Equisetum hyemale L. var. affine (Engelm.) A.A. Eaton — Overview

Rough Horsetail learn more about names for this taxon

Comprehensive Description

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This perennial plant is 2-5' tall, producing both fertile and infertile shoots. Each shoot has a single central stem that is jointed, unbranched, more or less erect, and ¼–¾" (6-18 mm.) across. The central stem is medium green, olive-green, or dark green, rough in texture, and evergreen. The individual joints that make up the central stem are up to several inches long; the upper joints are usually shorter than the lower joints. The stem joints have about 15-40 fine longitudinal ridges. At the conjunctions of adjacent joints, there are appressed ring-like sheaths up to ¾" long. Except along their upper and lower rims, the sheaths are whitish grey, brown, or black. The lower rims of these sheaths are usually black, while their upper rims have 15-40 tiny black teeth (scale-like leaves). These teeth are semi-deciduous and they often break off the sheaths with age. The interior cavity of the central stem is quite large, spanning at least two-thirds of its diameter. The central stem of each fertile shoot terminates in a spore-bearing cone up to 2" long on a short stalk. This cone is ovoid to broadly ellipsoid in shape, and it has a short narrow point at its apex. The cone is densely covered with rows of spore-bearing tubercles; it is usually pale yellow or pale reddish yellow. Instead of a single terminal cone, sometimes an older shoot will produce 1-4 spore-bearing cones on short lateral stalks just below its terminal joint. Infertile shoots are very similar to fertile shoots, except they lack spore-bearing cones. 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. Cultivation


Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© John Hilty

Source: Illinois Wildflowers


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