Equisetum arvense

Common horsetail is an herbaceous, non-flowering perennial in the Equisetaceae (horsetail) family.  It is native to temperate regions in the Northern Hemisphere and throughout the arctic.  It is widely distributed in Eurasia and most of North America except for the lower southeast U.S.  Common horsetail develops thick weedy stands of slender, upright, coarse, unbranched shoots up to 2 feet tall that, when bunched together, resemble a horse’s tail. It can be found in savannas, prairies, roadsides, arable land, ditches and disturbed areas. This plant develops deciduous fertile and infertile shoots.  It reproduces by spores produced on a light-brown cone at the tip of a non-photosynthetic stem in early to mid-spring.  Sterile (vegetative) green photosynthetic stems appear after the spore-bearing stems wilt, then persist through summer until autumn frost. Spores are equipped with appendages, that curl or uncurl in response to moisture. This feature aids dispersion and helps spores move deeper into the soil. Common horsetail readily adapts to a wide range of conditions, but prefers full to partial sun, damp to dry conditions, and pH neutral to slightly basic soils. Its aggressive network of rhizomes can penetrate soils to a depth of 6 feet, making it difficult to eradicate once established.  Deep plowing may be necessary to remove rhizomes. This plant is considered toxic for livestock, particularly horses.

The genus name is from Latin equus (horse) and seta (bristle). The species name is from  arvum (ploughed), as this plant readily grows in disturbed soils.  Note that this plant should not be confused with other species in this genus, or with other plants with similar-sounding common names (such as marestail) that is not a member of this genus.

This plant is used horticulturally to make a fungicide for powdery mildew and blights.  It has been used historically in herbal medicines and veterinary uses, and in parts of Asia the buds are eaten as a vegetable.

Insects, Diseases, and Other Plant Problems:  It is considered a weed in many areas where crops are grown.  It may be necessary to perform a deep plowing annually in an attempt to prevent rhizomes from spreading.