BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Schizachyrium scoparium | Little Bluestem 



GENERAL BOTANICAL CHARACTERISTICS : 
Little bluestem is an erect, native, warm-season, perennial,
solid-stemmed grass; it exhibits both a bunch and sod-forming habit
[5,74,144,146,149].  On wet sites it may form an open or loose sod from
short rhizomes connecting small tufts which are close together.  More
often though, it is found under dry conditions where it forms distinct
clumps, usually 4 to 10 inches (10.1-25.4 cm) in diameter and 5 to 10
inches (12.7-25.4 cm) apart [5,146,150].  Even in pure stands on upland
sites, it will maintain this bunch type appearance with bare spaces
between the plants [74].  In Nebraska, plants commonly have 100 to 300
stems crowded into a 4-inch (10.1 cm) diameter bunch [149].  The flat,
slender leaves are 8 to 14 inches long (20.3-35.5 cm) at maturity and
spread to twice the area of the base [69,146].  Leaf height depends on
soil fertility and available water.  Leaves may reach a height of 20
inches (50.8 cm) on southern wet sites, but only 3 to 5 inches (7.6-12.7
cm) on southern xeric sites [69,146].  During dry years height may be
reduced by two-thirds [150].  On low mesic sites in the tallgrass
prairie, where it is often in competition with tallgrasses, little
bluestem can reach a height of 2 to 3.5 feet (0.5-1.5 m) [69,132,133].

The inflorescence is a slender raceme 1 to 2 inches (2.5-5 cm) long;
several racemes occur on each stem [59,77,133,149].  Spikelets occur in
pairs on a central unbranched axis.  One is sessile and contains a bent
awn about 0.5 inch (1.2 cm) long; the other is pedicellate and sterile.
Raceme axis joints and spikelet stalks are fringed with white, silvery
hairs, which give the seed stalks a fluffy white appearance at maturity
[59,74].  With the many culms thickly grouped, these silvery hairs make
the whole top of the plant resemble a man's gray beard (hence the old
common name of prairie beardgrass).  The leaves are light green during
spring and summer, but at maturity both leaves and stems turn a
reddish-brown [5,150].  

Roots are relatively fine.  Diameters range from 0.004 to 0.04 inch
(0.1-1 mm).  Roots extend laterally from the base of the crown, but the
bulk run almost vertically downwards to depths of 4.5 to 5.5 feet
(1.3-1.75 m) [146,149].

The growing points (apical meristem) reach a height of slightly over 1
inch (2.54 cm) above the soil surface [15].  Little bluestem has a very
high ratio of fertile to vegetative stems.  Plants with growing points
higher than 1 inch (2.54 cm) above the ground are more succeptible to
grazing damage than plants with growing points at or near the ground
surface.  At 1 inch the growing point may be removed by grazing, and
therefore no new leaves reproduced by the stems.  This in part explains
why under heavy grazing little bluestem is replaced by the common
associate side-oats grama (Bouteloua curtipendula), which has a growing
point at or near the soil surface.

Due to its broad distribution, little bluestem exibits varying degrees
of ecotypic variation.  Plants vary in height, length of leaves, time of
flowering, and clump diameter.  Miller [97] observed that the maximum
growth height and the amount of herbage produced was greater in plants
originating from areas with a longer growing season.  Little bluestem
plants (var. frequens) in Kansas subjected to long-term grazing by
cattle were observed to have shorter and narrower leaf blades, and
tillers of lower weights than plants from ungrazed populations [22].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte


REGENERATION PROCESSES : 
Little bluestem reproduces sexually by means of seeds, and vegetatively
by tiller expansion or through the initiation of new growth via short
inconspicuous rhizomes [146].

Branson [15] reported that about 75 percent of little bluestem stems
produce flowers, the highest of eight grasses studied.  Seeding habits
appear to be good, except during drought years when inflorescences may
fail to develop [15,137,150].  On Nebraska prairie sites under intense
competition from tallgrasses, little bluestem flowered regularly only
during wet years [131].  On uplands where competition was less severe,
little bluestem flowered more regularly [131].  Germination in the field
appears to be low, with seedling numbers low or absent.  In the
northeastern United States, buried viable seeds have been found in
37-year-old pine plantations where no parent plants occurred [89].  In
the West, however, no viable seeds have been found buried in the soil
[1,88,114].  Seed is generally dispersed only short distances from the
parent plant.  A maximum dispersal of only 5 to 6 feet (1.5-1,8 m) was
observed with wind speeds reaching 18 miles per hour (30 k/h)
[72,147,148].  Roos and Quinn [123] reported that insect predation of
spikelets was high in New Jersey.  Many fertile spikelets contained
insect larvae or were empty with no larvae or caryopsis.

