Switchgrass

More info for the terms: cover, litter, warm-season, wildfire

Switchgrass may increase modestly following late spring burning if
moisture conditions following the fire are favorable, but it does not
exhibit as dramatic an increase as other warm-season grasses such as big
or little bluestem. Knapp [41] attributes this to switchgrass's growth
form. It has a high ratio of reproductive to vegetative shoots and is
therefore much less leafy than big bluestem. Furthermore, switchgrass
litter does not matt down, and sunlight reaches emerging shoots even in
unburned stands. In comparison, little sunlight reaches shoots in
unburned big bluestem stands. Thus big bluestem often increases
dramatically with the favorable conditions of increased solar radiation
and warmer soil temperatures following burning, while preburn and
postburn environments in switchgrass stands are not as different.

Morrison and others [53] felt that fires in the Nebraska Sandhills may
affect the vegetation differently than fires in other grasslands because
the sandy soils become droughty late in the growing season, and thus
increases in grass cover do no occur. On uplands of the Sandhills, they
found that switchgrass cover 1 year after an October wildfire was
slightly lower on burned areas than unburned areas.

switchgrass
prairie switchgrass
tall panic grass

More info for the terms: cover, density, warm-season

Switchgrass's tall, vigorous, erect growth form which remains standing
throughout the winter, provides excellent protective and concealment
cover for upland game birds and ducks. These birds use switchgrass
cover for loafing, night roosting, escape from predators, protection
from blizzards, and nesting [65]. When compared with a number of
warm-season grasses and alfalfa (Medicago sativa) in Iowa, ring-necked
pheasant nest density and hatch success were highest in switchgrass
stands [30]. Other birds which successfully nested in switchgrass in
Iowa included the northern bobwhite, mourning dove, and several
passerine species [29]. On the Sheyenne National Grasslands, North
Dakota, switchgrass-dominated sites are preferred nesting areas of the
greater prairie-chicken and sharp-tailed grouse [51].

Switchgrass can be planted to provide wildlife cover; however, large,
continuous monotypes are not recommended. The maximum size of a planted
stand should be about 40 acres (16 ha) [65]. In western Minnesota and
the eastern Dakotas, switchgrass is recommended for planting along pond
margins to provide duck nesting cover on areas where native vegetation
has been destroyed by farming [21].

More info for the term: warm-season

Switchgrass is a native, erect, coarse, warm-season perennial grass.
Foliage height of mature plants is mostly between 3 and 5 feet (0.9-1.5
m),; the inflorescence, a 6- to 18-inch-long (15-46 cm) open panicle,
often extends to a height of 5 to 7 feet (1.5-2.1 m) [76,77].
Switchgrass has both sodand bunch-forming ecotypes. Bunch-forming
ecotypes are generally encountered on uplands, while sod-forming
ecotypes occur on lowlands [61,75]. Rhizomes of sod-forming switchgrass
on a floodplain in Iowa were 0.12 to 0.27 inch (3-7 mm) thick, 1 to 2
feet (0.3-0.6 m) long, and mostly 2 to 5 inches (5-12 cm) below the soil
surface [77]. In the Southeast, bunch-forming ecotypes have only short,
vertically oriented rhizomes averaging 0.5 inch (1.4 cm) in length,
while sod-forming ecotypes have both short, vertically-oriented rhizomes
and long horizontally-oriented rhizomes (2 to 4 times longer than
vertical rhizomes) [7]. Switchgrass growing on Valentine fine sand in
the Nebraska Sandhills is similar to sod-forming ecotypes of the
Southeast in that plants develop from both vertically and horizontally
oriented rhizomes [10]. Switchgrass roots may reach depths of 10 feet
(3 m) or more [75].

In North America, switchgrass grows south of latitude 55 °N, from
Saskatchewan to Nova Scotia, and south throughout most of the United
States east of the Rocky Mountains. It is most abundant in the Great
Plains and eastern states [15,72].

