Big Bluestem

More info for the terms: density, fuel, meristem, tiller

Fires that occur during the the active growth stage in the summer are
most damaging to big bluestem because of the limited carbohydrate
reserves available for new growth during this time period [23].  Burning
tallgrass prairie in Oklahoma during late summer resulted in nearly
complete combustion of aboveground biomass [36].  On grazed plots with
little fuel accumulation, tillers were completely defoliated but did not
suffer apical meristem damage.  On ungrazed plots with heavy fuel
accumulation, tillers did suffer apical meristem damage.  Tiller density
was significantly lower 2 months after burning on these high fuel plots,
and new growth consisted largely of newly initiated tillers.

More info for the terms: cool-season, cover, density, tiller

Postburn herbage production indicates that the season of burning, the
amount of annual precipitation the area receives, and site conditions
greatly influence big bluestem's response to burning.  Big bluestem
increases as influenced by different annual burning dates in Kansas are
summarized below [123]:

           Kansas prairie burned annually 48 of 56 years

time of burning             percent big bluestem in the grass community
       
prestudy (unburned)                             16.7
poststudy (unburned)                            18
late spring, about May 1                        46
mid-spring, about April 10                      24
early spring, about March 20                    23
winter, about December 1                        35

Farther west, in the mixed-grass prairie which receives less
precipitation, big bluestem generally increases following fire if
precipitation is average or above average but decreases if drought
conditions occur.  Response is somewhat variable though, and dependent
upon site characteristics.  On upland sites in the mixed-grass prairie
where big bluestem occurs infrequently, it is generally not stimulated
by burning [115].  Big bluestem is more common on lowland sites, and
because lowlands receive some surface water runoff, burning these sites
in the spring results in increased big bluestem biomass [35,115].  In
the mixed-grass prairie of north-central South Dakota, big bluestem
production increased following spring burning on overflow sites, even
though 2 years of below average precipitation followed [35].  Results
from this study are summarized below:

                                                           current years
 burning     phenological       leaf          flower       growth (g/m2)
  date          state        length (cm)     stalks/m2      (air dried)
                             8/80   8/81    8/80   8/81        8/80

May 15, 1980   dormant      21.3   45.2     132.4  69.8        128.8
June 16, 1980  5-10 cm tall 16.8   37.0      95.2  53.8         71.4
control                     42.4   43.4       2.0  15.1         23.0

Fires that occur during the summer cause the most harm to big bluestem.
Summer burning during a below average precipitation year in
north-central South Dakota resulted in the reduction of big bluestem on
overflow sites, and shifted dominance towards cool-season grasses [115].
In the true prairie of Oklahoma, late summer burning resulted in initial
reductions of big bluestem tiller density; however, by the end of the
growing season, tiller density returned to normal [36].  Measurements
taken the following August showed that productivity was within the
seasonal normal range.  In the Black Hills of South Dakota, big bluestem
basal cover remained unchanged following an October burn [13], and
increased slightly following spring burning [41].

big bluestem
tall bluestem
turkey-foot

More info for the term: cover

The tall, coarse, upright vegetative structure of big bluestem, when
found in pure stands or when mixed with other tall and mid-height
grasses, provides excellent nesting and protective cover for smaller
wildlife species.  Big bluestem provides essential nesting cover for the
greater prairie chicken, lesser prairie chicken, ring-necked pheasant,
partridges, quail, dabbling ducks, the sedge wren and numerous other
song birds [17,43,59,112,127,138].  Big bluestem provides greatest
environmental protection during the summer but, because it is resistant
to flattening by snow, also provides protective cover during the winter.
Big bluestem provides important cover for at least 24 species of
songbirds that winter on the Konza Prairie in Kansas [38].

The degree to which big bluestem provides environmental protection
during one or more seasons for wildlife species in some western states
is as follows [17,38,59,66,92,114]:

                     IA    KS    MN    MO    ND    SD    WY 
Pronghorn           ----  ----  ----  ----  poor  ----  ----
Elk                 ----  ----  ----  ----  ----  ----  poor
Mule deer           ----  ----  ----  ----  good  ----  poor
White-tailed deer   ----  ----  ----  ----  good  ----  poor
Small mammals       ----  ----  good  ----  good  ----  fair
Small nongame birds ----  good  ----  ----  good  ----  fair
Upland game birds   ----  good  ----  good  good  ----  fair
Waterfowl           good  ----  good  ----  good  good  poor

More info for the term: warm-season

Big bluestem is a native, tall, erect, perennial, warm-season, usually
rhizomatous, sod-forming grass [47,117].  The flowering stalks are
stout, coarse, and solid, and can reach a height of over 10 feet (3 m)
in a favorable growing season [51].  The inflorescence consists of two
to six digitate racemes (most commonly three, hence one of its common
names "turkey foot") which are 2 to 4 inches (5-10 cm) long [47,117].
Spikelets are in pairs along the raceme axis and are approximately equal
in length (0.25 to 0.4 inch [7-10 mm]) [47,117,131].  One is sessile,
usually fertile, plump, and awned.  The other is pedicillate, sterile,
slender, and awnless [82,131].  Big bluestem stands display a variety of
colors from steel gray to wine red [14].

