Flora of North America species comparison

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Juncus subg. Juncus

Juncus cooperi

Cooper's rush
Habit Herbs, perennial, rhizomatous. Herbs, perennial, robust, tufted, 4–10 dm.
Rhizomes

short.
Culms

terete, 1.5–2.5 mm diam.
Stems

terete.

Cataphylls

several, reddish brown, often apiculate.
Leaves

basal;

blade terete, not septate.

basal, 1–2;

auricles essentially absent;

blade terete, 10–40 dcm, shorter than culm.
Inflorescences

terminal (sometimes appearing lateral) panicles of few to many heads, sympodial;

bracteoles absent proximal to perianth.

glomerules 3–12, each with (1–)2–5 flowers, open, branches unequal, 3–12 cm, primary bract terete or slightly compressed, shorter to longer than inflorescence.
Flowers

in few-flowered heads.

tepals straw-colored to pale green, ovate-lanceolate, 4–5 mm, apex acuminate or setaceous;

inner series elliptic, nearly equal, margins wide, scarious, apiculate;

stamens 6, filaments 1 mm, anthers 1.5–2 mm;

style 1 mm.
Capsules

3-locular or pseudo-3-locular.

tan to light reddish brown, 3-locular, ellipsoid, 3.7–4.5 ×1.6–2 mm, mostly shorter than or nearly equal to perianth.
Seeds

usually tailed (not tailed in J. roemerianus).

dark amber, obovoid, body 0.7–1 mm, tails 0.1–0.5 mm.

Juncus subg. Juncus

Juncus cooperi
Phenology Flowering and fruiting spring–summer.
Habitat Saline flats and meadows or edges of salt marshes
Elevation below 600 m (below 2000 ft)
Distribution
Worldwide; coastal in North America
from FNA
AZ; CA; NV; UT; Mexico
[BONAP county map]
Discussion

Species 9 (4 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Capsules 3.5–5 mm; plants of sw United States.
→ 2
1. Capsules less than 3.5 mm, shorter than or nearly equal to perianth; plants of ne United States Atlantic Coast.
→ 3
2. Capsules nearly globose, obviously longer than perianth
J. acutus subsp. leopoldii
2. Capsules ellipsoid, nearly equal to or shorter than perianth
J. cooperi
3. Capsules nearly equal to perianth; seeds tailed
J. maritimus
3. Capsules distinctly shorter than perianth; seed not tailed
J. roemerianus
Source FNA vol. 22. FNA vol. 22.
Parent taxa Juncaceae > Juncus Juncaceae > Juncus > subg. Juncus
Sibling taxa
J. acuminatus, J. acutiflorus, J. acutus, J. alpinoarticulatus, J. anthelatus, J. arcticus, J. articulatus, J. biglumis, J. bolanderi, J. brachycarpus, J. brachycephalus, J. brachyphyllus, J. brevicaudatus, J. bryoides, J. bufonius, J. bulbosus, J. caesariensis, J. canadensis, J. capillaris, J. capitatus, J. castaneus, J. chlorocephalus, J. compressus, J. confusus, J. coriaceus, J. covillei, J. debilis, J. dichotomus, J. diffusissimus, J. drummondii, J. dubius, J. dudleyi, J. effusus, J. elliottii, J. ensifolius, J. falcatus, J. filiformis, J. filipendulus, J. georgianus, J. gerardii, J. greenei, J. gymnocarpus, J. hallii, J. hemiendytus, J. howellii, J. inflexus, J. interior, J. kelloggii, J. leiospermus, J. lesueurii, J. longistylis, J. luciensis, J. macrandrus, J. macrophyllus, J. marginatus, J. maritimus, J. megacephalus, J. mertensianus, J. militaris, J. nevadensis, J. nodatus, J. nodosus, J. occidentalis, J. orthophyllus, J. oxymeris, J. parryi, J. patens, J. pelocarpus, J. pervetus, J. phaeocephalus, J. polycephalus, J. regelii, J. repens, J. roemerianus, J. scirpoides, J. secundus, J. squarrosus, J. stygius, J. subcaudatus, J. subtilis, J. supiniformis, J. tenuis, J. texanus, J. textilis, J. tiehmii, J. torreyi, J. trifidus, J. triformis, J. triglumis, J. trigonocarpus, J. uncialis, J. validus, J. vaseyi, J. xiphioides
Subordinate taxa
J. acutus subsp. leopoldii, J. cooperi, J. maritimus, J. roemerianus
Synonyms J. section Acuti, J. section Juncastrum, J. section Maritimi, J. section Thalassii, J. subg. Juncastrum, J. subg. Thalassii
Name authority unknown Engelmann
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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