More info for the terms: density, fire regime, grassland, tiller

During grassland fires, the fire front passes quickly and temperatures 1
inch (2.5 cm) below the soil surface rise very little [42]. Because the
rhizomes of sod-forming switchgrass ecotypes typically occur at depths
of 2 to 5 inches (5-12 cm) [77], they are unharmed by the heat of fire.
Plants burned during the spring when dormant send up vigorous new growth
from these surviving rhizomes. Rhizomes survive summer fires also, but
postfire tiller density may be reduced because of low carbohydrate
reserves and damage to aboveground apical meristems [see Fire Effects On
Plant].

Some bunch-forming switchgrass ecotypes are not well adapted for fire
survival [see Fire Effects On Plant].

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".

More info for the terms: codominant, cool-season, prescribed fire, warm-season

Switchgrass needs periodic fire to maintain its vigor and abundance. On
the Konza Prairie in Kansas, it showed a linear decrease in abundance
with time since burning. On areas burned annually in the spring, it was
a codominant with big bluestem, little bluestem, and indiangrass [32].

In prairie plantings and in newly seeded stands, prescribed late spring
burning can be used to maintain or increase switchgrass biomass and
control undesirable cool-season grasses. Cool-season grasses are harmed
by this treatment, because they begin growth early in the spring, and
are actively growing at the time of burning. Conversely, warm-season
grasses begin growth in late spring, and are thus dormant at the time of
burning. Switchgrass was the dominant warm-season grass on a 6-year-old
prairie planting in Wisconsin. In late August following a prescribed
fire on May 15, warm-season grass biomass on the Wisconsin planting
increased 10 percent, while cool-season grass biomass decreased 81
percent [19]. Summer fires, however, favor cool-season grasses. For
example, in north-central South Dakota, switchgrass and big bluestem
dominated lowlands burned in late April, while cool-season grasses
(Agropyron, Poa, Stipa) dominated lowlands burned in August [66].

In central North Dakota, Duebbert and others [21] recommend burning
warm-season grasses between May 15 and June 15. Prescribed burning
guidelines have been outlined for the Northern Great Plains [80].

More info on this topic.

Cryptophyte

More info for the terms: fresh, mesic

Switchgrass is a mesic grass that grows on a wide variety of soil
textures if soil moisture is adequate [74]. Studying its distribution
along a water gradient in Kansas, Knapp [40] found that switchgrass
favored mesic sites, and concomitant physiological studies showed it was
less able to adjust osmotically to drought than big or little bluestem.
In the tallgrass prairie region, switchgrass is generally most abundant
on low-lying areas that receive some upslope moisture [77]. It is
seldom found on dry uplands of the West [67] but does grow on
upper-elevation sand dunes in the Nebraska Sandhills. Deep-rooted
switchgrass grows well on the sand dunes because even small amounts of
precipitation penetrate the coarse sand and thus subsurface moisture is
available throughout the growing season [6].

Besides mesic prairies, switchgrass also commonly grows in fresh and
brackish marshes, on dunes and along lakeshores, and in oak and pine
savannas. Switchgrass is tolerant of spring flooding but not of high
water tables [74]. It is tolerant of moderate soil salinity and
acidity. It grows in soils ranging in pH from about 4.5 to 7.6 [72,74].

More info for the terms: density, fire intensity, fuel, litter, meristem, rhizome, tiller

Fire removes aboveground parts of switchgrass. Switchgrass litter is
resistant to matting down. This standing dead material is apparently a
good fuel source which readily carries fire.

Most switchgrass plants survive fire because of protected underground
rhizomes, but the vigor and extent of postfire tiller growth is
dependent upon season of burning, fire intensity, and plant growth form
(sod- or bunch-forming ecotype). If burned when dormant, switchgrass is
not harmed by fire and, drawing upon stored carbohydrate reserves,
resumes growth in the spring as usual. Regrowth following summer
burning, however, is hampered because (1) switchgrass's apical meristems
are elevated above the soil surface at this time and can be consumed by
fire and (2) carbohydrate reserves for initiation of new growth are low
at this time of year. If the apical meristem is destroyed by fire, new
growth must come from the initiation of new tillers from crown or
rhizome buds [64]. In Nebraska, switchgrass meristems protrude above
the soil surface beginning in mid-June, and extend more than 1 inch (2.5
cm) above the soil surface by late June [9,33].

