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   Equisetaceae are the sole survivors of a line of plants going back three hundred million years; members of this family gave rise to many of our coal deposits.  Equisetaceae are circumboreal and are widespread through the United States.  In the semi-deserts, foothills, and mountains of the Four Corners they are common near streams and in wet forests and meadows.

     The various Equisetum are commonly called "Horsetails" or "Scouring Rush".

Equisetum arvense (Field Horsetails)
Equisetaceae (Horsetail Family)

Foothills, 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 branching area are diagnostic.  The plant feels rough to the touch because of its high silica content.

Stems of Equisetum arvense are annual, grow from 10-50 centimeters tall and 1-5 millimeters thick, and are hollow.

Linnaeus named this genus in 1753 from specimens collected in Europe. "Equisetum", is derived from the Latin "equus" for "horse" and "seta" for "bristle".  "Arvense" is Latin for "field".

Equisetum arvense (Field Horsetails)
Equisetaceae (Horsetail Family)

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

     

Equisetum arvense

Equisetum arvense (Field Horsetails)
Equisetaceae (Horsetail Family)

Foothills, montane, subalpine. Streamsides, wetlands. Spring.
Shearer Creek Trail, May 17, 2006 and Ryman Creek Trail, May 29, 2014.

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.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Equisetum arvense