This native perennial plant is unbranched and 2-4' tall. It consists of a single central stem with multiple overlapping joints; the diameter of this stem spans up to ¾" across. The stems of Scouring Rush are green, olive-green, or dark green, rough in texture, and evergreen; they are usually erect. The joints that make up the central stem are individually several inches long; the upper joints are shorter than the lower joints. Each joint has about 10-40 fine ridges along its length. At the apex of each joint, there is an appressed ring-like sheath up to 1" long, from which the next joint develops. Except at its upper and lower rims, this sheath can be whitish grey, brown, or black; it is always black along the rim of its base, while its upper rim terminates in up to 40 tiny black teeth. These teeth are deciduous and often break off the stem. The interior cavity is quite large and spans at least one-half the diameter of a joint. Each fertile stem terminates in a spore-bearing cone up to 2" long on a short stalk. This cone is variably colored and usually pointed at the top. Infertile stems are very similar to fertile stems, except they lack spore-bearing cones. Secondary stems (branchlets) are rarely produced. The cones release their spores from late spring to mid-summer; they wither away later in the year. The root system consists of extensive rhizomes with fibrous secondary roots. This plant often forms dense colonies; sometimes these colonies can be quite large in size.