Wood Horsetail

More info for the term: prescribed fire

Hamilton's Research Papers (Hamilton 2006a, Hamilton 2006b) provide information on prescribed fire and postfire response of many plant species, including wood horsetail, that was not available when this species review was originally written.

More info for the term: woodland

wood horsetail
woodland horsetail
sylvan horsetail

More info for the term: natural

Wood horsetail is included on Virginia's rare and endangered vascular plants list [31]. It is listed as threatened in Ohio by the Natural Heritage Program [47].

More info for the term: gametophyte

Wood horsetail is a perennial, deciduous, homosporous pteridophyte [1,9].  Sterile stems are green with lacy branches and grow up to 28 inches (70 cm) tall.  Fertile stems are at first unbranched and lack chlorophyll but become branched and green after spores are released. Strobili are usually 1 inch (3 cm) long and are borne on short stalks at the apices of fertile stems [5,18,39].  The spores germinate to produce a distinct gametophytic generation.  The unisexual gametophyte is very small, generally from 0.002 to 0.008 inch (0.5-2.0 mm) in height [9]. Wood horsetail often forms large stands [24].  It has extensive creeping rhizomes which may outweigh aerial shoots by a ratio of 100 to 1 [1].

Wood horsetail is a circumboreal species [18,19,21,28].  In North America it is distributed throughout Alaska and Canada south to the Pacific Northwest, the Great Lakes states, New England, and North Carolina [5,14,33,36].

More info for the terms: fire regime, herb, phenotypic plasticity, rhizome, succession

Wood horsetail survives repeated fires by means of deeply buried rhizomes that are apparently almost indestructible [1].  The extensive rhizome system penetrates well into mineral soil or clay, allowing revegetation even after severe fire [1,12,45].  Wood horsetail may be the most abundant herb species after fires in black spruce stands in Alaska.  It sprouts after fire in any stage of succession [45]. Wood horsetail also colonizes recently burned areas by wind-dispersed spores [23].  Its phenotypic plasticity enables it to survive the environmental changes associated with postfire succession [1]. FIRE REGIMES: Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".

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More info for the term: geophyte

      Geophyte

More info for the term: forest

Wood horsetail most commonly occurs in cool, moist, shaded to somewhat open forests [5,18,21,39].  It also occurs on streambanks, and in bogs, swamps, and forest openings [5,25,30,33].  Wood horsetail is an indicator of boreal and cool-temperate climates, and very moist to wet, nitrogen-poor soils [25].  Soils may be poorly drained to moderately well drained [6,27].  Wood horsetail is found from lowlands to subalpine regions [22].  In the Adirondack Mountains of New York, it occurs from 1,460 to 2,200 feet (438-660 m) in elevation [27].  Gametophytes of wood horsetail are found on substrates with a lower pH than are gametophytes of other horesetail species [10].

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

     1  Jack pine
     5  Balsam fir
    12  Black spruce
    13  Black spruce - tamarack
    15  Red pine
    16  Aspen
    17  Pin cherry
    18  Paper birch
    20  White pine - northern red oak - red maple
    21  Eastern white pine
    22  White pine - hemlock
    23  Eastern hemlock
    24  Hemlock - yellow birch
    25  Sugar maple - beech - yellow birch
    26  Sugar maple - basswood
    27  Sugar maple
    28  Black cherry - maple
    30  Red spruce - yellow birch
    31  Red spruce - sugar maple - beech
    32  Red spruce
    33  Red spruce - balsam fir
    35  Paper birch - red spruce - balsam fir
    37  Northern white-cedar
    38  Tamarack
    39  Black ash - American elm - red maple
    60  Beech - sugar maple
    63  Cottonwood
   107  White spruce
   108  Red maple
   201  White spruce
   202  White spruce - paper birch
   203  Balsam poplar
   204  Black spruce
   205  Mountain hemlock
   206  Engelmann spruce - subalpine fir
   210  Interior Douglas-fir
   212  Western larch
   213  Grand fir
   215  Western white pine
   217  Aspen
   218  Lodgepole pine
   221  Red alder
   222  Black cottonwood - willow
   223  Sitka spruce
   224  Western hemlock
   225  Western hemlock - Sitka spruce
   226  Coastal true fir - hemlock
   227  Western redcedar - western hemlock
   228  Western redcedar
   229  Pacific Douglas-fir
   230  Douglas-fir - western hemlock
   235  Cottonwood - willow
   251  White spruce - aspen
   252  Paper birch
   253  Black spruce - white spruce
   254  Black spruce -  paper birch

