Bouteloua curtipendula (Side-oats Grama)

Plant Info
Also known as:
Genus:Bouteloua
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
Habitat:sun; dry sandy or rocky soil; prairie, open woods, rocky slopes, bluffs, railroads
Fruiting season:June - August
Plant height:1 to 3 feet
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Cluster type: raceme Cluster type: spike

[photo of flowering spikes] From 12 up to 70 spreading to pendulous spikes on a 4 to 12-inch, erect to arching stem. Spikes are alternate along opposite sides of the stem, though may appear to be all on one side. Spikes are compact, 8 to 20 mm long with 3 to 7 (10) spikelets (flower clusters) crowded into two rows, to one side of a short flat rachis (stalk). Spikelets are 5 to 10mm long, each with a single fertile, perfect (both male and female parts) floret (flower) and 1 sterile floret, occasionally 2. Fertile florets are showy, with bright yellow, orange-red or dark purple stamens and a white, feathery style.

[photo of individual spikelet] At the base of a spikelet are a pair of glumes (bracts). The lower glume is slender, awl-like, 3 to 6 mm long, the upper glume more lance shaped, 6 to 8 mm long, both with stiff hairs on the outer surface. At the base of a floret are a pair of bracts (lemma and palea). The fertile lemma is 5 to 8 mm long, rough-hairy on the keel with a sharp point at the tip, and two lateral nerves that usually extend into short awns, making it 3-lobed. The sterile lemma has one central awn up to about 5 mm long and two shorter lateral awl-like awns.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of sheath, ligule and node] Leaves are crowded on the lower part of the stem with few widely spaced above. Leaves are flat or folded lengthwise, the lower up to 12 inches long and less than ¼ inch wide, rather shorter on the upper stem. Edges and the upper surface are rough, the lower smooth to minutely hairy, sometimes with sparse long hairs on one or both surfaces and/or long spreading hairs scattered around the edge near the base. The sheath is open, forming a long “V” at the front, is variously hairy on the back, sometimes with long, spreading hairs scattered around edges. The ligule (membrane where the leaf joins the sheath) is a band of hairs about .5 mm long. Nodes are hairless and green to purplish. The culm (stem) is hairless and erect to ascending, sometimes arching at the tip end. Stems are solitary or in small clumps and create loose colonies through long rhizomes. Stems take on a tan color in fall and persist through winter.

Fruit: Fruit type: seed without plume

[scan of mature spikes] Spikelets turn tan with age, the entire spike eventually falling off leaving a naked stem behind.

[photo of dissected mature spikelet] The grain (seed) is golden brown, oblong-elliptic, about 3 mm long and 1 mm wide.

Notes:

Side-oats Grama is a dry to mesic prairie species, common throughout both tall and short grass regions. Similar in height to Little Bluestem (Schizachyrium scoparium), it does not approach tall grass species though is much taller generally than very short dry prairie species. It is easily recognizable at a glance by the arching row of short, drooping spikes, which often appear to be arranged on only one side of the stem though on closer inspection you'll see they are not. Tolerant of a range of sites, Side-oats Grama responds well in restorations and native gardens, perhaps too aggressively in a small, urban, native landscape. It has performed very well for me in an isolated boulevard planting, greatly reducing the discharge of nutrients from my lawn into the storm sewer system. There are 3 recognized varieties: var. caespitosa is strongly clump-forming with short knotty rhizomes; var. tenuis has stolons (above ground horizontal stems); var. curtipendula is long-rhizomanous, not strongly clump-forming, is the most common and is the species found in Minnesota, where the other two are limited to the southwestern US.

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More photos

Photos by K. Chayka taken at Glacial Lakes State Park, Pope County and in her garden in Ramsey County. Photos courtesy Peter M. Dziuk taken in Ramsey and Winona counties.

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