Rhizomes are generally 1 to 2 inches (2.5-5 cm) below the soil surface
but are common to a depth of 4 inches [3,133].  They are coarse, 0.1 to
0.2 inch (3-6 mm) thick, excessively branched, and are frequently
continuous for 6 to 10 inches (15-24.5 cm) [133].  These rhizomes form
an open network, which is branched by the multiple roots which arise
from them.  On mature plants, roots are coarse, with laterals extending
2 to 6 inches (5-15 cm) [133].  The main roots extend downward almost
vertically to depths of 6 to 10 feet (2-3 m), and taper very gradually
[132,133].  A large percentage of the roots are found in the A horizon
independent of soil type or horizon depth.  Seventy-eight to ninety
percent of root biomass has been found in A horizons ranging from 7 to
20 inches (18-50 cm) [136].

Big bluestem exhibits wide ecotypic variation.  It is generally shorter
at maturity in the northern portion of its range, and taller in the
southern portion of its range [59].  This variation may also be found
within a local area.  Weaver [132] observed flower stalks varying in
height from 3 feet (0.9 m) on moist slopes to 7 to 12 feet (2.1-3.6 m)
on rich bottomland sites.  Throughout the tallgrass and mixed-grass
prairie regions, big bluestem normally is a rhizomatous, sod-forming
grass.  But when found in more arid locations, or on drier slopes, its
appearance is more similar to a bunchgrass [132].

Big bluestem is widespread, occupying all but a few western states, but
it is most conspicuous in the tallgrass and mixed-grass prairie regions.
It is distributed across southern Canada from Quebec to Saskatchewan,
south through Montana and Wyoming to Arizona and northern Mexico, and
eastward to Florida and Maine [44,50,131,133].

More info for the terms: fire regime, grassland

Historically, fires occurred frequently in the tallgrass prairie and
were essential in maintaining these grasslands [23].  Across the Great
Plains, lightning-caused fires may have occurred as frequently as every
1 to 6 years [74].  Having evolved in a grassland environment subjected
to frequent fires, big bluestem is well adapted to fire.  After
aboveground foliage is consumed by fire, new growth is initiated from
rhizomes.  The well-developed rhizomes are generally 1 to 2 inches
(2.5-5 cm) below the soil surface [3,133].  In general, grassland fires
are of low intensity because the flames pass quickly, and the soil
temperature 1 inch (2.54 cm) below the surface rises very little [74].
Plants burned during the spring when dormant quickly send up vigorous
new growth because of stored carbohydrate reserves in belowground
organs.  If burned during the summer when plants are actively growing,
plants normally survive by initiating new growth from rhizomes; however,
regrowth may be slower and less vigorous than in plants burned when
dormant [36].

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: density, fire intensity, fire management, forest, fuel, meristem, prescribed fire, tiller, wildfire

Late spring is the best time to burn big bluestem stands.  The later in
the spring burning occurs, just prior to the emergence of new growth,
the greater the postburn herbage production will be.  If burns are
conducted too early, production may decrease as a result of the
increased evaporation of soil moisture in the interval between the fire
and the resumption of new growth [74].  Spring burns leave the soil
exposed for the least amount of time and thus reduce soil moisture
levels over the growing season less than winter, early, or mid-spring
burns [6,85].  Regardless of season of burn, however, soil moisture
content is consistently lower in burned areas than in unburned areas.
Thus in drought years, in areas of low precipitation, or in areas where
soil moisture is limiting, big bluestem will probably not show the high
postburn biomass increases generally reported for tallgrass prairie
sites.

Late spring burning can be used to increase grass productivity and
improve cattle use.  Cattle prefer vegetation on burned sites over that
on unburned sites [80].  Compared with weight gains of cattle grazing in
nearby unburned pastures, weight gains of cattle grazing on late spring
burned pastures were 17 percent higher in Oklahoma [115], and 11 percent
higher in Kansas [80].

Late spring burning can be used to increase big bluestem and other warm
season grass composition in warm season pastures or rangelands infested
with undesirable cool season grasses such as Kentucky bluegrass.  Late
spring burning favors warm season grasses because they are dormant at
the time of ignition, and resume growth as normal from stored food
reserves held in underground organs.  Burning at this time generally
harms cool season grasses, however, since they begin spring growth
earlier, and are actively growing at the time of ignition.

FIRE CASE STUDY
SPECIES: Andropogon gerardii
FIRE CASE STUDY CITATION :
Uchytil, Ronald J., compiler. 1988. Effects of different fuel loads on big bluestem
in an Oklahoma prescribed fire. In: Andropogon gerardii. In:
Fire Effects Information System, [Online]. U.S. Department of Agriculture,
Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory
(Producer). Available: https://www.fs.fed.us
/database/feis/ [
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months[0] = "January";
months[1] = "February";
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months[7] = "August";
months[8] = "September";
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months[10] = "November";
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var date = new Date();
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document.write(year+", "+months[month]+" "+day);
].


