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Asian flatsedge, smallflower umbrella sedge, variable flatsedge

nut flatsedge, nut grass, yellow nut sedge, yellow nut-grass

Habit Herbs, annual, cespitose. Herbs, perennial, stoloniferous; stolons soft, spongy, flexible when dried, 2–8(–15) cm, bearing tubers (3–)6–11 mm diam.
Culms

1–15, trigonous, 7–30 cm × 1.2–2.5 mm, soft (flattened in pressing), glabrous.

trigonous, 15–60 (–100) cm × 0.6–3.4 mm, glabrous.

Leaves

2–7, flat, (2–)7–22 cm × 2.2–4 mm.

3–7, flat to V-shaped or flanged V-shaped, (6–)20–40(–80) cm × 2–4 (–6.5) mm.

Inflorescences

heads dense, 7–17 mm diam.; when rays short, heads sessile or nearly so, then densely irregularly lobate, 12–35 mm diam.;

rays 1–5, 2–32 mm;

bracts 2–4, longest bract erect or nearly so, appearing as continuation of culm, other bracts horizontal to ascending, 1–22 cm × 0.5–3.5 mm, margins and keel minutely scabridulous.

spikes broadly ellipsoid to ovoid or hemispheric, (12–)18–30 × (12–)18–35 mm;

rachis 4–17 mm;

rays 4–10, (0.3–)2–12 cm;

bracts (3–)4–5(–7), ± horizontal to ascending at 45(–75)°, V-shaped to flanged V-shaped, (1.5–)5–30 cm × 0.5–4 mm;

rachilla persistent, wings hyaline, 0.3–0.5 mm wide.

Spikelets

30–120, greenish brown to purplish brown, oblong-ellipsoid, compressed, (2–)3–5(–6) × 0.8–1.2 mm;

floral scales (6–)12–20(–30), laterally clear margins, stramineous to deep purple, medially greenish, stramineous, or purplish, laterally ribless, medially 3-ribbed, obovate to orbiculate, 0.6–0.8 × 0.6–0.8 mm, apex mucronulate.

(3–)10–20(–28), divaricate or ascending, yellowish brown to dark brown, linear to linear-lanceoloid, compressed-quadrangular, (5–)10–20(–55) × (1.2–)1.4–2(–3) mm;

floral scales persistent, 6–34, spreading or appressed, ovate-lanceolate, laterally 7–9-ribbed, laterally yellowish brown to dark brown medially brownish, reddish, or greenish, ovate, or ovate-deltate, medially 3-ribbed, 1.8–2.7(–3.4) × (1–)1.5–1.8(–2.4) mm, apex acute or subacute.

Flowers

stamens 1 or 2;

anthers ovoid-ellipsoid, 0.1 mm, connective not prolonged;

styles 0.1 mm;

stigmas 0.1–0.3 mm.

anthers (1–)1.2–1.5(–2.1) mm;

styles (0.7–)1–1.2(–2.2) mm;

stigmas (1.2–)1.8–2.3(–4) mm.

Achenes

light brown, obovoid-ellipsoid, 0.6–0.8 × 0.3–0.4 mm (as long as subtending scale), base cuneate, apex obtuse, apiculate, surfaces finely reticulate, papillose.

(seldom maturing) brown, sessile, ellipsoid, (1.1–)1.3–1.5(–1.6) × 0.3–0.6(–0.8) mm, apex obtuse, surfaces puncticulate.

Cyperus difformis

Cyperus esculentus

Phenology Fruiting summer.
Habitat Disturbed, muddy soils, shallow waters
Elevation 0–1000 m (0–3300 ft)
Distribution
from FNA
AL; AZ; CA; FL; GA; ID; KY; LA; MS; NC; NJ; NM; OR; PA; SC; TN; TX; VA; Mexico; South America; West Indies (Puerto Rico); Central America (Nicaragua, Panama); Eurasia; Indian Ocean Islands; Pacific Islands; Australia [Introduced in North America]
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; BC; NB; ON; QC; nearly worldwide
[WildflowerSearch map]
[BONAP county map]
Discussion

Cyperus difformis is naturalized in the New World and native to the Old World, where it ranges from southern Europe to southern Africa and eastward to Southeast Asia and Australia.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Varieties 4 (3 in the flora).

