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fork fimbry

Vahl's fimbristylis, Vahl's fimbry

Habit Plants perennial, cespitose, (10–) 20–80 cm, base thickened, not bulbous; rhizomes absent. Plants annual, cespitose, delicate, 4–15 cm, bases soft; rhizomes absent.
Leaves

nearly distichous, spreading to ascending, 1/2 length of culms;

sheaths distally ciliate, backs mostly glabrous;

ligule line of short hairs;

blades narrowly linear, 2–3 mm wide, flat to broadly involute, scabridciliate, adaxially smooth or hirtellous.

polystichous, mostly spreading or excurved, often exceeding culms;

sheaths entire, abaxially smooth or sparsely hirtellous;

ligule absent;

blades filiform, to 0.5 mm wide, somewhat involute, abaxially glabrous or ascending-strigillose.

Inflorescences

anthelae compound, dense or open, ascending-branched, longer than broad;

scapes slender, 1 mm wide, slightly compressed distally;

proximalmost involucral bract exceeding anthela.

terminal;

spikelets sessile or subsessile in single capitate leafy-involucrate cluster;

scapes filiform;

involucral bracts leafy, setaceous, greatly overtopping inflorescence.

Spikelets

pale drab brown to chestnut brown, ovoid-lanceoloid, 4–8 mm;

fertile scales broadly oblong or ovate, 2 mm, acute to obtuse angled, glabrous, midrib reaching scale tip or excurrent, finely mucronate.

greenish, cylindric to lanceoloid-cylindric, 5–10 mm;

fertile scales narrowly ovate to lanceolate, 1–1.5 mm, acute, glabrous, midrib strong, excurrent as cusp.

Flowers

stamens 1–2;

styles 2-fid, flat, fimbriate.

stamens 1;

styles 2-fid, slender, bulbous-based, smooth or papillate.

Achenes

white to brownish, lenticular, obovoid, 1–1.2 mm, cancellate, each face longitudinally with (5–)10–12 ribs, connected by vertical rows of horizontally rectangular pits.

pale, tumidly obovoid, 0.5–0.7 mm, cancellate, pits horizontally rectangular in 5–7 vertical rows per side.

2n

= 20, 30.

= 20.

Fimbristylis dichotoma

Fimbristylis vahlii

Phenology Fruiting summer–fall, into winter southward. Fruiting summer–fall.
Habitat Moist, usually sandy waste areas, roadsides, low fields, and savannas Moist to wet, alluvial or mineralized banks, shores, fluctuating pond and lake edges, often a “drawdown” plant around stock tanks and reservoirs
Elevation 0–200 m (to 2000 m, tropics) (0–700 ft (to 6600 ft, tropics)) 0–500 m (0–1600 ft)
Distribution
from FNA
AL; FL; GA; LA; MS; NC; SC; TX; Mexico; Central America; South America; Atlantic Islands; Pacific Islands; Indian Ocean Islands; West Indies; Africa; Eurasia; Bermuda; Australia [Introduced in North America]
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; AZ; CA; FL; GA; IL; KS; KY; LA; MO; MS; NE; OK; SC; TN; TX; Mexico; Central America; South America
[WildflowerSearch map]
[BONAP county map]
Discussion

Fimbristylis dichotoma is found in temperate to tropical regions worldwide. It is one of the most widespread and weedy species of Fimbristylis, unquestionably with many races and forms. The two commonest forms in the United States often occur in mixed populations, one sort with inflorescence branches more ascending, inflorescence dense, habit lower, and leaves broader; the other sort usually taller, inflorescence more sparse, branches more widely spreading, and leaves more ascending and narrower. The abundance of such plants both in regions where rice originated and in regions where rice is, or was, introduced, indicates an Asian origin for such weeds.

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

Source FNA vol. 23, p. 125. FNA vol. 23, p. 127.
Parent taxa Cyperaceae > Fimbristylis Cyperaceae > Fimbristylis
Sibling taxa
F. annua, F. autumnalis, F. brevivaginata, F. caroliniana, F. castanea, F. cymosa, F. decipiens, F. miliacea, F. perpusilla, F. puberula, F. schoenoides, F. squarrosa, F. thermalis, F. tomentosa, F. vahlii
F. annua, F. autumnalis, F. brevivaginata, F. caroliniana, F. castanea, F. cymosa, F. decipiens, F. dichotoma, F. miliacea, F. perpusilla, F. puberula, F. schoenoides, F. squarrosa, F. thermalis, F. tomentosa
Synonyms Scirpus dichotomus, F. annua var. diphylla, F. brizoides, F. diphylla subsp. diffusa, F. glauca, F. polymorpha, Scirpus diphyllus Scirpus vahlii, F. apus, F. congesta, F. vincentii, Isolepis vahlii, Scirpus apus
Name authority (Linnaeus) Vahl: Enum. Pl. 2: 287. (1805) (Lamarck) Link: Hort. Berol. 1: 287. (1827)
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