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fork fimbry

annual fimbry

Habit Plants perennial, cespitose, (10–) 20–80 cm, base thickened, not bulbous; rhizomes absent. Plants annual, cespitose, 5–50 cm, base 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.

nearly distichous, 1/2 to equal length of culms;

sheaths bristlyciliate apically, backs glabrous or hirtellous;

ligule present, complete;

blades narrowly linear, 1–1.5(–2) mm wide, flat to shallowly involute, margins ciliate-scabrid, adaxial and abaxial surfaces glabrous or pubescent.

Inflorescences

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

scapes slender, 1 mm wide, slightly compressed distally;

proximalmost involucral bract exceeding anthela.

anthelae simple or compound, mostly open, diffuse, ascending-branched, longer than broad;

scapes slender, 1 mm thick, angular;

proximalmost involucral bract longer or shorter than anthela.

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.

tan to brown or redbrown, ovoid to lance-ovoid, 3–8 mm;

fertile scales broadly oblong to ovate, 2 mm, acute to obtuse-angled, smooth, midrib reaching apex or excurrent as mucro.

Flowers

stamens 1–2;

styles 2-fid, flat, fimbriate.

stamens 1(–2);

styles 2-fid, flat, fimbriate.

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.

white to brown, often iridescent, lenticular or obovoid to pyriform-obovoid, 1 mm, cancellate, with 5–12 longitudinal ribs per side, alternating with as many rows of horizontally rectangular pits;

warts of achene more usually distributed, or achene (rarely) smooth.

2n

= 20, 30.

= 30.

Fimbristylis dichotoma

Fimbristylis annua

Phenology Fruiting summer–fall, into winter southward. Fruiting summer–fall, all year southward.
Habitat Moist, usually sandy waste areas, roadsides, low fields, and savannas Various moist to wet substrates, often on exposed, recently disturbed soils around or in shallow temporary pools in outcrops, in savannas, fields, and paddies
Elevation 0–200 m (to 2000 m, tropics) (0–700 ft (to 6600 ft, tropics)) 0–1000 m (0–3300 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; DC; DE; FL; GA; IL; IN; KS; KY; LA; MD; MI; MO; MS; NC; NJ; NY; OH; OK; PA; SC; TN; TX; VA; Mexico; Central America; South America; Atlantic Islands; Pacific Islands; Indian Ocean Islands; West Indies; Africa; Eurasia; Bermuda; Australia
[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.)

The extensive, yet incomplete, synonymy above partly illustrates the polymorphic nature of Fimbristylis annua, there being many “stabilized” morphs in specialized habitats and much exchange of achenes mixed with grass seeds (particularly rice).

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

Source FNA vol. 23, p. 125. FNA vol. 23, p. 126.
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. 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, F. vahlii
Synonyms Scirpus dichotomus, F. annua var. diphylla, F. brizoides, F. diphylla subsp. diffusa, F. glauca, F. polymorpha, Scirpus diphyllus Scirpus annuus, F. alamosana, F. arenicola, F. baldwiniana, F. darlingtoniana, F. diphylla var. tomentosa, F. hirtella, F. holwayana, F. serratula, F. verrucosa, Scirpus baldwinianus, Scirpus depauperatus, Scirpus elliottii, Scirpus sulcatus
Name authority (Linnaeus) Vahl: Enum. Pl. 2: 287. (1805) (Allioni) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 95. (1817)
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