During summer grass fires, fire intensity is dependent upon fuel
quantity. Where fuel loads are heavy, grass fires can be relatively
intense, resulting in the consumption of switchgrass's aboveground
meristems. Conversely, under light fuel loads, meristems may survive.
For example, during summer prescribed fires in Oklahoma tallgrass
prairie (Andropogon-Sorgastrum-Panicum), fire intensity at the soil
surface (measured by fire temperature and duration) was four times as
high on ungrazed plots (fuel load = 1,031 grams/meter square) than on
grazed plots (fuel load = 443 grams/meter square). Postfire recovery on
grazed plots was quicker, with regrowth coming mostly from tillers free
of apical meristem damage. On ungrazed plots, new growth came from
newly initiated tillers from rhizomes, but was not vigorous, and 2
months after the fire tiller density remained well below preburn levels
[25].

Both sod- and bunch-forming switchgrass ecotypes were burned annually in
January in Georgia [7]. No sod-forming types were harmed by fire, but
numerous bunch type clones were killed. Bunch types often had the
center of the bunch elevated above the soil surface, leaving the roots
and rhizomes exposed.

More info for the terms: cool-season, cover, warm-season

Switchgrass is an important livestock forage. In managed stands, it is
used primarily for warm-season pasture and hay. Its use as warm-season
pasture for cattle has increased in recent years in the Corn Belt. In
this region, 60 to 70 percent of its growth occurs after June 1,
compared with cool-season grasses which make over 60 percent of their
growth before June 1. Thus cattle weight gains are high when both
pasture types are used in a rotational grazing system [28]. In the
Southeast, switchgrass is primarily used for cattle pasture, and less
often cut for hay [48]. Because it is somewhat shade-tolerant, it is an
important forage of thinned-pinelands in the Southeast [34].

Switchgrass hay yields are high. Two to four tons per acre (4.5-9 t/ha)
are not uncommon [14,48,72].

Switchgrass is generally unimportant in the diets of wild ungulates in
the West [20,45,46]. In the Southeast, white-tailed deer paw up and eat
the rhizomes when winter food is scarce [34].

For ducks, upland game birds, songbirds, and small mammals, switchgrass
provides excellent cover and the seeds are an important food source
[56,68].

More info for the terms: climax, codominant, grassland, mesic, xeric

Switchgrass is a codominant of climax tallgrass prairie, which once
stretched from eastern North Dakota and Minnesota to Oklahoma. Kuchler
[43] designated this as Bluestem Prairie (Andropogon-Panicum-Sorghastrum).
The key dominants are big bluestem (Andropogon gerardii var. gerardii), little
bluestem (Schizachyrium scoparium), switchgrass, and indiangrass (Sorghastrum
nutans). Within this region, switchgrass is common over a variety of sites
but is generally considered a mesic grass and is most abundant on lowlands.
Along with Canada wildrye (Elymus canadensis), it may codominate lowlands
situated between more xeric big bluestem-dominated communities and more mesic
stands of prairie cordgrass (Spartina pectinata) [75,76].


In coastal and blackland prairies of Texas, switchgrass may codominate poorly
drained lowlands with eastern grama grass (Tripsacum dactyloides), tall dropseed
(Sporobolus asper var. asper), and/or indiangrass [12,17,18].

Publications describing grassland communities dominated by switchgrass
are listed below:

• Plant communities of the blackland prairies of Texas [12]
• Remnant grassland vegetation and ecological affinities of upper coastal prairie of Texas [17]
• North American Prairie [75]

More info for the term: graminoid

Graminoid

More info for the term: warm-season

Because of early elevation of shoot apical meristems and a high ratio of
reproductive to vegetative culms, switchgrass is relatively intolerant
of grazing and is a decreaser [9,74]. Of numerous warm-season grasses
studied in Oklahoma, swithcgrass was the most susceptible to damage from
clipping [61]. Switchgrass is tolerant of winter grazing but is
unpalatable at that time [67].

