Blue grama accounts for most of the net primary productivity in the shortgrass prairie of the central and southern Great Plains. It is a green or greyish, low-growing, drought-tolerant grass with limited maintenance.[6]
Description
Blue grama grass in early summerThe comb-like spike in bloom in August, with white stigmas sticking out of the top and yellow anthers hanging belowMature spikelets that have detached from the spike. Each may contain a seed.
Blue grama has green to greyish leaves less than 3 mm (0.1 in) wide and 1 to 10 in (25 to 250 mm) long. The overall height of the plant is 6 to 12 in (15 to 30 cm) at maturity.[7]
The flowering stems (culms) are 7 to 18 in (18 to 46 cm) long. At the top are one to four, usually two,[8] comb-like spikes, which extend out at a sharp angle from the flowering stem.[7] Each spike has 20 to 90 spikelets.[7] Each spikelet is 5 to 6 mm (0.20 to 0.24 in) long, and has one fertile floret and one or two reduced sterile ones.[9] Below the florets are two glumes, one 1.5 to 3 mm (0.06 to 0.12 in) long and the other 3.5 to 6 mm (0.14 to 0.24 in) long.[9] The fertile floret has a lemma (bract) 5 to 5.5 mm (0.20 to 0.22 in) long, with three short awns (bristles) at the tip, and the sterile floret has a lemma about 2 mm (0.08 in) long with three awns about 5 mm (0.2 in) long.[8][10] If pollinated, the fertile floret produces an oblong-elliptic brown seed 2.5 to 3 mm (0.10 to 0.12 in) long.[11] When the seed is mature, the whole spikelet detaches, but the two glumes remain.
The roots generally grow 12 to 18 in (30 to 46 cm) outwards, and 3 to 6.5 ft (0.9 to 2.0 m) deep.[7]
Blue grama is readily established from seed, but depends more on vegetative reproduction via tillers. Seed production is slow, and depends on soil moisture and temperature. Seeds dispersed by wind only reach a few meters (6 ft); further distances are reached with insects, birds, and mammals as dispersal agents. Seedling establishment, survival, and growth are greatest when isolated from neighboring adult plants, which effectively exploit water in the seedling's root zone. Successful establishment requires a modest amount of soil moisture during the extension and development of adventitious roots.[7]
Established plants are grazing-, cold-, and drought-tolerant, though prolonged drought leads to a reduction in root number and extent. They employ an opportunistic water-use strategy, rapidly using water when available, and becoming dormant during less-favorable conditions. In terms of successional status, blue grama is a late seral to climax species. Recovery following disturbance is slow and depends on the type and extent of the disturbance.[7]
Distribution
Blue grama has the widest distribution of all grama grasses. It will grow on most soil types, and readily adapts to local conditions. It can be found as far north as Alberta, and as far south as Mexico. It is present in most of the Midwestern United States, extending east to Missouri and Texas, and as far west as Southern California. It has been introduced to some eastern states, as well as South America.[12]
Horticulture and agriculture
Blue grama is valued as forage, and is the most valuable grama. It is an ideal range grass in the southwest. It will survive heavy grazing and extreme drought, and is quite palatable to livestock.[12] Grazing of blue grama rangelands might also prevent invasion of undesirable weedy plants.[13]
Among the Zuni people, the grass bunches are tied together and the severed end is used as a hairbrush, the other as a broom. Bunches are also used to strain goat's milk.[16] The Costanoan, or Ohlone, use(d) the hollow stems as straws.[17] The Navajo use(d) it as sheep and horse feed.[18]
Ecology
Blue grama is the dominant species of the US shortgrass steppe ecoregion.[19][20] Populations of blue grama across the great plains are genetically differentiated (even at small spatial scales) and show functional trait variance connected to climate.[21][22][15] Blue grama from more arid grasslands are also characterized by greater phenotypic plasticity.[21]
^"Bouteloua gracilis". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014. Retrieved July 13, 2018.
^"Bouteloua gracilis". State-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014. Retrieved July 13, 2018.
^Smoliak, S.; Ditterline, R.L.; Scheetz, J.D.; Holzworth, L.K.; Sims, J.R.; Wiesner, L.E.; Baldridge, D.E.; Tibke, G.L. "Blue Grama (Bouteloua gracilis)". Montana Interagency Plant Materials Handbook. Montana State University Extension Service. Archived from the original on June 10, 2010.
^ abcdefAnderson, Michelle D. (2003). "Bouteloua gracilis". Fire Effects Information System (FEIS). US Department of Agriculture (USDA), Forest Service (USFS), Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved August 24, 2016.
^ abGould, Frank W. (1951). Grasses of Southwestern United States. Tucson: University of Arizona. p. 146. {{cite book}}: |work= ignored (help)
^Porensky, Lauren M.; Derner, Justin D.; Augustine, David J.; Milchunas, Daniel G. (2017). "Plant Community Composition After 75 Yr of Sustained Grazing Intensity Treatments in Shortgrass Steppe". Rangeland Ecology & Management. 70 (4): 456–464. doi:10.1016/j.rama.2016.12.001. S2CID90458063.
^Munson, Seth M.; Lauenroth, William K. (2009). "Plant population and community responses to removal of dominant species in the shortgrass steppe: Plant responses to removal of dominant species". Journal of Vegetation Science. 20 (2): 224–232. doi:10.1111/j.1654-1103.2009.05556.x.