Pure seed averages approximately 225,000 to 250,000 per pound
(496,000-551,000/kg) [50,127,144].  Optimum germination occurs at
temperatures from 68 to 86 degrees Fahrenheit (20-30 deg C) [127].
Under laboratory conditions, seeds germinated in 28 days after
prechilling [144].


SITE CHARACTERISTICS : 
Little bluestem is most abundant in prairie and plains grasslands
ecosystems.  It typically occurs on dry upland sites including
hillcrests, drier midslopes, level uplands, shallow ravines, and along
ridges and hillsides [5,7,28,38,39,136,137,145,147,151,155].  Little
bluestem also occurs in prairie fens where it is a codominant with big
bluestem [108].  These are areas of sapric peat soil constantly
saturated with artesian groundwater and are typically dominated by
prairie grasses. Prairie fens occur across glaciated terrain in
northeastern Illinois, southeastern Wisconsin, southwestern Michigan,
Indiana, western Ohio, and Missouri.

Climate:  Little bluestem occurs in areas receiving 10 to 40 inches
(250-1020 mm) of mean annual precipitation (MAP).  Optimal growth occurs
in areas with 20 inches (510 mm) of MAP, with good growth in areas with
15 to 20 inches (340-510 mm) of MAP [144].

Soils:  Little bluestem is adapted to soils ranging from sandy to
clay-loam in texture [10,37,127,136,154,155].  In eastern Kansas, little
bluestem made up 28 percent of the vegetation on uplands with a medium
or loamy soil texture, 16.5 percent on very shallow clay uplands, and
only 6.4 percent on upland clay pan soils [7].  Farther west, it occurs
on weakly developed soils of xeric uplands [127].  In western Kansas,
little bluestem communities are apparently partially restricted by
shallow soils [5].

Water relations:  Little bluestem is indicative of dry habitats and is
moderately drought resistant [144].  It can adjust osmotically to water
stress better than mesic species can.  Knapp [81] observed that little
bluestem experienced lower predawn and midday leaf osmotic potentials
than both switchgrass (a low elevation mesic grass) and big bluestem ( a
low to mid elevation mesic grass), indicating that little bluestem is
able to remain physiologically active longer under low soil moisture
than either of these grasses.  This is consistant with Mueller and
Weaver [100] who found that seedlings of little bluestem were less
drought resistant than seedlings of grama grasses (Bouteloua spp.), but
more drought resistant than seedlings of big bluestem, switchgrass,
indiangrass, junegrass (Koeleria cristata), wild rye (Leymus cinereus),
and western wheatgrass (Pascopyrum smithii).  Extended periods of
drought, however, appear to be detrimental to little bluestem.  In
Kansas during severe drought years in the 1930's, it was largely
replaced by sideoats grama [5,151].

Plant associates:  Common associates include big bluestem, indiangrass,
sideoats grama, porcupine grass (Stipa spartea), prairie dropseed
(Sporobolus heterolepis), blue grama, needle-and-thread (Stipa comata),
Indian ricegrass (Oryzopsis hymenoides), sand bluestem, and prairie
sandreed [7,140,144,147,148].

Elevation:  Elevational ranges for several western states are presented
below [37,53,68,135,153].

          above 4,000 feet (1,219 m) in AZ
           from 3,500 to 9,500 feet (1,067-2,896 m) in CO
           from 2,100 to 4,800 feet (640-1,463 m) in MT
           from 3,000 to 9,000 feet (914-2,743 m) in NM
          below 5,475 feet (1,668 m) in SD
           from 3,500-7,500 feet (1,067-2,290 m) in UT
           from 3,400-7,400 feet (1,036-2,256 m) in WY


SUCCESSIONAL STATUS : 
Facultative Seral Species

Little bluestem commonly occurs as a climax species on xeric sites in a
number of grassland communities in the western United States.  It can
also occur in seral stages.  It is a midseral species on sand blowouts,
often following sand bluestem [19].  It is one of the first plants to
invade cattle trails and road cuts bared by step erosion [63].