Switchgrass in early growth stages is nutritious. After seedheads
emerge, however, nutritive value declines rapidly, and the plant
provides only the minimum maintenance energy needs of ruminants [35].
For example, crude protein and in vitro dry matter digestibility (IVDMD)
of Kansas and Nebraska switchgrass strains grown in Nebraska averaged
17.5 and 68.6 percent in early June, 11.4 and 59.8 percent in late June;
and 8.4 and 51.0 percent in mid-July, respectively [55]. In
Pennsylvania, leaf crude protein and IVDMD of the the switchgrass
cultivar 'Blackwell' was 10.2 and 66.1 percent in late June; 8.9 and
60.7 in mid-July; and 8.3 and 57.7 in early August, respectively [35].
On the Texas High Plains, switchgrass crude protein content was highest
shortly after spring growth began in May, averaging 18.4 percent, but
dropped to under 8.9 percent beginning in June [71].

To provide the optimum combination of forage production and nutritional
quality, switchgrass hay should be harvested about the time the panicles
are beginning to emerge from the boot [72]. Switchgrass hay harvested
at this time averages 50 to 60 percent in vitro dry matter digestibility
(IVDMD) and 8 to 10 percent crude protein [72].

In Nebraska, crude protein content of switchgrass is higher than that of
sand bluestem (Andropogon gerardii var. paucipilus) and big bluestem
[54].

Switchgrass is palatable to cattle, horses, and sheep during the spring
and early summer before the leaves become coarse and tough. By
midsummer, when the seedheads begin to mature, nutrient content and
palatability decline rapidly; by late summer palatability is low
[14,67].

More info on this topic.

More info for the term: warm-season

The stimulus for switchgrass to resume growth in the spring is warming
soil temperatures [52]. Thus the beginning of spring growth for a given
location may vary by a week or two from year to year. In the Great
Plains, new shoots emerge in mid- to late spring about 1 week later than
associated warm-season grasses little bluestem, big bluestem,
indiangrass, and sideoats grama (Bouteloua curtipendula) [2,52,59].
Initiation of spring vegetative growth by location is as follows:

Georgia - March [7]
central Oklahoma - early to mid-April [2,59]
eastern Nebraska - mid to late April [52]
west-central Kansas - late April [3]

Vegetative growth is rapid after the initial spring flush. In the
Missouri River Valley of eastern Nebraska and western Iowa, switchgrass
regrowth resumes in April, and by early June the foliage often exceeds
18 inches (46 cm) in height [76]. The peak of flowering generally
occurs in July in Colorado, Wyoming, Montana, North Dakota, South
Dakota, Minnesota, and Nebraska [50,52]. In Kansas, Missouri, and
Oklahoma flowering primarily occurs in August [52,59]. Risser and
others [61] stated that in the True Prairie, switchgrass seeds are shed
in late fall or winter. However, a phenological study in southeastern
North Dakota found that most switchgrass seeds were shed by mid-August,
only 1 month after flowering occurred [50].

More info for the terms: cover, density, herbaceous, prescribed fire

Switchgrass cover and biomass often increase slightly to moderately
following dormant-season burns. It generally responds best to burning
in late spring, just prior to the start of new growth. For example, in
moderately grazed pastures that were annually burned over a 16-year
period in the Flint Hills of Kansas, switchgrass cover was higher under
late spring burning (May 1) than under early spring (March 20),
midspring (April 10), or no burning [4,47]. Prescribed early and
mid-May burning in North Dakota increased switchgrass canopy coverage,
but late June burning did not. First and second year increases were as
follows [57]:

Switchgrass Canopy Coverage (%)

June 1973 August 1973 June 1974 August 1974

burned May 8, 1973 1.2 2.7 0.6 1.9
control 0.7 0.4 0.15 1.2

burned May 14, 1973 2.8 5.85 1.55 5.1
control 2.1 3.5 0.65 2.7

Numerous other studies have documented increases in switchgrass biomass,
density or cover in the first postfire growing season following dormant
season burns [16,39,60,62,66].

