Flower:

2 to 6 slender, finger-like spikes clustered at the top of the stem and at the tips of any branches in the upper plant. Spikes are 2 to 4 inches long and mostly ascending, usually purplish, sometimes yellowish.

Spikelets (flower clusters) are in pairs all along the spike; 1 stalkless, awned spikelet containing a single fertile, perfect flower (both male and female parts) and usually 1 stalked spikelet containing a single male flower, or sometimes 1 sterile spikelet with no flower, just the stalk. The glumes (pair of bracts at the base of a spikelet) are about 3/8 inch long and equal in length, narrowly lance-elliptic with a sharply pointed tip. The lemma (bract at the base of a flower) of the fertile flower has a ½ to ¾-inch long awn that is twisted and bent near its base. Spikelet stalks are usually densely covered in fine hairs that are initially appressed but spread out as the spikelets mature.

Leaves and stems:

Leaves are mostly crowded on the lower stem with few in the upper plant. Leaves are mostly flat, green to blue-green, up to 18 inches long and to ½ inch wide, becoming shorter as they ascend the stem. The upper surface is rough textured, often with long, white, spreading hairs near the base.

The sheath is open, forming a distinct “V” at the front. The ligule (membrane where the leaf joins the sheath) is white to brownish and up to 2.5 mm long. Nodes are hairless and purplish. The culm (stem) is erect, hairless, few branched and often bluish to purple with a waxy bloom. Plants can create large clumps from short rhizomes.

Fruit:

The spikelets spread out some as they mature, the hairs on the stalks spreading as well, the entire spikelet eventually dropping off. The seed that develops in the fertile spikelet is golden brown, narrowly elliptical, and nearly as long as the spikelet.

Notes:

Big Bluestem is one of the iconic prairie grasses that once covered a large portion of Minnesota. It's easy to ID from the finger-like array of spikes at the tips of the tall stems.