Flower:

Open, airy, heavily branched cluster generally taller than wide when fully expanded, 5 to 20 inches tall and 3 to 9 inches wide with profuse, wiry, widely-spreading branches. Branches diverge multiple times off the central stalk (rachis), green turning reddish purple with maturity, rough-textured with clusters of short, straight hairs in the axils, and a spikelet (flower cluster) at the tip of each branchlet. The base of the cluster is typically enclosed by the uppermost leaf sheath.

Spikelets are lance-elliptic, widest near the middle, 2 to 4 mm long, 1.5 to 2 mm wide, hairless with 1 sterile (lower) and 1 fertile (upper) floret, and a pair of bracts (glumes) at the base. Glumes are lance-elliptic, the upper glume 2 to 3 mm long and 7 to 9 veined, the lower glume 1/3 to ½ the length of the upper. Florets are each surrounded by a pair of bracts (lemma and palea) though the sterile palea is often absent. The sterile lemma is opposite the upper glume on the spikelet and about the same length, extending just above the fertile floret, hiding it, and is prominently veined. The fertile floret is smaller, slightly flattened, and usually straw-colored at maturity, sometimes turning blackish.

Leaves and stems:

Leaves are mostly along the stem, becoming larger above, up to 15 inches long, ½ to nearly ¾ inch wide, often drooping and wavy along the edges like corn leaves. Plants are hairy throughout, the hairs usually from a swollen pimple-like base (papillose). Leaves are sparsely to moderately hairy on both surfaces, sometimes hairless on the upper surface and only hairy along the midvein on the underside.

The sheath is densely hairy, the edges overlapping near the tip. The ligule (membrane where the leaf joins the sheath) is membranous with short hairs about 1 mm long along the edge. Nodes are densely hairy and green to purplish. Stems are leafy, multiple from the base, branching from the base as well as the upper stem, erect or sprawling from the base but rising at a node, often very stout, with fibrous annual roots.

Fruit:

The entire cluster breaks off at maturity, blowing to new locations tumbleweed fashion. Spikelets are often dark purple at maturity. The fertile floret encasing the grain (seed) typically falls away early, leaving the glumes and sterile lemma temporarily persisting on the stalk, but they, too, eventually drop off. The grains are shiny, egg-shaped to oblong-elliptic, 1.5 to 2 mm long and 1/3 to 2/3 as wide.

Notes:

Witchgrass is a common weedy native species throughout all of Minnesota and indeed throughout much of North America. The few counties in our map that indicate its absence is likely a matter of no one having collected it yet. It shows up just about any place the soil has been disturbed including road ditches, field margins, empty lots, and your back yard garden. It is similar to two other tumblegrass species in Minnesota, Fall Witch Grass (Digitaria cognata) and Purple Lovegrass (Eragrostis spectabilis), both of which are perennial and have hairless stem nodes, where Witchgrass is annual with densely hairy nodes. While D. cognata also has a single fertile floret in a spikelet, it is further distinguished by the lower glume reduced to a tiny scale, leaves narrower and stiffer, and the whole plant much less to mostly hairless throughout. E. spectabilis spikelets have 4 or more florets, stems are unbranched, the ligule a band of long hairs, and is also less hairy overall except for the lower sheaths. There are 2 recognized subspecies of Panicum capillare: subsp. hillmanii (a.k.a. Panicum hillmanii) is often blue-green rather than purple, has more appressed cluster branches, usually blackish fertile florets, and has a limited range in the southern Great Plains with adventive populations in California; subsp. capillare is the more common, described above, and is found in Minnesota.