REFERENCE :
Ewing, A. L.; Engle, D. M. 1988. Effects of late summer fire on tallgrass
prairie microclimate and community composition. The American Midland Naturalist.
120(1): 212-223. [36].


SEASON/SEVERITY CLASSIFICATION :
Late summer/severe


STUDY LOCATION :
This study took place at the Oklahoma Agricultural Experiment Station's
Agronomy Research Range, approximately 9 miles (15 km) southwest of
Stillwater, Oklahoma.


PREFIRE VEGETATIVE COMMUNITY :
The vegetation was tallgrass prairie dominated by the big bluestem
(Andropogon gerardii), indiangrass (Sorghastrum nutans),
switchgrass (Panicum virgatum), little bluestem (Schizachyrium
scoparium), and side-oats grama (Bouteloua curtipendula).


TARGET SPECIES PHENOLOGICAL STATE :
Big bluestem was in an active growth stage at the time of this September
5 burn.  Plants were probably in flower.


SITE DESCRIPTION :
Two similar upland study sites with different grazing histories,
approximately 2.1 miles (3.5 km) apart, were burned.  One site was
moderately grazed in recent years including the year of burning
(considered the low fuel site), while the other had not been grazed for
at least 3 years (considered the high fuel site).  Mean annual
precipitation is 32.7 inches (83.1 cm) with 75 percent falling between
April through October.  Precipitation was 17 percent above average
during the 1985 growing season.  Weather conditions were typical of
wildfire conditions - hot and dry.  The relative humidity was 36
percent, while the ambient temperature was 98.6 degrees F (37 deg C).
Wind speed at the low fuel plots was 13.8-24 mph (23-40 kph), and 7.8-18
mph (13-30 kph) at the high fuel plots.  The low fuel plots had 443 plus
or minus 74 grams/m2 of accumulated fuel, while the high fuel plots had
1032 plus or minus 60 grams/m2 of accumulated fuel.


FIRE DESCRIPTION :
The fire was a line head fire ignited by drip torch on September 5, 1985.
Fire intensity and fire temperatures demonstrate that fire on the high
fuel plot was roughly four times as intense at the soil surface as that
on the low fuel plot.  Fire intensity and duration was measured in
degree seconds.  Degree seconds is the amount of time the sampled area
differs from the ambient post-burn temperature by more than 2 degrees C
(sampled at two second intervals).  Data on fire intensity and duration
are presented below:

   Area Sampled                              degree seconds
                                      low fuel            high fuel
soil surface                      10,400 +or- 1,900    43,000 +or- 3,200
6 in (15 cm) above soil surface    6,300 +or- 40       29,000 +or- 2,100
12 in (30 cm) above soil surface   3,900 +or- 180      20,300 +or- 1,400


FIRE EFFECTS ON TARGET SPECIES :
This late summer fire resulted in nearly complete combustion of biomass,
with the plots generally having blackened and bare soil with a dusting
of ash.  Tiller counts two months after the fire showed that big
bluestem recovered well on the low fuel plot.  Most of the regrowth came
from existing tillers which had been completely defoliated but had not
suffered apical meristem damage during the fire.  On the high fuel plot,
extensive damage to tillers occurred.  Reductions in tiller densities
were apparent 2 months after burning.  Regrowth on high fuel plots
consisted largely of newly initiated tillers.  Big bluestem tiller
density before and after burning is summarized below:

                              low fuel plot          high fuel plot
                       before burn  after burn   before burn  after burn
                        (8/15/85)   (10/22/85)    (8/15/85)   (10/22/85)

tiller density (#/m2)      23          45            89          17

By the end of the following growing season, tiller densities were
roughly equal on burned and unburned plots.  Even on the high fuel plot,
where fire induced reductions in tiller density was apparent in the
early growing season, tiller densities returned to normal by September.


FIRE MANAGEMENT IMPLICATIONS :
The rhizomatous character of big bluestem makes it well adapted to
survive summer fires.  Initiating new growth from rhizomes allows this
grass to quickly revegetate the postburn community.  Wildfire in the
tall grass prairie region, may initially reduce big bluestem
productivity, but total aboveground biomass may return to normal by the
end of the following growing season.

More info for the term: wildfire

The rhizomatous character of big bluestem makes it well adapted to
survive summer fires.  Initiating new growth from rhizomes allows this
grass to quickly revegetate the postburn community.  Wildfire in the
tall grass prairie region, may initially reduce big bluestem
productivity, but total aboveground biomass may return to normal by the
end of the following growing season.

More info on this topic.