In the eastern United States, little bluestem is often a component of
early seral stages of deciduous or pine-deciduous forests, where it has
been found in oldfields 1 to 60 years old [123].  As woody vegetation
increases and dominates these sites, increased shading causes a rapid
decrease in the number and vigor of bluestem plants.  Little bluestem
seeds may remain viable in the understory of forests for decades; plants
may also persist.  Livingston and Allessio [89] found viable buried
seeds of little bluestem in 37-year-old pine plantations of the
northeastern United States where no parent plants occurred.  In areas of
savannah or prairie-forest ecotones, such as in Wisconsin and Ohio,
little bluestem is a climax dominant in the prairie areas.  Some of
these areas have now become overgrown with trees due to fire
suppression, yet little bluestem has persisted in very low numbers in
the understory.  In Ohio, Knoop [83] observed little bluestem growing in
oak woodlands adjacent to prairie remnants, where it had a frequency of
4.5 percent.  Holtz and Howell [65] observed that when the trees were
removed from a 70-year-old woodland in south-central Wisconsin dominated
by black oak (Quercus velutina) and black cherry (Prunus serotina),
little bluestem, which was in the understory, became a dominant part of
the prairie vegetation that followed.  Generally little bluestem plants
survive fire and become part of the early postfire community [159].


SEASONAL DEVELOPMENT : 
Little bluestem begins growth in late spring after cool-season grasses
have already developed.  In Oklahoma, little bluestem began growth about
20 days earlier than big bluestem [4].  Little bluestem begins growth in
early april in Oklahoma, late April in South Dakota, early May in North
Dakota, and late May in Montana [56,74,127].

Using stored carbohydrates, new shoots develop from axillary buds below
the ground surface.  Little bluestem starts growth in the spring with
only a few leaves but then fills out rapidly.  Culms initiating flower
development in Oklahoma had seven to eight leaves about 75 days after
initiation of new growth in the spring [120].  After 75 days, culms had
up to 17 leaves.  Shoots and inflorescences develop rapidly.

Little bluestem shows considerable ecotypic variation in relation to the
time of flowering [68,78,93,94].  Miller [97] observed that little
bluestem phenology follows a well-defined pattern, in which the date of
anthesis and the period of active growth are directly related to the
length of the growing season.  This pattern was also noted by McMillan
[93,94], who found that plants of northern and western origin flowered
earliest (usually July), while plants of southern and eastern origin
flowered later (around October).  Plants are genetically programmed to
flower with a particular photoperiod.  Plants from northern origins
mature under long day lengths and a short frost-free period.  Plants
from southern origin are adapted to shorter day lengths and a long
frost-free period.  This requirement remains constant, even when a
variety is moved from its original location.  The time of flowering in
several states is as follows [4,5,37,56,74,120,131,137]:

Location        Begining of Flowering        End of Flowering

  KS                 August                      September
  MT                 July                        August
  ND                 early August                September
  NE                 August                      September
  OK                 August                      September
  SD                 August                      ------
  TX                 August                      December
  WY                 August                      September

Earliest observed dates for different phenological events in North
Dakota are given below [56]:

    Phenological Stage                Date

Initiation of fruiting stalk          6/30
Seed head emergence                   7/19
Anthesis                              8/2
Leaf tip drying                       7/24
Leaves 0-25% dry                      9/5
Leaves 25-50% dry                     8/26
Leaves 50-75% dry                     9/7
Seed reaches maturity                 8/18
Seed begins to shed                   8/30

Severe frost ends the growing season and causes dormancy [5].  However,
in southern latitudes plants may not go completely dormant.  In Texas,
Dyksterhuis [41] observed that although plants appeared dormant, new
shoots continued to originate at the base from October to December, and
portions of the plant remained green throughout the winter.  During fall
and winter, a portion of total nitrogen is translocated belowground.
Adams and Wallace [3] found that at the time of flowering, aboveground
plant parts had 55.6 percent nitrogen compared with 44.4 percent in
belowground organs.  After the growing season, these values changed to
35.6 percent in aboveground parts, and 64.4 percent in belowground
organs.

Related categories for Species: Schizachyrium scoparium | Little Bluestem