8. Cyperus esculentus L. (yellow nutgrass)
Pl. 68 a; Map 252
C. esculentus var. leptostachyus
Boeck.
C. esculentus var. macrostachyus
Boeck.
C. esculentus f. angustispicatus
(Britton) Fernald
Plants perennial, with slender rhizomes
with small tubers at the tips. Aerial stems 10–70 cm long, sharply trigonous, the
sides usually somewhat concave, smooth. Leaf blades 5–45 cm long, 3–10 mm wide
(sometimes folded longitudinally and thus appearing narrower), shorter than to
longer than the stems. Inflorescences irregularly compound umbels often with 1
to several sessile spikes and usually with 2–10 primary rays, each ray smooth,
usually branched again near the tip, the short branches ending in a spike.
Inflorescence bracts 3–8, mostly longer than the rays, spreading to ascending,
often arched outward or downward. Spikes 15–30 mm long, with 8–50 spikelets,
broadly oblong-ovate in outline, usually not dense, often appearing somewhat
flattened, the spikelets mostly spreading at right angles to the axis, attached
more or less alternately on the axis, the spikelet bases readily visible.
Spikelets 5–30 mm long, linear to narrowly elliptic, pointed at the tip,
circular to somewhat 4-angled in cross-section, with 8–35 florets, the fruits
and scales shed successively from the base to the tip, leaving the persistent
axis. Spikelet axis winged. Spikelet scales 2.0–3.0(–3.5) mm long, strongly
overlapping, appressed or ascending, oblong-elliptic to ovate, more or less
rounded along the back, bluntly pointed at the tip, the midrib sometimes
extended into a short point, straight, with 7–9 nerves, yellowish brown to
brown, the margins sometimes with a lighter, narrow band, the midrib green.
Stamens 3, the anthers 1.3–1.8 mm long. Stigmas 3. Fruits 1.3–2.0 mm long,
oblong-obovate in outline, unequally 3-angled in cross-section (2 sides flat,
the other somewhat rounded), the surface finely pebbled, yellowish brown to
brown, shiny. 2n=108, 208. June–October.
Common throughout Missouri (nearly
worldwide, especially in tropical and warm-temperate regions). Moist
depressions of upland prairies, openings of mesic upland forests, and margins
of streams, rivers, ponds, and lakes; also pastures, fallow fields, crop
fields, roadsides, railroads, and moist, open areas.
This species is quite variable in
inflorescence, spikelet, and floret features. Several authors have attempted to
subdivide it into varying numbers of infraspecific taxa. Most recently,
Schippers et al. (1995) recognized four varieties in their confusing study of
quantitative variation in spikelet and inflorescence morphology within the
species. In their key, most Missouri specimens seem to come closest to var. leptostachyus,
with only a few collections representing var. esculentus and var. macrostachyus
from the state. However, none of the characters cited by Schippers et al.
appear to resolve the Missouri specimens into discrete taxa, and an
infraspecific classification for C. esculentus seems unwarranted.
Plants of C. esculentus often have a
sweet aroma when bruised or during drying.