More info for the term: geophyte

  
   Geophyte

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

Big bluestem occurs on a variety of sites throughout its range but
develops best on fertile silt and clay loam soils of lowlands.  Soil
moisture seems to be the most important factor determining big
bluestem's importance in a community.  It develops best on mesic sites
in the true prairie and mixed-grass prairie regions.  In the mixed-grass
prairie where precipitation is limited, it occupies ravines, lower
portions of gentle slopes, and well-watered lowlands where the soil
moisture content is high due to some surface runoff [3,135].  Along the
major rivers and their tributaries in the mixed-grass prairie, big
bluestem can comprise up to 90 percent of the vegetation over extensive
areas [135].  Here its chief associates are sideoats grama (Bouteloua
curtipendula), dropseeds (Sporobolus spp.), switchgrass (Panicum
virgatum), indiangrass (Sorghastrum nutans), and Canada wildrye (Elymus
canadensis).  Farther west toward the Rocky Mountains, big bluestem
becomes even more dependant upon mesic sites.  In the Rocky Mountain
foothills of eastern Wyoming, big bluestem was found only on
south-facing slopes of steep ravines, and always growing immediately
adjacent to large rocks which apparently acted as micro watersheds,
substantially increasing the usable soil moisture from summer rains
[49].

In the true prairie region, big bluestem occurs on upland sites and is
associated with little bluestem (Schizachyrium scoparium), but generally
comprises only 5 to 20 percent of the cover [133].  Big bluestem seems
to be less tolerant than little bluestem to low soil moisture.  This is
apparently due to big bluestem's deep, coarse, root system which is
effective at extracting moisture from the silty or clayey soils of sites
it usually dominates [79].  Even in the true prairie where precipitation
is abundant, big bluestem is most plentiful on low mesic sites
[58,122,133].  Here it is most often associated with two other
tallgrasses:  indiangrass (Sorghastrum nutans) and switchgrass (Panicum
virgatum).  In moist stands, individual stems in well-established sod
are spaced about 0.5 inch (1 cm) apart [108,132].  Yet the foliage is so
dense and spreading that light is reduced at the soil surface by as much
as 58 percent [70], making establishment of other species difficult.  In
drier habitats, big bluestem grows as a bunchgrass, occurring in
isolated bunches [32,108].  Big bluestem is shade tolerant, and its
leaves are able to remain green and function with only 5 to 10 percent
of full sunlight [108].

Big bluestem is believed to have been the prevailing grass present
during the formation of prairie soils [5].  These soils are generally
silt loam to silty clay loam with soil horizons greater than 10 inches
(25 cm).  Big bluestem grows best on fertile silt and clay loam soils of
lowlands and ravines but is also common on calcareous blackland soils
[131].  Generally it grows well in silty or clayey soils, fair in sandy
soils, and poor in gravelly soils or dense clay [126,132].  In Texas,
big bluestem frequency has been shown to be positively correlated with
percent clay and organic matter of soil [25].

Elevational ranges in some western states are as follows [28,42]:

        CO     3,400 to 9,500 feet (1,036-2,896 m)
        NM     3,500 to 9,000 feet (1,067-2,743 m)
        MT     3,300 to 4,000 feet (1,006-1,219 m)
        WY     3,600 to 9,000 feet (1,067-2,743 m)

More info on this topic.

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

     1  Jack pine
    14  Northern pin oak
    16  Aspen
    63  Cottonwood
    72  Southern scrub oak
   237  Interior ponderosa pine
   241  Western live oak

More info on this topic.

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):

   FRES15  Oak - hickory
   FRES17  Elm - ash - cottonwood
   FRES19  Aspen - birch
   FRES21  Ponderosa pine
   FRES32  Texas savanna
   FRES38  Plains grasslands
   FRES39  Prairie

More info on this topic.

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

More info for the term: forest

   K011  Western ponderosa forest
   K012  Douglas-fir forest
   K016  Eastern ponderosa forest
   K017  Black Hills pine forest
   K018  Pine - Douglas-fir forest
   K023  Juniper - pinyon forest
   K037  Mountain-mahogany - oak scrub
   K038  Great Basin sagebrush
   K056  Wheatgrass - needlegrass shrubsteppe
   K064  Grama - needlegrass - wheatgrass
   K065  Grama - buffalograss
   K066  Wheatgrass - needlegrass
   K067  Wheatgrass - bluestem - needlegrass
   K069  Bluestem - grama prairie
   K070  Sandsage - bluestem prairie
   K074  Bluestem prairie
   K075  Nebraska Sandhills prairie
   K076  Blackland prairie
   K079  Palmetto prairie
   K081  Oak savanna
   K082  Mosaic of K074 & K100
   K083  Cedar glades
   K084  Cross Timbers
   K086  Juniper - oak savanna
   K087  Mesquite - oak savanna
   K098  Northern floodplain forest

Under dry conditions, up to 100 percent of live and dead aboveground
stems and leaves may be consumed by fire [36,53].  Rhizomes, however,
usually survive, even when aboveground tissue is completely destroyed.

