, while the female flowers have no petals, 3 sepals, and 1 pistil. Toward the inner surface of the sepals are small scales. The blooming period occurs from mid-summer to early fall, and lasts about 1-2 months. There is no floral scent. The tiny achenes are green, sometimes with black stripes. They can be blown about by the wind, and in this manner are dispersed.
Cultivation: The preference is light shade and moist to wet conditions. This plant usually grows in rich woodland soil. The foliage is little bothered by disease and is quite attractive. Standing water is tolerated if it is temporary.
Range & Habitat: Clearweed is a common woodland plant that occurs in almost all counties of Illinois (see Distribution Map). Habitats include poorly drained areas of upland forests, floodplain forests, crevices in rocky canyons, and shady or partially shaded wetland areas, including seeps, borders of small streams, and alongside pools of water. The moist wooded areas where this plant occurs are typically dominated by such deciduous trees as Silver Maple, Sugar Maple, Sycamore, River Birch, Green Ash, etc. Clearweed often forms large colonies by reseeding itself.
Faunal Associations: The flowers are wind-pollinated, therefore they don't attract many insects. The caterpillars of the following butterflies feed on the foliage: Nymphalis milberti (Milbert's Tortoiseshell), Polygonia comma (Comma), Polygonia interrogationis (Question Mark), and Vanessa atalanta (Red Admiral). These caterpillars feed on other members of the Nettle family as well.
Photographic Location: The plants were growing in a shady area along a small stream at Meadowbrook Park, Urbana, Illinois.
Comments: The most unusual characteristic of this plant is the translucency of the foliage this has been useful in biology classes to show the uptake of liquids from the roots into the stems and leaves. A less common species of Clearweed, Pilea fontana, has stems that are less translucent and its achenes are black, rather than green. Clearweed resembles other members of the Nettle family as well, but it lacks the stinging hairs that can be found on Urtica dioica (Stinging Nettle) and Laportea canadensis (Wood Nettle). While Boehmeria cylindrica (False Nettle) lacks stinging hairs, its stems aren't translucent and its racemes of flowers are more erect and longer than Clearweed's racemes.