Washington Flora Checklist
A Checklist of the Vascular Plants of Washington State
Hosted by the University of Washington Herbarium


Checklist » Equisetaceae
Equisetaceae   (Horsetail Family)

Notes: FNA2: "Equisetum occurs in moist places such as riverbanks, lakeshores, roadsides, ditches, seepage areas, meadows, marshes, and wet woodlands. Aerial stems of Equisetum vary considerably in habit and appearance, even on individual plants, because of environmentally induced modifications affecting height and branching. Many taxonomically trivial varieties and forms have been named. For an extended discussion of this, see R.L. Hauke (1966). Four widespread, named hybrids are treated in the key and fully described below.

In species descriptions and in the key, length and width are given for the leaf sheath, excluding the free teeth. If the length and width of flattened sheaths are approximately equal and the sides are straight, the sheath is more or less square in face view, i.e., about as long as broad; if the length is greater than the width and the sides are straight, the sheath is more or less elongate in face view, i.e., longer than broad; if the length is greater than the width and the sides are slightly convex, the sheath is elliptic in face view. Stomates are usually visible at 20× magnification.

Reticulation in Equisetum is summarized in the reticulograms, which show the known and expected hybrids in North America. Most of those in Equisetum subg. Equisetum are still unknown in North America, but they should be sought, especially north of 45° N latitude. According to W.J. Cody and D.M. Britton (1989), E . × font-queri occurs rarely in British Columbia and materials possibly representing E . × arcticum Rothmaler have been taken in the Richardson Mountain region of Mackenzie. R.L. Hauke (1978) cited collections of E . × font-queri from British Columbia and California."

Family Synonyms: (none)

» Hauke, R.L. 1966. A systematic study of Equisetum arvense. Nova Hedwigia 13: 81--109. Hauke, R.L. 1979. Equisetum ramosissimum in North America. Amer. Fern J. 69: 1--5.

Family treatment authored by Peter F. Zika; last updated 12/22/2008 by David Giblin
Taxon (native species in boldface) # Synonyms Common Names
Equisetum arvense L.   [FNA2, H&C] 1 common or field horsetail
Equisetum ×ferrissii Clute   [FNA2, H&C] 1 Ferriss' scouring rush
Equisetum fluviatile L.   [FNA2, H&C] 1 swamp, water, or river horsetail
Equisetum hyemale L. ssp. affine (Engelm.) Calder & Roy Taylor   [FNA2] 5 common scouring rush, Dutch rush, prairie scouring rush
Equisetum laevigatum A. Braun   [FNA2, H&C] 2 smooth scouring rush
Equisetum ×litorale Kühlew. ex Rupr.   [FNA2] 0 shore horsetail
Equisetum ×mackaii (Newman) Brichan   [FNA2] 2 small scouring rush
Equisetum ×nelsonii (A.A. Eaton) J.H. Schaffner (E . laevigatum x E . variegatum)   [FNA2] 0 Nelson's horsetail
Equisetum palustre L.   [FNA2, H&C] 1 marsh horsetail
Equisetum scirpoides Michx.   [FNA2, H&C] 0 dwarf scouring rush, sedgelike horsetail
Equisetum sylvaticum L.   [FNA2, H&C] 0 wood or woodland horsetail
Equisetum telmateia Ehrh. ssp. braunii (J. Milde) Hauke   [FNA2] 2 giant or great horsetail
Equisetum variegatum Schleich. ex F. Weber & D. Mohr ssp. alaskanum (A.A. Eaton) Hultén   [FNA2] 1 Alaskan scouring rush
Equisetum variegatum Schleich. ex F. Weber & D. Mohr ssp. variegatum    [FNA2] 1 northern scouring rush, variegated horsetail

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