More info for the term: cover

Big bluestem provides both food and cover for numerous livestock and
wildlife species.  It is both palatable and nutritious, and livestock
often prefer it over other grasses on summer ranges [61,118].  Upland
game birds and songbirds eat the seeds [92].

More info for the term: climax

Big bluestem is characteristic of climax grasslands throughout the
tallgrass prairie region; farther west in the mixed-grass prairie region
it is a climax grass in well-watered lowlands.  It once blanketed the
tallgrass prairie, often comprising 70 to 90 percent of the vegetation
[108].

Published classification schemes listing big bluestem as a climax
indicator species or as a dominant part of the vegetation are presented
below:

Area          Classification                    Authority
----        ---------------------         ---------------------
KS          Grasslands                    Albertson 1937
MN          Tallgrass Prairie             Smeins and Olsen 1970
ND          Prairie Vegetation            Dix and Smeins 1967
            Tallgrass
Vegetation         Meyer 1985
            Grasslands                    Whitman and Wali 1975
NM          Pinyon-Juniper Woodlands      Kennedy 1983
TX          Prairie                       Collins and others 1975

More info for the term: graminoid

Graminoid

Big bluestem can withstand considerable grazing, but if continually
grazed closer than 6 to 8 inches (15-20 cm) during the growing season,
it will be replaced by less desirable grasses [118].  Bluestem ranges
have traditionally been grazed during the summer.  Research in Kansas,
however, shows that both continuous and deferred rotation grazing
systems can be used effectively [80].

Big bluestem hay should be cut in early summer to midsummer to ensure
high nutritive quality and to allow adequate time for plants to
replenish carbohydrate reserves before the first killing frosts.
Following cutting, livestock grazing should be excluded until after fall
frost; this allows stands to retain good vigor and productivity [80].

Nutritional value of big bluestem varies seasonally.  During spring and
summer, it provides high-quality forage, but as the growing season
advances, protein levels decrease significantly [87,88,89].  The
combination of its chemical composition and high palatability, however,
make big bluestem a superior quality summer forage.  It should be cut
for hay in early to midsummer, before the nutritive quality decreases.

Big bluestem plants collected in Nebraska and North Dakota showed the
following seasonal changes in nutrition [52,88]:

                             %Crude   %Crude    %Crude     Nitrogen Free
Location    Date     Ash     Protein   Fiber      Fat         Extract

Nebraska  6/26-7/5   10.7     14.46    30.65     2.99         41.19
N. Dakota   8/14     5.61     5.54     30.96     ----         40.03
Nebraska  mid-Sept   7.14     5.31     38.26     2.31         46.98

Seasonal trends in protein and in vitro dry matter digestibility (IVDMD)
of big bluestem plants from Nebraska are given below [89]:

Collection Date     Crude Protein      IVDMD

  mid-June             14.4%            62.2%
 late June              10.6%            ----
  mid-July               8.7%            ----
early October            7.0%            34.9%

     AL  AZ  AR  CO  CT  DE  FL  GA  HI  IL
     IN  IA  KS  KY  LA  ME  MD  MA  MN  MS
     MO  MT  NE  NH  NJ  NM  NY  NC  ND  OH
     OK  PA  RI  SC  SD  TN  TX  UT  VT  VA
     WV  WI  WY  MB  ON  PQ  SK  MEXICO

More info for the term: forbs

Big bluestem along with other native grasses and forbs has been used to
develop small prairie plantings for use in residential landscaping.  In
these small plantings, plants are seeded in mixtures to approximate the
temporal and physical structure of regional native prairie communities
[27].

Big bluestem is highly palatable to all classes of livestock during
spring and summer, with new growth being particularly palatable
[61,118,132].  Palatability decreases as the grass cures, and big
bluestem is probably only of fair palatability during the winter.  The
relish and degree of use shown by livestock and wildlife species for big
bluestem in several western states is as follows [28,61,92,118,141]:


                     CO    KS    MT    NE    ND    SD    TX    WY  

Cattle              good  good  good  good  good  good  good  good
Sheep               good  good  good  good  good  good  good  good
Horses              good  good  good  good  good  good  good  good
Pronghorn           ----  fair  ----  ----  poor  ----  ----  fair
Elk                 ----  ----  ----  ----  ----  good  ----  poor
Mule deer           ----  ----  ----  ----  poor  ----  ----  poor
White-tailed deer   ----  ----  ----  ----  poor  ----  poor  fair
Small mammals       ----  fair  ----  ----  ----  ----  ----  fair
Small nongame birds ----  fair  ----  ----  ----  ----  ----  fair
Upland game birds   ----  fair  ----  ----  ----  ----  ----  fair
Waterfowl           ----  ----  ----  ----  ----  ----  ----  poor

More info on this topic.