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

   FRES10  White - red - jack pine
   FRES11  Spruce - fir
   FRES17  Elm - ash - cottonwood
   FRES18  Maple - beech - birch
   FRES19  Aspen - birch
   FRES20  Douglas-fir
   FRES22  Western white pine
   FRES23  Fir - spruce
   FRES24  Hemlock - Sitka spruce
   FRES25  Larch
   FRES26  Lodgepole pine
   FRES28  Western hardwoods
   FRES37  Mountain meadows

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the terms: bog, forest

   K001  Spruce - cedar - hemlock forest
   K002  Cedar - hemlock - Douglas-fir forest
   K003  Silver fir - Douglas-fir forest
   K004  Fir - hemlock forest
   K008  Lodgepole pine - subalpine forest
   K012  Douglas-fir forest
   K013  Cedar - hemlock - pine forest
   K014  Grand fir - Douglas-fir forest
   K015  Western spruce - fir forest
   K025  Alder - ash forest
   K093  Great Lakes spruce - fir forest
   K094  Conifer bog
   K095  Great Lakes pine forest
   K096  Northeastern spruce - fir forest
   K097  Southeastern spruce - fir forest
   K098  Northern floodplain forest
   K099  Maple - basswood forest
   K101  Elm - ash forest
   K102  Beech - maple forest
   K103  Mixed mesophytic forest
   K106  Northern hardwoods
   K107  Northern hardwoods - fir forest
   K108  Northern hardwoods - spruce forest

Aboveground stems of wood horsetail are killed by fire [1].  Rhizomes are resistant to fire because they are buried deep in mineral soil [12,45].

In interior Alaska, horsetails (Equisetum spp.) comprise the largest component of the spring diet of black bears.  Horsetails and blueberries (Vaccinium spp.) are the two most important plant genera to black bears in the region [20].

More info for the terms: bog, forest, herbaceous, taiga

Wood horsetail is most prevalent in lowland wet conifer forests but is
also common in mixed upland, dry conifer, and deciduous forest habitats
[3].  In addition, it is found in meadows, bogs, swamps, and along
streambanks [5,19,34,46].

The following publications classify wood horsetail as a dominant
herbaceous layer component:

Field guide to forest ecosystems of west-central Alberta [6]
Classification, description, and dynamics of plant communities after
  fire in the taiga of interior Alaska [15]
The Alaska vegetation classification [44]

Species commonly associated with wood horsetail in jack pine (Pinus
banksiana), white spruce (Picea glauca), or black spruce (P. mariana)
habitats include alder (Alnus spp.), willows (Salix spp.), highbush
cranberry (Viburnum edule), bunchberry (Cornus canadensis), bog Labrador
tea (Ledum groenlandicum), twinflower (Linnaea borealis), blueberry
(Vaccinium spp.), red raspberry (Rubus idaeus), gooseberry (Ribes spp.),
honeysuckle (Lonicera involucrata), leatherleaf (Chamaedaphne
calyculata), prickly rose (Rosa acicularis), wild lily-of-the-valley
(Maianthemum canadense), naked miterwort (Mitella nuda), coltsfoot
(Petasites spp.), common yarrow (Achillea millefolium), fireweed
(Epilobium angustifolium), bluejoint reedgrass (Calamagrostis
canadensis), sedges (Carex spp.), fire moss (Ceratodon purpurea),
feathermosses (Hylocomium splendens, Pleurozium schreberi), and sphagnum
mosses (Sphagnum spp.) [1,4,6,11,29].

More info for the terms: fern, fern ally

Fern or Fern Ally

Wood horsetail is poisonous to humans [8].

Dry matter nutrient content values of wood horsetail collected in the
Wallace-Aikens Lake area, Manitoba, were:  6.7 percent crude protein,
1.36 percent calcium, and 0.09 percent phosphorus.  Dry matter
digestibility was 27.9 percent [35].

     AK  CT  DE  ID  IL  IN  IA  KY  ME  MD
     MA  MI  MN  MT  NH  NJ  NY  NC  ND  OH
     OR  PA  RI  SD  TN  VT  VA  WA  WV  WI
     WY  AB  BC  MB  NB  NF  NT  NS  ON  PE
     PQ  SK  YT

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In the Northern Clay Belt Region, Ontario, fertile shoots of wood horsetail appear before sterile shoots, liberate their spores, and die before sterile shoots complete their growth.  Most fertile shoots die by the end of June, and sterile shoots begin to die in August [1].  In most areas within its distributional range, wood horsetail spores are shed from April through May [5,9,18].

