6. Equisetum arvense Linnaeus, Sp. Pl. 2: 1061. 1753.
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Allostelites arvensis (Linnaeus) Börner; E. arvense f. arcticum (Ruprecht) M. Broun; E. arvense var. arcticum Ruprecht; E. arvense f. boreale (Bongard) Klinge; E. arvense subsp. boreale (Bongard) Á. Löve; E. arvense var. boreale (Bongard) Ruprecht; E. arvense f. campestre (Schultz) Klinge; E. arvense var. campestre (Schultz) Ruprecht; E. arvense f. ramulosum (Ruprecht) Klinge; E. arvense subsp. ramulosum (Ruprecht) W. F. Rapp; E. arvense var. ramulosum Ruprecht; E. boreale Bongard; E. calderi B. Boivin; E. campestre Schultz; E. saxicola Suksdorf.
Plants small to medium-sized. Rhizome ascending, erect, or creeping, blackish brown, nodes and roots with sparse long yellowish brown trichomes or glabrous. Aerial stem annual, dimorphic. Fertile stems appearing in spring earlier than sterile branches, yellowish brown, 5-35 cm tall, 3-5 mm in diam. at middle, not whorled, ridges inconspicuous, with dense grooves, internodes 2-6 cm; sheath castaneous or pale yellow, ca. 0.8 cm, only upper portion of sheath abaxially with a shallow groove; sheath teeth 9-12, castaneous, narrowly deltoid, 4-7 mm. Fertile stems dying back after spores shed (ephemeral). Sterile stems green, up to 40 cm, middle portion of main stem 1.5-3 mm, multiple whorled, below middle portion of main stem branched; internodes 2-3 cm; ridges arc-shaped abaxially, without edges, with cross grains, without tubercles; sheath green, long, narrow; sheath teeth 5 or 6, deltoid, middle portion blackish brown, margin membranous, light brown, persistent. Lateral branches slender, flattened, with 3 or 4 narrow and tall ridges, ridges abaxially with cross grains; sheath teeth 3-5, green, lanceolate, margin membranous, persistent. Strobilus terete, 1.8-4 cm, 0.9-1 cm in diam., apex blunt; stalk prolonged when mature and 3-6 cm. 2n = 216.
Forests, forest margins, under bushes, meadows, banks of rivers and streams, open fields; sea level to 3700 m. Anhui, Chongqing, Fujian, Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Xizang, Yunnan, Zhejiang [W Bhutan, N India, Japan, Korea, Mongolia, Nepal, Russia; C and SW Asia, Europe, North America (including Greenland)].
Morphologically, sterile stems of Equisetum arvense are similar to those of E. palustre, but the former has more abundant and slender and longer lateral branches, which are 3- or 4-ridged and with cross grains abaxially or on ridges.