Plants perennial; cespitose. Culms 9-75 cm, erect or decumbent. Ligules 2-6.5 mm, obtuse, puberulent dorsally; blades 2-10 cm long, 1-5(8) mm wide; upper sheaths not inflated. Panicles 1-9 cm long, 3-9 mm wide. Glumes 1.8-3.7 mm, connate near the base, membranous, pubescent on the sides, keels not winged, ciliate, apices obtuse, sometimes erose, pale green, occasionally purplish; lemmas 1.5-2.5(3.5) mm, connate in the lower 1/3-1/2, glabrous, apices obtuse, awns 0.7-3 mm, straight, exceeding the lemmas by 0-2.5 mm; anthers 0.5-1.2 mm, usually pale to deep yellow or orange, rarely purple. Caryopses 1-1.8 mm. 2n = 14, 28.
Alopecurus aequalis is native to temperate zones of the Northern Hemisphere. It generally grows in wet meadows, forest openings, shores, springs, and along streams, as well as in ditches, along roadsides, and in other disturbed sites, from sea level to subalpine elevations.
Alopecurus aequalis is the most widespread and variable species of Alopecurus in the Flora region. Despite its variability, only the phenotype found in the low marshes of Marin and Sonoma counties, California merits formal recognition. Some high elevation plants of the Sierra Nevada have unusually long awns (exserted by up to 1.5 mm) and anthocyanic spikelets but, like the semi-aquatic ecotype A. aequalis var. natans (Wahlenb.) Fernald, they do not warrant taxonomic recognition.
Alopecurus haussknechtianus Asch. & Graebn. is a hybrid between A. aequalis and A. geniculatus, which occurs fairly frequently in areas of sympatry, particularly in drier midcontinental areas in Alberta to Saskatchewan, south to Arizona and New Mexico. The hybrids apparently have 2n = 14; they are sterile.