More info for the terms: cool-season, seed, tiller, warm-season

Big bluestem grows very rapidly, producing large amounts of foliage in
just a few short months.  A warm-season grass, big bluestem begins
growing in mid to late spring, several weeks after cool-season grasses.
As the season progresses, plants develop a dozen or more leaves from a
central tiller [105].  In Kansas, new growth begins between April 15 and
May 1, and by early July heavy foliage often exceeds 20 inches (50 cm)
[3].  Under favorable conditions, leaves may grow 0.75 inch (2 cm) a
day, attaining a mature height of 2.5 to 3 feet (0.75-0.9 m) by
midsummer [133,134].  After vegetative growth is complete, the flower
stalks begin to develop, and elongate 1.5 to 3 inches (3.8-7.6 cm) per
day [133].  Most flower stalks are produced in mid to late summer, with
plants from the northern portion of big bluestem's range flowering
earlier than those from the southern.  During a drought, discontinuous
flowering may occur.  In Illinois, a drought in July and early August
caused the tips of the culms to die back.  But following rains of above
normal precipitation in August, new inflorescences developed on the
culms below the withered ones [64].

The timing of nine phenological stages for eight varieties (cultivars or
test seed) of big bluestem are shown below [95].

Phenological stage:

1.  First emergence of inflorescence, 10 culms or more
2.  First anthesis, 10 culms or more
3.  Fifty percent emergence of the inflorescence
4.  Fifty percent anthesis
5.  First seed mature
6.  Fifty percent seed maturity
7.  Seed mature - starting to shatter
8.  Most seed shattered
9.  Complete dormancy

Phenolog. stage   1     2     3     4     5     6     7     8     9

origin   seed                                      
nw MN   ND-3784 Jul 11  14    19    27  Aug 20  29   Sep 4  14  Oct 13
nw MN   ND-3785 Jul 12  15    22    30  Aug 20  29   Sep 4  15  Oct 15
   ND   ND-4    Jul 13  14    22    29  Aug 18  Sep 2  14   29  Oct 15
   SD  'Bonilla'Jul 27 Aug 1  18    23  Sep 11  29   Oct 9  ---   ---
   SD   SD-43   Aug 9   10    18    29  Sep 24  ---   ---   ---   ---
   NE  'Champ'  Aug 13  13    27    30    ---   ---   ---   ---   ---
   NE  'Pawnee' Aug 16  16  Sep 4    7    ---   ---   ---   ---   ---
   KS  'Kaw'    Aug 31 Sep 2  13    16    ---   ---   ---   ---   ---

Flowering times for several states are as follows [28,71,94,114,134]:

Location        Beginning of flowering       End of flowering

  CO                    July                     Sept
  IL                    July                     Aug
  IO                    July                     Sept
  KS                    July                     Sept
  MO                    July                     Sept
  MT                    Aug                      Sept
  ND                    July                     Aug
  NE                    July                     Sept
  SD                    July                     ----
  WY                    July                     Sept

More info for the terms: density, fire interval, herbaceous, litter, rhizome, seed, warm-season

Big bluestem initiates new growth from surviving rhizomes after
aboveground foliage has been damaged or consumed by fire.  After summer
burns, depending on the amount of damage inflicted, regrowth is either
from undamaged apical meristems or from the initiation of new tillers
from underground rhizomes [36].  Plants burned during the spring or fall
when the aboveground foliage is dead resume growth in the spring as
normal.  In general, spring burning has a stimulating effect on the
growth and competitive vigor of big bluestem [74].

Big bluestem plants in recently burned areas start growth earlier in the
spring, develop faster, and produce more herbage than plants in unburned
areas.  This earlier and increased growth is most often attributed to
increased solar radiation reaching the soil following the removal of
standing dead material [53,56,69,70,94,102] which results in higher soil
temperatures [76,100].  Following spring burning in native bluestem
prairie in Missouri, soil surface temperatures in burned areas compared
to unburned area averaged 7.1 degrees F (3.9 deg C) warmer in April,
11.4 degrees F (6.3 deg C) warmer in May, 8.3 degrees F (4.6 deg C)
warmer in June, and 7.1 degrees F (3.9 deg C) warmer in July [76].
Increased soil temperatures promote earlier root growth and activity and
thus earlier emergence of shoots [72,99,106].  Also, the emerging shoots
receive more sunlight because they are not shaded by the standing dead
shoots and leaves of the previous year.  Knapp [69] reported that
following spring burning in Kansas tall grass prairie, big bluestem had
a greater photosynthetic rate and increased stomatal conductance and
leaf thickness in response to increased solar radiation.

In the tallgrass prairie, late spring burning, when warm-season grasses
are about to resume growth, is the most beneficial to big bluestem.  Big
bluestem stands burned at this time show the highest aboveground biomass
gains compared to unburned stands or stands burned at other times of the
year [4,8,123].  In the true prairie region, spring burning of big
bluestem stands that have not been burned within the past few years
almost always results in increased yields.  Two to three fold increases
are common [46,53,76,94,99,125].  Increases in big bluestem growth
following late spring burning are associated with increases in (1) the
density of tillers [53,68,121], (2) root and rhizome biomass [46], and
(3) size and number of leaves [4,69,70,121].

