BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Bouteloua gracilis | Blue Grama 



GENERAL BOTANICAL CHARACTERISTICS : 
Blue grama is a warm-season, native perennial [6,46].  This rhizomatous
grass typically forms thick, dense sod mats [8].  In the southern
portions of its range, however, blue grama is patchy rather than sodlike
in growth [47].  Its height varies from 12 to 16 inches (31-41 cm) in
the northern parts of its range to 24 to 30 inches (61-76 cm) in
southern portions of its range [47].  Plants are leafy at the base [4];
culms reach 7.9 to 23.6 inches (20-60 cm) [46].  Leaves are flat or
loosely involute [24].  Blue grama has numerous slender, erect flower
stalks with two to five spikes each [51].  Relatively little is known
about longevity of blue grama.  In a Nebraska study, a majority of
plants had died by the end of the third growing season [52].  Percent
survival was [52]:

                 Year 1            Year 2            Year 3
                  100%               66%               45%

Blue grama has an extensive, efficient, widely spreading root system.
The adundant roots grow from short rhizomes [8].  Fine, fibrous roots
are mostly concentrated near the soil surface, although some extend
deeper.  The majority of roots occur in the upper 13.8 to 29.5 inches
(35-75 cm) of the soil, with a few coarser roots extending to depths of
5 to 6 feet (1.5-1.8 m) [8,27].  In Saskatchewan 93 percent of the
underground parts of blue grama occurred in the upper 11.8 inches (30
cm) of soil; 84 percent occurred in the upper 5.9 inches (15 cm) [8].
Root depth is generally greater on less xeric sites [8].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte
   Geophyte


REGENERATION PROCESSES : 
Blue grama regenerates through rhizomes, seed, and tillers [8,51].  In
favorable years blue grama produces light seeds which germinate well in
warm, moist soil [6].  Seed is dispersed by wind, water, and animals
[50].  Rather specific temperature and moisture regimes are necessary
for germination.  Blue grama requires adequate surface soil moisture for
a 2- to 4-day period for germination and initial seminal root growth
[55].  It lacks lateral seminal roots, and seedlings die when the
surface soil dries out before the seminal root elongates to deeper soil
levels [54].  Rainy periods are often too short to permit germination,
or surface soils dry out too quickly for establishment [49].

Dung beetles bury blue grama seeds, which may facilitate germination.
In a Colorado study, germination was 20 percent for dung beetle-buried
seed, and 17 percent for control seed.  Seedlings have emerged from aged
(6-30 months), partially decomposed cattle dung in the Central Great
Plains [54].

Three critical factors for successful growth of blue grama seedlings are
(1) initiation of the seminal root, (2) moist soil until at least 6
weeks after emergence, and (3) initiation of adventitious roots [55].  A
second wet period of 2 to 4 days is required 2 to 8 weeks after
germination for the development of adventitious roots [19,55], which the
plant needs to survive the winter [54].  Temperature is also important.
Development is most rapid at 68 to 77 degrees Fahrenheit (20-25 deg C)
[20].  An average soil temperature above 59 degrees (15 deg C) is
necessary for good seedling establishment.  A soil water potential of
approximately -0.03 megaPascals in the 0- to 16-inch (0-40 cm) zone is
required during emergence [55].

Blue grama has developed numerous adaptations for seedling growth and
survival in extremely dry environments.  Seedlings can increase water
uptake, adjust leaf area, and reduce transpiration to avoid drought
[56].


SITE CHARACTERISTICS : 
Blue grama is widely distributed on dry, open grass or sagebrush plains,
ridges, foothills, and uplands throughout the West and the Great Plains
[4,10].  It occurs in pinyon-juniper and ponderosa pine woodlands to
middle elevations in the mountains and on well-vegetated floodplains,
washes, and benches [5,10].  Blue grama is also found on waste ground
and overgrazed pasturelands [8,21].

Blue grama grows well on sandy loam, sandy, or gravelly soils [10].  In
southeastern Arizona, it is most abundant on acidic, relatively
infertile sandy and clay-loam soils [37].  Soils are generally low in
available nitrate and/or phosphate [37].  Blue grama is well adapted to
growth in soils in which water percolates slowly [47].

Blue grama grows within the following elevational ranges [5,13]:

           from   4,000 to 8,000 feet (1,220-2,440 m) in AZ
                  3,500 to 10,500 feet (1,068-3,203 m) in CO
                  2,400 to 5,600 feet (732-1,628l m) in MT
                  3,200 to 9,500 feet (976-2,898 m) in UT
                  3,100 to 8,500 feet (946-2,593 m) in WY


SUCCESSIONAL STATUS : 
Obligate Climax Species

Blue grama is a climax dominant in shortgrass prairie [6].  It
intolerant of heavy shade [53].


SEASONAL DEVELOPMENT : 
Blue grama begins growing in May or June with the onset of summer rains
[46,47].  Growth is rapid under favorable conditions; plants mature in
60 to 70 days [47].  They generally reach 4 to 5 inches (18-28 cm) by
midsummer [50].  Growth is largely dependent on the amount of moisture
available before the beginning of hot summer weather [47].  In the
central Great Plains, blue grama produces flowers and seed within 60
days of the onset of new growth [49].

During drought periods blue grama is dormant, but greens up quickly
after moisture is received [10,47].  With sufficient fall precipitation,
it produces new growth, sometimes flowering a second [41,51] or, more
rarely, a third time [49].  Flowering times are as follows [14,21]:
 
     Location         Beginning of Flowering        End of Flowering

        CO                     July                     September
        MT                     July                     August
        ND                     July                     August
        WY                     July                     September
     Great Plains              June                     August

Related categories for Species: Bouteloua gracilis | Blue Grama