big bluestem (beardgrass, blue joint, turkey foot)
Andropogon gerardii Vitman

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habithabitinflorescenceinflorescencespikeletdrawing

Big bluestem is widely distributed in North America, from the Atlantic coast to the Rocky Mountains and from Florida and New Mexico to the prairie provinces of Canada.
Big bluestem was a dominant species in the tall grass prairie that covered much of Iowa before European settlement. It can still be seen in a few remaining patches of original prairie as well as in many roadside plantings and prairie restorations. Big bluestem is aptly named as the stems can reach heights of up to 10 feet and take on a bluish tint as they dry out in the fall. Turkey foot, another common name for the species, refers to the appearance of the flowering heads, which often have three finger-like branches (rames). Big bluestem produces a large amount of high quality forage and is valued as a mid- and late-summer forage. The use of big bluestem and other native warm season grasses as pasture crops is becoming increasingly popular as these grasses are most productive later in the season, a time when introduced pasture grasses such as brome and bluegrass are dormant and unproductive. Big bluestem prefers slightly moist sites and is most common on moist lower slopes, but it can grow in drier soils as well.

Sand bluestem (Andropogon hallii) is very similar to big bluestem, and can hybridize with it. The two species are distinguished by the presence of more prominent rhizomes, grayer, waxier-appearing leaves, and very hairy joints in the flowering heads of sand bluestem. Big bluestem is also less drought tolerant than sand bluestem.

Etymology: Andropogon from the Greek andros = man and pogon = beard, as the hairy spikelets characteristic of this genus are said to resemble a man’s beard; the specific epithet gerardii is given in honor of Louis Gerard (1733-1819), a French physician and botanist.

 

Plants perennial, stout, lacking rhizomes or with short-scaly rhizomes. Culms 85-170 cm tall, solid, grooved on one side, usually with a waxy bloom. Leaves with the sheaths open, only slightly keeled, smooth; ligules fringed membranes 1.5-3 mm long; blades 21-50 cm long, 4-8 mm wide, mostly smooth but often with a few long hairs on the upper surface near the base of the blade. Flowering heads 7-14 cm long, 1.5-3 (-8) cm wide, of 2-5 (-7) rames at or near the tip of the stem, occasionally with some smaller inflorescences from the axils of the leaves. Rames 5-12 cm long, exserted at maturity, usually purple/bluish, occasionally yellowish; joints pubescent, hairs white or sometimes yellow, 1-2.5 mm long, often relatively sparse. Sessile spikelets 6.8-10 mm long, glumes more or less equal, scabrous; awns 7-15 mm long, twisted at the base and bent once. Pedicillate spikelets usually developed and staminate, occasionally sterile, often as long as the sessile spikelets. Chromosome number 2n usually = 60 but can be 20, 40, 70 or 80.

 

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