104. Carex tristachya Thunberg in Murray, Syst. Veg., ed. 14. 845. 1784.
三穗薹草 san sui tai cao
Rhizome short. Culms tufted, 20-45 cm tall, slender, obtusely trigonous, smooth. Basal sheath dark brown, split into fibers. Leaves shorter than or nearly equaling culm, blades 2-4(-5) mm wide, flat, margins scabrid. Involucral bracts leaflike, longer than subtending spikes, sheathed, sheath 6-12 mm. Spikes 4-6, upper ones contiguous and fastigiate, sometimes lowest one distant; terminal spike male, linear-cylindric, 10-40 × 1-1.5 mm, subsessile, male glumes free or connate from base to above middle, filament of stamen threadlike or flat, free or connate; lateral spikes cylindric, 10-30(-35) × 2-3 mm, densely flowered; upper peduncles short and enclosed in involucral bract sheath, lowest one exserted. 2.5-3.5(-5.5) cm, erect, slender. Female glumes pale yellow laterally, elliptic or oblong, ca. 2 mm, costa green, apex obtuse, truncate, or acute, mucronate. Utricles green, longer than glume, erect, ovate-fusiform, trigonous, 3-3.2 mm, membranous, puberulent, many veined, base attenuate and stipitate, apex attenuate into a beak, orifice minutely 2-toothed. Nutlet pale brown, tightly enveloped, ovate, 2-2.5 mm, apex discoid-annulate; style base conically thickened; stigmas 3. Fl. and fr. Mar-May.
Waysides and grasslands on mountain slopes, wet places in forests and field margins, forests; 300-1100 m. Anhui, Fujian, Guangdong, Guangxi, Hainan, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Zhejiang [Japan, Korea].