Wisconsin has 9 species of horsetails or scouring rushes. All horsetails have green, jointed stems, with a hollow center and prominent ridges between the nodes. At each node small scale-like leaves are
fused into a sheath around the stem. The stems are rough from the silica that collects in the cell walls of the outer skin -- the origin of “scouring” rush.
All horsetails are perennial and spread by underground stems or rhizomes.
Origin of the name: Equisetum: equis, L., horse; seta, L., bristle. Refers to the coarse black roots of some horsetails.
Most horsetails are plants of moist places, with near neutral or slightly acid soil.
Common horsetail tolerates a much wider range of conditions and grows almost anywhere -- along roads, in pastures and woods, in sun or shade and in very wet to very dry soil. Common Horsetail also tolerates more disturbance than the other Equisetum.
Like some of the other horsetails, and the closely related ferns, the aerial stems of Common Horsetail are dimorphic -- there are two kinds.
The sterile or vegetative stems are green, branched and have a hollow center about 1/4 to 1/3 the diameter of the stem. The branches are whorled at each node and point upward. The fertile (spore bearing) stems lack chlorophyll, and so are pink or tan, and unbranched. The spores are in a cone at the tip. The sterile stems die back to the rhizome after a hard frost; the fertile stems die back in the summer after releasing the spores.
Aerial stems in all horsetails vary considerably in height and branching under different environmental conditions. E. arvense stems are usually no wider than 5 mm and have 10 to 14 ridges.
The teeth on the sheath are dark brown, longer than wide and with white margins visible with a lens.
arvense, L., growing in cultivated fields
Range: N. America, to n TX, LA, FL; Eurasia
WI Range: Statewide
Common associates: Sugar maple, bluegrass, yarrow
Wetland Indicator Status: FAC
Coefficient of Conservatism: C = 0 (S&W), C = 0 (MI)