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DescriptionThis native perennial plant is 3-7' tall and usually unbranched, although short stems may develop from the leaf axils. The central stem is light green and stout; it has several flat ridges that are separated by narrow channels. The central stem is sparsely covered with stiff white hairs of variable length; these hairs can penetrate the skin and sting. Along the central stem are pairs of opposite leaves that droop downward slightly. The leaf blades are up to 8" long and 2½" across; they are medium to dark green, lanceolate, and coarsely serrated. The base of each leaf blade is rounded or slightly cordate. The upper surface of each leaf blade is heavily veined and glabrous, while the lower surface has sparse stiff hairs that can also sting. The slender petioles of the leaves are up to 1" long. At the base of each petiole, there is a pair of stipules up to ½" long. Panicles of flowers develop from the axils of the middle to upper leaves. These panicles are much branched and droop downward; their pubescent branches are heavily covered with flowers. Slender Nettle is monoecious to slightly dioecious; some plants have male flowers entirely or predominantly, while other plants have female flowers entirely or predominately. The male flowers are 1/8" across with 4 green sepals and 4 white stamens. The female flowers are 1/8" across with 4 green sepals; the 2 inner sepals that enclose the ovary are larger in size than the 2 outer sepals. The sepals of both male and female flowers are pubescent; neither kind of flower has petals. The blooming period occurs during the summer and can last 1-2 months for a colony of plants. Pollination of the flowers is by wind. The brown seeds are 1.01.5 mm. long and irregular in shape. They can remain viable in the ground for 10 years. The root system is fibrous and rhizomatous. Vegetative colonies are often produced from the long rhizomes.