BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Equisetum sylvaticum | Wood Horsetail 



GENERAL BOTANICAL CHARACTERISTICS : 
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].


RAUNKIAER LIFE FORM : 
   Geophyte


REGENERATION PROCESSES : 
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].


SITE CHARACTERISTICS : 
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].


SUCCESSIONAL STATUS : 
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].


SEASONAL DEVELOPMENT : 
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].

Related categories for Species: Equisetum sylvaticum | Wood Horsetail