Erect plants arising from a black perennial branching rhizome. Stems hollow except at nodes, with sheaths at nodes. Sheaths represent whorls of fused leaves. Fertile stems terminate in a cone which bears sporangia. It is advisable to identify these plants from fresh material since artifacts are sometimes produced which would provide misleading results in keying. For example, the collar or sheath which is tight around the stem in fresh material of some species may not shrink as much as the stem in drying, and thus appears flared, a characteristic of a different species.

Indians of central California used Equisetum to polish their arrows, according to Kroeber. The abrasive quality of the stems due to silicates in the cell walls was well known by early white settlers in the west who used them to clean household utensils, hence the name “scouring rush” applied to some species by the pioneers. This abrasive is also said to cause death in sheep and cattle as a result of internal hemorrhage. A number of species of Equisetum have been used medicinally as herbs. They contain aconitic acid and are used as diuretics.

KEY TO THE SPECIES:

Two kinds of stalks: sterile with whorls of branches, and unbranched

fertile ones with terminal cone E. arrense

Only one kind of stalk, eventually bearing cones

Cones pointed at apex
Sheath at nodes closely pressed to stem, stems rough to touch E. hiemale
Sheath flared at nodes, stems smooth to touch E. laevigatum
Cones rounded at apex E. kansanum

COMMON HORSETAIL

Equisetum arvense L. (Fig. 49, 50)

Sterile stems 1/2 to 2 feet high, slender, 10-15 furrows, nodal sheath loose, ending in about 12 brown teeth. Whorls of branches numerous, jointed as in the stems with only 4 teeth on each sheath. Fertile stems 4 to 7 inches high having 3 to 5 nodes with long, loose sheaths, often brown, and a terminal spore-producing cone 1 to 1 1/2 inches long. Fertile stems appear very early in the spring and are rarely seen because after a few days they shed their

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Fig. 49 COMMON HORSETAIL (Equisetum arvense). Upper: Growing on a sandy stream bank. Sterile branches only. Lower: COMMON SCOURING RUSH (Equisetum hiemale). Growing as a dense stand in both open sunlight and in shade.

spores and die down. The sterile stalks remain for the whole season.

Common in sandy wet soil in or near streams or swamps 2,000 to 9,000 feet elevation in the Sierra Nevada. Also known from the arctic, Europe, Asia, and northern Africa.

COMMON SCOURING RUSH

Equisetum hiemale L. var. californicum Milde. (Fig. 49, 51)

Stout evergreen stems 2 to 4 feet high, rough to touch, simple or rarely branched, branches usually bearing cones. Whorls of sterile branches not present at the nodes. Long brown teeth on the sheath at the nodes are deciduous early in the season, leaving a smooth rim to the sheath. The sheath nearly or quite as broad as long, close to the stein, never flared from it. Color characteristics of the sheaths variable in the species, but basically gray in color. In younger stems one upper black ring present; in older stems an upper and a lower black ring usually visible. The ovate cones are 1/2 to 1 1/2 inches long, yellow or black, pointed at apex.

Also known as the Western Scouring Rush and the Rough Scouring Rush. The rhizomes may extend a great distance underground. One rhizome, which the author traced, extended 6 feet from the nearest vertical stern on the same plant. This species grows in the Coast Range and Sierra Nevada from 2,000 to 5,000 feet elevation along sandy stream banks sometimes in very dense stands. Known in Alaska, Utah and California.

SMOOTH SCOURING RUSH

Equisetum laevigatum A. Br. (Fig. 51)

Similar in general appearance to E. hiemale, but the sterns here usually smaller, always smooth to touch. Evergreen stems 1 to 2 feet high,

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Fig. 50 COMMON HORSETAIL (Equisetum arvense). Left: A sterile branched stalk, the one most commonly observed. Right: Fertile stalk with its terminal cone and loose sheath-like collar a nodes.

Fig. 51 COMMON SCOURING RUSH (Equisetum hiemale). SMOOTH SCOURING RUSH (Equisetum laevigatum)

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Fig. 51 COMMON SCOURING RUSH (Equisetum hiemale). Left: Base including one upright stem and a portion of the long rhizome. Solid black portions grow underground. Center: Top of some plant including cones and branches. Right: SMOOTH SCOURING RUSH (Equisetum laevigatum). Fertile branch with pointed cone and flared sheaths at nodes.

usually unbranched, pale green. Sheath longer than broad, flaring open, teeth of the sheath deciduous, resulting in a smooth border to the sheath when they fall. Cones 1/2 to 1 inch long borne at the ends of the stems.

Sometimes called Braun’s Scouring Rush. This species is found in the Sierra Nevada at such places as Granite Creek and Round Meadow in Sequoia National Park, along the Merced River in Yosemite Valley and northward to British Columbia, eastward to the Great Lakes, Massachusetts, Virginia and Georgia, southward to Mexico and Guatemala.

KANSAS SCOURING RUSH

Equisetum kansanum Schaffner (Fig. 52)

Similar in appearance to E. laevigatum because the sheath flares open. This species is not evergreen and the cone is rounded at its tip.

Also known as the Kansas Horsetail. Least common of the species found in the Sierra, it has been collected by Carl Sharsmith near Arch Rock, Yosemite. It is reported from Howells, Sequoia National Park and is known in a few widely scattered areas from Ohio westward to British Columbia and in Texas.