Increased flower stalk production is also common following burning
[21,32,33,46,54,94].  Following burning in Wisconsin, flower stalk
production increased six-fold [21]; after a spring burn in Iowa, flower
stalk production increased seven fold but returned to normal by the
third postburn growing season [32].  Although numerous researchers
report dramatic increases in seed production, Abrams [1] observed that
seedlings were less frequent in areas burned annually or on a 4-year
cycle than in unburned areas.

Big bluestem rapidly produces large amounts of foliage following fire.
Generally, it takes 2 to 5 years after burning for litter accumulation
to equal that of unburned areas [23].  When the fire interval is greater
than about 5 years, bluestem prairie becomes unproductive because the
large accumulations of standing dead material stifle growth.  However,
fires occurring more frequently than every 2 years will probably lower
biomass production.

The Research Project Summary, Herbaceous responses to seasonal burning in
experimental tallgrass prairie plots provides information on postfire response
of big bluestem 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: adventitious, cover, rhizome, seed, tiller

Although big bluestem is capable of both vegetative and sexual modes of
regeneration throughout its range, vegetative regeneration is most
prevalent.  Vegetative regeneration occurs with the initiation of growth
from rhizomes.  Parent tillers consist of a rhizome, four to six
adventitious roots, and an aerial shoot, and develop mature buds in leaf
axils on their rhizomes [84].  New tillers begin as buds on the rhizomes
of their parent tillers.  These buds grow horizontally from their parent
before emerging from the soil surface.  In Kansas, rhizome buds begin to
swell and break open in late March, and by the end of April, growth of
tillers and elongation of the rhizomes occurs and continues throughout
the summer until August [105].  McKendrick and others [84] observed that
each tiller averaged two tiller offspring during the succeeding growing
season, with about half of these second-year tillers being vegetatively
reproductive but producing no seed.  Once a clone is produced, it can
live and reproduce for an unknown number of years, perhaps centuries
[105].

In undisturbed stands only a small proportion of tillers flower each
year.  This has been attributed to the irregularity of moisture and
temperatures at blooming time [51,68].  Drought
severely reduces
flowering, but flowering increases during a wet year following a
drought.  Big bluestem also flowers abundantly following fire [68].

Abrams [1] found only 2.5 viable seeds per 1,352 cubic centimeters of
soil in undisturbed stands where big bluestem comprised 77 percent of
the canopy cover.  This almost total absence of buried seeds suggests a
high dependence on vegetative reproduction.  The limited germination in
big bluestem may be attributed to the following:  (1) seed predation by
birds, mammals, or insects either after having fallen or while still on
the plant; (2) fungus and bacteria during wet seasons which cause the
seeds to rot; and (3) the very limited space for germination in prairie
stands.  Carter and others [16] reported that 40 percent of the seed
crop of the big bluestem cultivar 'Pawnee' was destroyed by a midge in
certain seed production fields.  This midge is widespread in North
America and occurs in many areas where native stands of big bluestem
remain.

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):

    7  Lower Basin and Range
    9  Middle Rocky Mountains
   10  Wyoming Basin
   11  Southern Rocky Mountains
   12  Colorado Plateau
   13  Rocky Mountain Piedmont
   14  Great Plains
   15  Black Hills Uplift
   16  Upper Missouri Basin and Broken Lands

Late summer/severe

More info for the terms: fuel, wildfire

Two similar upland study sites with different grazing histories,
approximately 2.1 miles (3.5 km) apart, were burned.  One site was
moderately grazed in recent years including the year of burning
(considered the low fuel site), while the other had not been grazed for
at least 3 years (considered the high fuel site).  Mean annual
precipitation is 32.7 inches (83.1 cm) with 75 percent falling between
April through October.  Precipitation was 17 percent above average
during the 1985 growing season.  Weather conditions were typical of
wildfire conditions - hot and dry.  The relative humidity was 36
percent, while the ambient temperature was 98.6 degrees F (37 deg C).
Wind speed at the low fuel plots was 13.8-24 mph (23-40 kph), and 7.8-18
mph (13-30 kph) at the high fuel plots.  The low fuel plots had 443 plus
or minus 74 grams/m2 of accumulated fuel, while the high fuel plots had
1032 plus or minus 60 grams/m2 of accumulated fuel.

More info on this topic.

More info for the terms: climax, grassland

Obligate Climax Species

Self-perpetuating stands of big bluestem are indicative of climax
grassland communities.  Its ability to dominate the prairie is due to its
rapid growth, dense sod-forming habit, great stature, and shade
tolerance [108,132].

Andropogon gerardii Vitman var. gerardii [44,63,137]

The scientific name of big bluestem is Andropogon gerardii Vitman (Poaceae)
[10,19,45,50,143].

