Flower:

A single tightly packed, narrowly cylindric, spike-like branching cluster at the top of the stem, ½ to 3½ inches long. Spikelets (flower clusters) are 1.7 to 3.7 mm (to ~1/8 inch) long, flattened, oblong-elliptic in outline and have a single floret, light to medium green at flowering time. Florets bloom from the top of the spike down, those at the tip of the spike may be forming fruit while those at the base have not yet bloomed.

At the base of a spikelet is a pair of bracts (glumes), both similar, fused together near the base, 3-veined, long-haired along the keel and edges, sparsely hairy on the surface, 1.7 to 3.7 mm long, lance-oblong with a blunt tip. Florets are surrounded by a pair of bracts (lemma and palea), the lemma as long as or slightly shorter than the glumes, 5-veined, hairless, and with an awn arising from near the base of the midvein, the awn .5 to 3 mm long, straight and extending beyond the tip of the glumes by less than 1.5 mm; the palea is obscure or absent. Stamen tips (anthers) are about 1 mm long, mostly less than half as long as the spikelet.

Leaves and stems:

Leaves are basal and alternate, erect to ascending, 1 to 6 inches long, 1 to 7 mm (to ~¼ inch) wide, lance-linear, mostly flat. Basal leaves are longest; stem leaves are few and long-sheathing. When submersed, leaves often float on the water's surface. Sheaths are hairless, the lower tightly wrapping the stem and the upper sometimes slightly inflated and looser, and may be blue-green in color. The ligule (membrane where the leaf joins the sheath) is membranous, 3 to 6.5 mm long, triangular in shape but often folded over and appearing more convex at the tip, and is not fringed with hairs. Nodes are smooth, green to orange. Stems are hairless, multiple from the base, erect or prostrate from the base then rising near the tip (decumbent), sometimes rooting at the lower nodes and forming clumps.

Fruit:

Spikelets turn blackish at maturity, the entire spikelet shedding as each grain matures, leaving the naked stalks behind. Grains (seeds) are 1 to 1.8 mm long.

Notes:

Shortawn Foxtail is a cool-season grass typically found in open, wet places that may dry out in summer. It's frequently found in shallow water. While the distribution map indicates it's common, it is not so easily encountered as one might imagine. We visited a number of sites where it was previously collected only to come up empty, mostly because the sites had become overgrown with Reed Canary Grass. But as luck would have it, we stumbled upon a population at a retention pond near home.

There are 4 Alopecurus species known to be in Minnesota; A. aequalis is one of two natives. At a glance they may all look similar—narrowly cylindric spikes usually blooming (and completely shedding seed) from the top down, single-flowered spikelets usually blackish when mature, hairy glumes equal in size and shape, and lemma awns arising from the lower half of the lemma—but the size of the spikelet combined with length of the awn can help determine a correct ID. Shortawn Foxtail has relatively small spikelets (usually less than 3.5 mm long) and straight awns that only extend about 1 mm beyond the tip of the glumes, though they may be obscured by the long hairs on the glumes. When anthers are present, they are less than half as long as a spikelet, not usually more than 1 mm long. Look for floating leaves when plants are in shallow water.

It is very similar to Water Foxtail (Alopecurus geniculatus), which isn't known to be in Minnesota but could be. Water Foxtail spikelets are similar in size, but its awns are somewhat longer, becoming bent at maturity (Shortawn Foxtail awns stay straight), and anthers are mostly 1.5 to 2 mm long, more than half as long as the spikelet. Of the other Alopecurus species in Minnesota, Carolina Foxtail (A. carolinianus) also has small spikelets (max 3 mm) and awns that noticeably extend beyond the glumes, but its awns are conspicuously much longer becoming bent at maturity, and in Minnesota it is almost exclusively found in rock outcrops, mostly in the Minnesota River Valley.

Of special note is the wide disparity of glume sizes, etc. in different references for A. aequalis and A. geniculatus, which was a great source of confusion as to which species we actually found at the local pond. The ultimate decision came down to the anthers—they were decidedly smaller than the spikelets, as mentioned in several references. If anthers are not present the deciding factor(s) are not as straight forward, though the A. geniculatus spike tends to be a bit shorter and fatter than A. aequalis, awns somewhat longer, and bent at maturity. There are multiple varieties/subspecies of A. aequalis but these are poorly documented; var. aequalis is apparently the most common and is present in Minnesota.