Flora of North America species comparison

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Juncus effusus

Juncus subg. Genuini

common bog rush, common rush, common soft rush, pasture rush, soft or lamp rush, soft rush
Habit Herbs, perennial, 4–13 dm. Herbs, perennial, rhizomatous.
Rhizomes

short -branched, forming distinct, often large clumps.

Culms

erect, terete, 1–2.5 mm diam. at top of sheaths.

terete.
Cataphylls

several.

Leaves

blade absent.

basal;

blade usually absent, rarely present (J. hallii and J. parryi), if present terete, channeled, not septate.
Inflorescences

lateral, compound dichasia, many flowered;

primary bract erect, terete, extending well beyond dichasium.

lateral cymes, sympodial;

bracts erect, terete, appearing to be continuation of culms;

bracteoles 2, at base of perianth.
Flowers

tepals tan or darker, usually with greenish midstripe, lanceolate, 1.9–3.5 mm;

inner slightly shorter;

stamens 3, filaments 0.5–0.8 mm, anthers 0.5–0.8 mm;

style 0.2 mm.

borne singly, not in heads.
Capsules

greenish tan or darker, 3-locular, broadly ellipsoid to oblate, 1.5–3.2 mm.

3-locular.
Seeds

amber, (0.3–)0.4–0.5 mm.

usually not tailed.
2n

= 40, 42.

Juncus effusus

Juncus subg. Genuini
Phenology Flowering summer, fruiting summer–fall.
Habitat Swamps and their edges, marshes, moist meadows, and moist or saturated soils, often conspicuous in pasture meadows where it is shunned by grazing animals
Elevation Habitat??; 0–2500 m (Habitat??; 0–8200 ft)
Distribution
from FNA
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; NE; NH; NJ; NV; NY; OH; OK; OR; PA; RI; SC; TN; TX; VA; VT; WA; WI; WV; WV; BC; MB; NB; NF; NS; ON; PE; QC
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[BONAP county map]
Worldwide
Discussion

The Juncus effusus complex has been variously recognized as containing several species or a single species with numerous infraspecific taxa. Unfortunately, North American treatments have dealt primarily with taxa in either the eastern or western portions of the continent. In considering the continent as a whole, little sense can be made of these treatments. The North American J. effusus complex is one that is in obvious need of modern systematic scrutiny.

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

Species ca. 25 (11 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Flowers 1–3(–5); seeds tailed.
→ 2
1. Flowers more than 5.
→ 4
2. Leaf blade reduced to bristle
J. drummondii
2. Leaf blade well developed.
→ 3
3. Perianth 6–9 mm; capsules oblong, acute
J. parryi
3. Perianth 4–5 mm; capsules ovoid, retuse
J. hallii
4. Culms well spaced along sparingly branched creeping rhizomes.
→ 5
4. Culms tufted on short, densely branching rhizomes.
→ 8
5. Anthers shorter than filaments; tepals greenish; capsules green to light brown
J. filiformis
5. Anthers equal to or longer than filaments.
→ 6
6. Fruits acute.
→ 7
6. Fruits obtuse
J. textilis
7. Perianth usually 3–6 mm
J. arcticus
7. Perianth (5–)6–8 mm
J. lesueurii
8. Stamens 3
J. effusus
8. Stamens 6.
→ 9
9. Plants cespitose, stooling; capsules 3–4 mm
J. inflexus
9. Plants cespitose, not stooling; capsules less than 3 mm.
→ 10
10. Perianth much shorter than capsule; seeds 0.7–1 mm
J. gymnocarpus
10. Perianth equal to or exceeding capsule; seeds 0.4–0.5 mm
J. patens
Source FNA vol. 22. FNA vol. 22.
Parent taxa Juncaceae > Juncus > subg. Genuini Juncaceae > 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. cooperi, J. coriaceus, J. covillei, J. debilis, J. dichotomus, J. diffusissimus, J. drummondii, J. dubius, J. dudleyi, 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. arcticus, J. drummondii, J. effusus, J. filiformis, J. gymnocarpus, J. hallii, J. inflexus, J. lesueurii, J. parryi, J. patens, J. textilis
Synonyms J. conglomeratus, J. effusus var. brunneus, J. effusus var. caeruleomontanus, J. effusus var. costulatus, J. effusus var. dicipiens, J. effusus var. exiguus, J. effusus var. gracilis, J. effusus var. pylaei, J. effusus var. solutus, J. effusus var. subglomeratus, J. griscomii J. section Genuini, J. section Juncotypus, J. subg. Juncotypus
Name authority Linnaeus: Sp. Pl. 1: 326. (1753) Buchenau: Abhandlungen herausgegeben vom naturwissenschaftlichen Vereine zu Bremen 4: 406. (1875)
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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