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fork fimbry

southern fimbry

Habit Plants perennial, cespitose, (10–) 20–80 cm, base thickened, not bulbous; rhizomes absent. Plants annual, cespitose, to 30 cm, base soft, not bulbous; 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, mostly spreading, to 2/3 length of culms;

sheaths ciliate, sheath backs often pilose-hirsute;

ligule present, complete;

blades narrowly linear, 1.5–2.5 mm wide, flat or shallowly concave, margins scabrid, abaxial surface scattered-pilose, hirsute-ciliate at least proximally.

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, open, divaricately branched, mostly as broad as long;

scapes slender, 1 mm wide, distally slightly compressed;

proximalmost involucral bract exceeding 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.

pale brown or red-brown, ovoid to lanceoloid, 5–6 mm;

fertile scales broadly ovate, 1.5–2 mm, acute- to obtuse-angled, midrib short-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.

whitened-iridescent to brown, lenticular or pyriform-obovoid, 1 mm, cancellate, each face with 5–12 vertical rows of transversely oriented rectangular pits, achene margins distally papillose.

2n

= 20, 30.

= 20.

Fimbristylis dichotoma

Fimbristylis decipiens

Phenology Fruiting summer–fall, into winter southward. Fruiting late summer–fall.
Habitat Moist, usually sandy waste areas, roadsides, low fields, and savannas Disturbed sites, low pinelands, banks, and fields
Elevation 0–200 m (to 2000 m, tropics) (0–700 ft (to 6600 ft, tropics)) 0–100 m (0–300 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; FL; GA; LA; MS; NC; SC; TX
[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.)

In the Atlantic and Gulf Coastal plains, Fimbristylis decipiens often shares habitat with two close, likewise weedy, relatives: F. dichotoma and F. annua. From the former F. decipiens is distinguished by its annual habit, its papillose distal achene edges, and the more spreading anthela branches; from the latter it differs in its usually less papillose achene and its harder, more spreading foliage. No intergrades appear to occur among the three.

(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. annua, F. autumnalis, F. brevivaginata, F. caroliniana, F. castanea, F. cymosa, 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
Name authority (Linnaeus) Vahl: Enum. Pl. 2: 287. (1805) Kral: Sida 4: 119, fig. 38. (1971)
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