Seedstalk production may increase dramatically following burning.
Following mid-May burning in North Dakota, switchgrass seedstalk density
on burned plots was more than double that of unburned plots (25.2 vs
10.4/meter square) during the first postfire year [57]. A nearly
identical flowering response occurred in central Iowa following a
mid-April prescribed fire, where the number of switchgrass
inflorescences was more than double on burned versus unburned plots
[60]. In eastern Kansas, a 5-year-old planted switchgrass stand burned
in late April yielded 250 pounds of seeds per acre (280 kg/ha), while an
unburned portion of the same stand yielded only 190 pounds of seeds per
acre (212 kg/ha) [13].

The Research Project Summary, Herbaceous responses to seasonal burning in
experimental tallgrass prairie plots provides information on postfire response
of switchgrass in experimental prairie plots that was not available when this
species review was originally written.

More info for the terms: herb, rhizome

Rhizomatous herb, rhizome in soil

More info for the terms: competition, natural, rhizome, seed

Switchgrass reproduces both sexually and vegetatively. Rhizomes are
responsible for vegetative expansion, but spreading ability depends upon
growth form. Some rhizomes of sod-forming ecotypes may extend to
lengths of 1 to 2 feet (0.3-0.6 m), while those of bunch-forming
ecotypes may extend only a few inches [7,77]. The primary site of
nonstructural carbohydrate storage is in the stem bases, roots, and
rhizomes [72].

Switchgrass generally produces abundant seed. Natural stands often
yield 100 pounds of seeds per acre (112 kg/ha), and cultivated stands
may yield 300 to 500 pounds of seeds per acre (336-561 kg/ha) [78]. The
seeds are shed in fall or winter and require winter dormancy before they
germinate in the spring [61]. Germination begins when soil temperatures
reach 68 degrees Fahrenheit (20 deg C) [72]. Seed collected from
southeastern Montana and northeastern Wyoming had relatively high
germination rates; 70 to 90 percent at temperatures between 68 and 86
degrees Fahrenheit (20-30 deg C) [22]. Fulbright and others [26]
reported germinative capacity of 40 to 70 percent.

The importance of switchgrass seedling recruitment into prairie habitats
is scarcely discussed in scientific literature. In tallgrass prairie,
switchgrass tillering and rhizome production generally begins 5 to 7
weeks after germination, unless competition is severe [77]. Three
months after germination, plants may be 12 to 20 inches (30-50 cm) tall,
and roots may be 12 to 30 inches (30-76 cm) deep [77].

On sand dunes bordering Lake Erie, switchgrass maintains and expands
stands primarily through seedling establishment. On the dunes,
seedlings emerged from seeds buried at depths of 0 to 4.3 inches (0-11
cm) and withstood considerable postemergence sand burial [79].

More info on this topic.

More info for the terms: climax, seed

Obligate Climax Species

Switchgrass is a climax species of tallgrass prairie. It is slow to
establish on abandoned agricultural lands because of limited seed
dispersal distances and relatively high soil fertility requirements
[61].

The currently accepted scientific name of switchgrass is Panicum
virgatum L. [37,38]. Varieties are as follows:

P. v. var. cubense Griseb.
P. v. var. spissum Linder.
P. v. var. virgatum

More info for the terms: cover, restoration, seed, warm-season

Switchgrass is used for a variety of revegetation and erosion control
purposes. In the East, it is seeded alone or in mixture with other
native grasses on mine spoils where it typically requires 2 to 4 years
to develop a good ground cover [73]. Once established on graded and
contoured strip-mined lands in Kentucky, switchgrass can be used as
warm-season pasture or hayland [44]. In Iowa, it is seeded along rural
roadsides to provide erosion control and wildlife habitat [23]. It is
also commonly planted along waterways to provide erosion control and in
mixture with other native grasses for prairie restoration [67,74].

Switchgrass is popular for revegetation programs because the seed of
numerous cultivars is readily available, and stand establishment is
relatively easy [68]. The smooth seed should be planted with a drill to
a depth of 0.25 to 0.5 inch (0.6-1.2 cm) at a rate of three to six pure
live seeds per acre (3.4-6.7 kg/ha) [72]. Atrazine applied as a
preemergent herbicide effectively controls weeds and improves
switchgrass stand establishment [65,72].