Flower:

Flowering cluster 2 to 12 inches long, initially erect soon becoming arching, with 4 to 33 spikelets (flower clusters), 1 to a few spikelets on each erect to ascending branch. Spikelets are ¼ to 2/3 inch (7 to 17 mm) long with 3 to 5 fertile florets and a sterile floret at the tip.

At the base of a spikelet is a pair of bracts (glumes) that are green to straw-colored, lance-elliptic, pointed at the tip, the lower glume 1.7 to 3.7 mm long 3 to 6 mm long and 1 to 3-veined, the upper glume 2.2 to 5.2 mm long and 3 to 5-veined. Surrounding a floret is a pair of bracts (lemma and palea), the lemma broadly elliptic to urn-shaped, 3.7 to 7.5 mm long, 3-veined, the midvein with a short extension to a pointed tip; the palea is a little more than half as long as the lemma, notched at the tip and 2-veined. The sterile floret is similar to the fertile but underdeveloped.

Leaves and stems:

Leaves are mostly near the base, 9 to 28 inches long, 6 to 18 mm wide (to ~¾ inch) wide, the upper surface hairless to sparsely hairy, the lower surface hairless but rough-textured. Blades are flat, arching, quite shiny especially when young, and the midvein is often noticeably off-center.

The sheath is hairless, sometimes sparsely short-hairy along the edges. The ligule (membrane where the leaf joins the sheath) is .2 to 1 mm long, minutely fringed across the top. Nodes are smooth, often hidden by the sheaths. Stems are hairless, unbranched, usually multiple from the base forming dense clumps, sometimes single, and may form colonies from long rhizomes.

Fruit:

Spikelets turn light brown brown to straw-colored at maturity, the florets shedding as each grain matures, the glumes left behind and persisting on the stalk. Grains are tan to light golden brown, 4.1 to 6 mm long, elliptic to somewhat urn shaped with an abrupt taper to a stout beak; they are quite plump, spreading the lemma and palea apart as they mature.

Notes:

Obovate Beakgrass, formerly Diarrhena americana var. obovata, is an occasional to common, floodplain or upland forest grass in the central part of its range, but reaches the northern-most edge of that range in Minnesota. According to the DNR, it was unknown in the state until 1994 when a single population was found along the Root River in Fillmore County. It was subsequently listed as a Special Concern species in 1996, then elevated to Endangered in 2013 after biological surveys of suitable habit found no additional populations. Its habitat is most at risk from invasive species, such as Buckthorn and Garlic Mustard, but also from forest clearing, livestock grazing and potentially development.

It's very unique for a grass and should not be confused with any other species—the bottle-shaped grains are unlike those of other grasses. Even when flowering stems are not present, it can be recognized by the typically large clumps of glossy, slightly hairy, arching leaves with off-center midveins. It's eye-catching, so much so that we unexpectedly stumbled upon a new population while searching for ferns in Forestville Mystery Cave State Park. We didn't realize the significance of this at the time but are now following-up with the DNR's Biological Survey team about this find.