BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Equisetum arvense | Field Horsetail 



GENERAL BOTANICAL CHARACTERISTICS : 
Field horsetail is a native, perennial, rhizomatous cryptogam.  The
sporophyte is dimorphic with unbranched, fertile (stroboliferous),
spore-producing stems and branched, sterile stems.  The spores germinate
to produce a distinct gametophytic generation.  The prothallus
(gametophyte) is tiny, from 0.002 to 0.008 inch (0.5-2.0 mm) in height
(occasionally up to 0.016 inch [4 mm] in the center) and irregularly
lobed or branched [4,14].

The sterile stems are jointed, hollow, usually erect, and bear up to 20
whorls of slender branches [9].  They are usually from 2 to 24 inches
(5-60 cm) tall, rarely to 40 inches (1 m) tall [25].  The inconspicuous,
scalelike leaves occur in whorls at the nodes and are connected at their
bases.  The fertile stems are nonchlorophyllous and generally are from 2
to 12 inches (5-30 cm) tall [19,25].  The strobili are from 0.4 to 1.4
inches (1-3.5 cm) long, peduncled, and blunt.  The epidermis of both
types of stems has regularly arranged, silicified projections [23].

The rhizomes of field horsetail are branched and creeping.  They are
similar to the aerial stems except that they are not hollow [9].
Storage tubers are produced on the rhizomes [19].  The rhizomes extend
to a depth of 40 inches (100 cm) or more; 50 percent of the total
rhizome weight is in the top 10 inches (25 cm) of soil, 23 percent in
the next 9.2 inches (23 cm), and the rest deeper [65].  Successive,
layered horizontal rhizome systems occur at about 12-inch (30 cm)
intervals.  Golub and Wetmore [24] found five such layers by digging to
a 6.6 foot (2 m) depth, noting that the system extended even deeper.
Root development takes place at the bases of lateral branch buds, both
on rhizomes and erect shoots [33].


RAUNKIAER LIFE FORM : 
   Geophyte


REGENERATION PROCESSES : 
The main mode of reproduction of field horsetail is asexual; conditions
for the production of gametophytes from spores are limited and
relatively rare [14,45].

Asexual reproduction:  Field horsetail spreads from extensive rhizomes.
Even short segments of broken rhizomes (1.2 inches [3 cm]) will sprout
[8].  Overwintering buds develop at the nodes of the rhizomes [29].

Sexual reproduction:  The spores of field horsetail are equipped with
elaters, which are long appendages that expand and contract with changes
in humidity.  Elaters function to dig the spore into the soil surface
and to tangle spores together, thereby creating a larger propagule and
increasing the probability that prothalli will be close enough to ensure
fertilization.  Elaters may also aid in wind dissemination.  Spores
released by the strobiliferous stems are dispersed by wind or water.
The spores are thin-walled, short-lived, and quickly germinate under
moist conditions [31].  The spores germinate to form prothalli:  tiny
plants only a few cell layers thick that are usually either male or
female, producing only antheridia or archegonia, respectively.  Swimming
sperm are released by the antheridia and require water for transport to
the egg-containing archegonia.  After fertilization takes place, the
sporophytic generation (the identifiable large plant) develops in situ,
growing out of the prothallus.


SITE CHARACTERISTICS : 
Field horsetail is a facultative wetland species [27].  Field horsetail
occurs in woods, fields, meadows and swamps, and moist soils alongside
streams, rivers, and lakes, and in disturbed areas [9,25].  Field
horsetail usually occurs on moist sites but can also be found on dry and
barren sites such as roadsides, borrow pits, and railway embankments
[9,35].  Under suitably moist climatic conditions, gametophytes occur on
newly deposited mud flats and gravel banks of rivers and lakes [14].

In the Adirondack Mountains of New York, field horsetail occurs from 210
to 2,100 feet (64-640 m) in elevation [42].  In Alaska, field horsetail
is widely distributed from sea level to alpine communities.  On alpine
sites it is found on heaths, moist meadows, and rocky slopes [56].
Field horsetail is found at a wide range of elevations.  Elevational
distributions from selected western states are as follows [13]:

Utah          4,700 to  8,000 feet (1,400-2,400 m)
Colorado      5,100 to 10,800 feet (1,500-3,290 m)
Wyoming       4,900 to  9,700 feet (1,500-3,000 m)
Montana       2,900 to  4,600 feet (  880-1,400 m)


SUCCESSIONAL STATUS : 
Facultative Seral Species

Field horsetail is present in both seral and climax communities; its
presence is largely dictated by edaphic conditions rather than shade or
other factors.  Field horsetail is an early colonizer on floodplain
deposits.  These communities are often destroyed by flooding before
beingcan stabilized by willow establishment [62].  Field horsetail
continues to be present through succession, occurring under more
developed willow-alder communities, as an herbaceous layer dominant with
meadow horsetail (Equisetum pratense) under open balsam poplar (Populus
balsamifera)/thinleaf alder (Alnus tenuifolia) stands, and in the
herbaceous layer of closed balsam poplar/white spruce communities [62].

Field horsetail is an early colonizer of moist, primary successional
sites created by glacial retreat [59].  It is among the most common and
abundant sprouter in areas disturbed by debris from drilling activity in
northern Alaska.  In most of these areas, field horsetail sprouted from
rhizomes already present under the debris [17].  Logging or logging and
burning may either maintain or increase field horsetail cover, depending
on pretreatment levels and forest cover type [12,15].


SEASONAL DEVELOPMENT : 
Strobiliferous shoot buds are initiated in July, August and into
September.  Vegetative buds are initiated in October and November.
Strobiliferous buds elongate early in spring (March to May, depending on
latitude), usually before the vegetative stems elongate [29].  Emergence
is earliest in dry sandy places, later in wet or clay soils [9].  Spores
are shed in early May in the Adirondack Mountains of New York [42].  The
strobiliferous shoots die after the spores are shed [4].  Sterile stems
emerge in May, producing branches after they are 3 to 5 inches (8-12 cm)
in height [9,33].

Stems are killed by hard frost but may live into winter in areas where
they are protected [9].  Gametophytes are killed by frost; they do not
live longer than one growing season [14].

Related categories for Species: Equisetum arvense | Field Horsetail