More info for the terms: cover, frequency, mesic, succession

In the Northern Clay Belt Region of Ontario, wood horsetail recovers rapidly after fire and is one of the most prominent postfire species. It becomes less abundant in the later stages of postfire succession, but is still present under mature spruce (Picea spp.) stands up to 240 years old.  Shoots that appear immediately after fire are sterile, but up to 20 percent of the stems that appear in postfire year 1 are fertile [1]. In central Saskatchewan, wood horsetail was present 4 years after fires on moist and moderately moist sites in jack pine clearcuts [4]. Wood horsetail regenerates rapidly following fire in black spruce/feathermoss forests in southeastern Newfoundland, and its abundance may exceed prefire levels.  Its frequency was 27.8 percent in unburned areas and 21.1 percent in areas that had been burned 5 years previously [16]. On mesic black spruce sites in interior Alaska, wood horsetail is present throughout all stages of postfire succession.  The following cover and frequency percentages were reported [15]: Stage        Years since fireCover  Frequency __________________________________________________________________________ Newly burned        0-1       less than 0.5      10.0 Moss-herb           1-5       4.0      65.0 Tall shrub-sapling  5-30      2.0      13.0 Dense Tree         30-55      less than 0.5      11.0 Mixed hardwood-spruce     56-90      less than 0.5       5.0 Spruce             90-200+    4.0      49.0 After the 1971 Wickersham Dome Fire near Fairbanks Alaska, wood horsetail had the following cover and frequency percentages in lightly burned and severely burned black spruce stands (control plot cover and frequency was 1.25 and 60.0 percent, respectively) [43]:         1971     1972      1973     1974     Light  Severe   Light   Severe   Light  Severe   Light   Severe ___________________________________________________________________________ Cover0.1     02.65     3.35    2.6    3.65.7     8.95 Frequency  10.0     0      95.0     80.0    95.0   80.0      85.0    90.0 In this same study area, wood horsetail had cover values on fireline sites of 4, 40, and 12 percent in 1972, 1975, and 1980, respectively [42].

More info for the terms: geophyte, ground residual colonizer, herb, rhizome

   Rhizomatous herb, rhizome in soil    Geophyte, growing points deep in soil    Ground residual colonizer (on-site, initial community)    Initial-offsite colonizer (off-site, initial community)

More info for the term: rhizome

Wood horsetail primarily reproduces by vegetative means; the majority of shoots arise from rhizomes [1,12].  Rhizome systems are extensive, deeply buried, and extremely long-lived (perhaps several thousand years old) [1]. The establishment of gametophytes and subsequent sexual reproduction is rare in the wild due to an extremely narrow habitat tolerance.  The most critical factor for sexual reproduction appears to be the initial establishment of spores.  Gametophytes only establish on recently exposed bare mud, such as around resevoirs or streambanks following flooding.  Wood horsetail has a very limited spore dispersal period, and spores are short-lived.  Male gametophytes grow at a much slower rate than females.  There is also evidence of early male mortality. Gametophytes reach sexual maturity at 3 to 5 weeks and then produce a constant supply of gametes until death.  The sex ratio of a population is determined by environmental conditions; female gametophytes are more likely to be produced under favorable conditions [9].  The frequent occurence of Equisetum hybrids suggests, however, that sexual reproduction is a common occurrence in this genus [10].

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

    1  Northern Pacific Border
    2  Cascade Mountains
    8  Northern Rocky Mountains
    9  Middle Rocky Mountains
   15  Black Hills Uplift

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More info for the terms: climax, succession

Facultative Seral Species Wood horsetail is shade tolerant [25]. It is found throughout all successional stages to climax forests [45].  Wood horsetail colonizes newly exposed mud on streambanks and floodplains [9], and it invades recently burned areas [25].  In floodplain succession in interior Alaska, wood horsetail is common in 200-year-old white spruce-black spruce and climax black spruce/sphagnum forests [41].  It is also widespread in black spruce stands from 26 to 120 years old in Ontario [38].  Wood horsetail is common in stable, mature forests in west-central Alberta [6].

More info for the term: fern

The currently accepted scientific name of wood horsetail is Equisetum
sylvaticum L. [5,14,22,33]. The following varieties and form are
recognized [7,14,33,36]:

Equisetum sylvaticum var. sylvaticum -- with scabrous branches
E. sylvaticum var. pauciramosum Milde. -- smooth branches, slightly branched
E. sylvaticum f. multiramosum Fern. -- smooth branches, copiously branched

Wood horsetail is a highly variable species; many varieties and forms
have been described that have little taxonomic significance [5].

Wood horsetail apparently hybridizes with meadow horsetail (E. pratense)
[10].