Cyperus esculentus is a widespread and polymorphic species. Although seven varieties have been recognized (G. Kükenthal (1935–1936), recent studies based primarily on spikelet features provided support for four varieties (P. Schippers et al. 1995). Cyperus esculentus var. esculentus is restricted to the Old World.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Spikelets ascending-erect; floral scales deltate-ovate, widest ca. 1/4–1/3 of length.
var. heermannii
1. Spikelets divaricate; floral scales ovate to ovate-lanceolate, widest at midlength.
→ 2
2. Spikelets (1.2–)1.5–2 mm wide; floral scales 1.8–2.7 mm; anthers (1–)1.3(–1.6) mm; styles (0.7–)1–1.2 mm; stigmas (1.2–)1.8(–2.5) mm.
var. leptostachyus
2. Spikelets 2.4–3 mm wide; floral scales (2.7–) 2.9–3.4(–3.6)mm; anthers (1.2–)1.3–2(–2.1) mm; styles (0.9–)1.3–2(–2.2) mm; stigmas (2–) 2.3–2.8(–4) mm.
var. macrostachyus
Source FNA vol. 23, p. 156. FNA vol. 23.
Parent taxa Cyperaceae > Cyperus > subg. Pycnostachys Cyperaceae > Cyperus > subg. Cyperus
Sibling taxa
C. acuminatus, C. aggregatus, C. alopecuroides, C. amabilis, C. articulatus, C. bipartitus, C. cephalanthus, C. compressus, C. croceus, C. cuspidatus, C. dentatus, C. dentoniae, C. diandrus, C. digitatus, C. dipsaceus, C. distans, C. distinctus, C. drummondii, C. echinatus, C. elegans, C. entrerianus, C. eragrostis, C. erythrorhizos, C. esculentus, C. fendlerianus, C. filicinus, C. filiculmis, C. filiformis, C. flavescens, C. flavicomus, C. floribundus, C. fugax, C. fuligineus, C. fuscus, C. giganteus, C. gracilis, C. granitophilus, C. grayi, C. grayoides, C. haspan, C. hermaphroditus, C. houghtonii, C. hypopitys, C. hystricinus, C. involucratus, C. iria, C. laevigatus, C. lancastriensis, C. lanceolatus, C. lecontei, C. lentiginosus, C. ligularis, C. lupulinus, C. manimae, C. microiria, C. mutisii, C. niger, C. ochraceus, C. odoratus, C. onerosus, C. ovatus, C. owanii, C. oxylepis, C. pallidicolor, C. papyrus, C. parishii, C. pilosus, C. planifolius, C. plukenetii, C. polystachyos, C. prolifer, C. prolixus, C. pseudothyrsiflorus, C. pseudovegetus, C. pumilus, C. reflexus, C. refractus, C. retroflexus, C. retrofractus, C. retrorsus, C. rotundus, C. sanguinolentus, C. schweinitzii, C. serotinus, C. seslerioides, C. setigerus, C. spectabilis, C. sphacelatus, C. sphaerolepis, C. squarrosus, C. strigosus, C. surinamensis, C. tetragonus, C. thyrsiflorus, C. virens
C. acuminatus, C. aggregatus, C. alopecuroides, C. amabilis, C. articulatus, C. bipartitus, C. cephalanthus, C. compressus, C. croceus, C. cuspidatus, C. dentatus, C. dentoniae, C. diandrus, C. difformis, C. digitatus, C. dipsaceus, C. distans, C. distinctus, C. drummondii, C. echinatus, C. elegans, C. entrerianus, C. eragrostis, C. erythrorhizos, C. fendlerianus, C. filicinus, C. filiculmis, C. filiformis, C. flavescens, C. flavicomus, C. floribundus, C. fugax, C. fuligineus, C. fuscus, C. giganteus, C. gracilis, C. granitophilus, C. grayi, C. grayoides, C. haspan, C. hermaphroditus, C. houghtonii, C. hypopitys, C. hystricinus, C. involucratus, C. iria, C. laevigatus, C. lancastriensis, C. lanceolatus, C. lecontei, C. lentiginosus, C. ligularis, C. lupulinus, C. manimae, C. microiria, C. mutisii, C. niger, C. ochraceus, C. odoratus, C. onerosus, C. ovatus, C. owanii, C. oxylepis, C. pallidicolor, C. papyrus, C. parishii, C. pilosus, C. planifolius, C. plukenetii, C. polystachyos, C. prolifer, C. prolixus, C. pseudothyrsiflorus, C. pseudovegetus, C. pumilus, C. reflexus, C. refractus, C. retroflexus, C. retrofractus, C. retrorsus, C. rotundus, C. sanguinolentus, C. schweinitzii, C. serotinus, C. seslerioides, C. setigerus, C. spectabilis, C. sphacelatus, C. sphaerolepis, C. squarrosus, C. strigosus, C. surinamensis, C. tetragonus, C. thyrsiflorus, C. virens
Subordinate taxa
C. esculentus var. heermannii, C. esculentus var. leptostachyus, C. esculentus var. macrostachyus
Synonyms C. lateriflorus
Name authority Linnaeus: Cent. Pl. II, 6. (1756) Linnaeus: Sp. Pl. 1: 45. (1753)
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