There is disagreement over the taxonomic treatment of the the
grasses traditionally known as big bluestem (Andropogon gerardii Vitman)
and sand bluestem (Andropogon hallii Hack.). These two bluestems are
recognized either as distinct species [10,19,45,50] or as varieties
within a single species [44,63,101,137]. Artificial hybridization
experiments have shown that these two bluestems are completely
interfertile [101], with offspring showing intermediate morphological
characteristics [45,101]. These two bluestems, however, show clear
ecological differences: big bluestem is widely distributed in North
America on moist prairie sites, while sand bluestem is restricted to
drier, sandy soils in the Great Plains [10]. Where their ranges
overlap, they freely interbreed. In the Nebraska Sandhills, big
bluestem occurs only in low meadows, while sand bluestem is restricted
to upland sand dunes. Hybrids are found in narrow zones 16 to 33 feet
(5-10 m) wide at the dune-meadow interface [10].

More info for the term: seed

Big bluestem has been seeded with other native prairie species to
restore disturbed prairie sites.  Many states have successfully
reconstructed prairies for scientific, educational, and aesthetic
purposes [22,112].  Big bluestem has also been planted by managers
attempting to reestablish native prairie vegetation along highways [90].

Big bluestem is not widely used for revegetating mine spoils; it has
shown varying success on different spoil material [8,48,78].

For rehabilitation purposes, cultivars released for the area should be
used.  Cultivars planted in areas with similar climatic conditions and
not more than 300 miles (500 km) north or 180 miles (290 km) east, west,
or south of their origin generally perform well.  Seed can be purchased,
or gathered locally in the early fall by hand picking or combining.
Local sources include railroad rights-of-way, backcountry roads, and old
cemetaries [110].  Commercially available big bluestem cultivars include
[9,15,59,131]:

'Bonilla' - originates from Bonilla, South Dakota.  It is recommended for
use in North Dakota, South Dakota, and Minnesota.  It exhibits early
maturity and early winter hardiness.

'Champ' - originates from Iowa and northern Nebraska.  It was developed
from interbreeding big bluestem and sand bluestem.  This is an early
maturing cultivar recommended for use from Nebraska south into Kansas,
and eastward on favorable sites.

'Kaw' - originates from the Flint Hills of Kansas.  This is a tall,
leafy, late maturing cultivar recommended for use from central Nebraska
south through Oklahoma.

'Pawnee' - originates from Pawnee County, Nebraska.  This is a late
maturing cultivar recommended for use from central Nebraska south
through Oklahoma.

'Rountree' - originates from west-central Iowa.  This cultivar is
resistant to leaf rust and has high forage production. It is recommended
for use throughout Missouri, Iowa, and southern Illinois.

'NDG-4' - is being developed from seed collected in North Dakota for
possible use throughout the Northern Great Plains.

For planting guidelines refer to Wasser [131], Reis and others [106],
McGinniesand Hassell [83], Oaks [91], Vogel [129], and Woehler [140].

Perennials, Terrestrial, not aquatic, Rhizomes present, Rhizome short and compact, stems close, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes solid or spongy, Stems with inflorescence less than 1 m tall, Stems with inflorescence 1-2 m tall, Stems with inflorescence 2-6 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath hairy, hispid or prickly, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blades mostly glabrous, Leaf blades more or less hairy, Leaf blades scabrous, roughened, or wrinkle d, Ligule present, Ligule an unfringed eciliate membrane, Ligule a fringed, ciliate, or lobed membrane, Inflorescence terminal, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence a panicle with narrowly racemose or spicate branches, Inflorescence a panicle with digitately arranged spicate branches, Inflorescence with 2-10 branches, Inflorescence branches paired or digitate at a single node, Inflorescence branches paired racemes, V-shaped, Flowers bisexual, Flowers unisexual, Spikelets pedicellate, Spikelets sessile or subsessile, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 2 florets, Spikelets paired at rachis nodes, Spikelets in paired units, 1 sessile, 1 pedicellate, Pedicellate spikelet well developed, staminate, Spikelets bisexual, Spikelets unisexual, Inflorescence disarticulating between nodes or joints of rachis, rachis fragmenting, Spikelets disarticulating below the glumes, Spi kelets falling with parts of disarticulating rachis or pedicel, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes equal to or longer than adjacent lemma, Glumes keeled or winged, Glume surface hairy, villous or pilose, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma 1 nerved, Lemma 3 nerved, Lemma glabrous, Lemma apex dentate, 2-fid, Lemma mucronate, very shortly beaked or awned, less than 1-2 mm, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn less than 1 cm long, Lemma awn 1-2 cm long, Lemma awn from sinus of bifid apex, Lemma awn twisted, spirally coiled at base, like a corkscrew, Lemma awn once geniculate, bent once, Lemma margins thin, lying flat, Lemma straight, Callus or base of lemma evidently hairy, Callus hairs shorter than lemma, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis.