The genus name, which means "horsetails", was given by Linnaeus in 1753. 

Montane, subalpine. Streamsides, wetlands. Spring.
Lizard Head Trail, June 19, 2004.

This very common, fern-related ancient plant loves wet areas but is also found in seasonally moist areas.  Pictured at left are the sterile stems that spread from underground roots forming extensive patches.  The sheaths around each node-branching are diagnostic.  The plant feels rough to the touch because of its high silica content.

"Arvense" is Latin for "field".

Montane, subalpine. Streamsides, wetlands. Spring.
Near Forbay Lake Trail, July 12, 2007.

Montane, subalpine. Streamsides, wetlands. Spring.
Shearer Creek Trail, May 17, 2006.

The brown, fertile, unbranched stem bears the reproductive sporangiate cone at its top.  The stem and sporangiate cone grow in the very early spring and wilt in a few days; large patches of branched sterile stems, such as those pictured above, remain through the fall.

Foothills, montane, subalpine. Streamsides, wetlands. Spring.
Lower Scotch Creek Road, June 25, 2000.

This streamside and wetlands loving Equisetaceae has a light and then dark band at each stem joint and the spore producing flower cone is pointed at the tip. 

The high abrasive silica content of the plant makes it useful for scrubbing pots and gave rise to the "Scouring Rush" common name. Backcountry folk use it for cleaning pots. "Horsetails", the second very common name for Hippochaete hyemalis, is derived from the Greek words "Hipp" ("horse") and "chaete" ( "long flowing hair or mane").  "Hyemalis" is Latin for "winter".

Foothills, montane, subalpine. Streamsides, wetlands. Spring.
Calf Creek Falls Trail, Escalante/Grand Staircase National Monument, Utah, October, 23, 2007.

Members of Equisetaceae often occur in dense stands in moist areas.