FNA: Juncus acutus vs. Juncus biglumis

	Juncus acutus	Juncus biglumis
	sharp rush, spiny rush	two-flower rush, two-glumed rush
Habit		Herbs, perennial, loosely cespitose, 0.25–1.6 dm.
Culms		nearly terete.
Cataphylls		2–4.
Leaves		basal, 1–4; sheaths loose; auricles absent or rounded, 0.5 mm; blade imperfectly septate, ascending, nearly terete, 2–7 cm × 0.5–1.5 mm.
Inflorescences		heads, 1–2(–4)-flowered; primary bracts much longer than inflorescence.
Flowers		tepals brown to blackish, oblong, 2.5–4 mm, apex obtuse; outer and inner series nearly equal; stamens 6, filaments 1–1.5 mm, anthers 0.5–0.7 mm; style deciduous, 0.3–0.4 mm.
Capsules		pale with dark purplish valve margins, pseudo-3-locular, oblate to narrowly ovoid, 4–5.5 × 1.7–2.3 mm, exceeding perianth, apex retuse.
Seeds		yellowish tan, fusiform-ovoid, 0.7–0.9 mm, short tailed.
2n		= 120.

	Juncus acutus	Juncus biglumis
Phenology		Flowering and fruiting summer.
Habitat		Wet tundra and mossy margins of ponds and streams, wet gravel and open, rocky slopes in alpine zones
Elevation		10–3400 m (0–11200 ft)
Distribution	AZ; CA; NV; South America; Mexico (Baja Calif); South Africa; Atlantic Islands [WildflowerSearch map] [BONAP county map]	AK; CO; MT; WY; AB; BC; LB; MB; NT; NU; ON; QC; YT; Greenland; n Europe; Asia [BONAP county map]
Discussion	Subspecies 2 (1 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.)
Source	FNA vol. 22, p. 237.	FNA vol. 22.
Parent taxa	Juncaceae > Juncus > subg. Juncus	Juncaceae > Juncus > subg. Alpini
Sibling taxa	J. acuminatus, J. acutiflorus, 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. 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	J. acuminatus, J. acutiflorus, J. acutus, J. alpinoarticulatus, J. anthelatus, J. arcticus, J. articulatus, 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. 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
Name authority	Linnaeus: Sp. Pl. 1: 325. (1753)	Linnaeus: Sp. Pl. 1: 328. (1753)
Web links	Local Web sites: CalFlora, CalPhotos WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC Local Web sites: PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Juncus acutus

Juncus biglumis

sharp rush, spiny rush

two-flower rush, two-glumed rush

Habit

Herbs, perennial, loosely cespitose, 0.25–1.6 dm.

Culms

nearly terete.

Cataphylls

2–4.

Leaves

basal, 1–4;

sheaths loose;

auricles absent or rounded, 0.5 mm;

blade imperfectly septate, ascending, nearly terete, 2–7 cm × 0.5–1.5 mm.

Inflorescences

heads, 1–2(–4)-flowered;

primary bracts much longer than inflorescence.

Flowers

tepals brown to blackish, oblong, 2.5–4 mm, apex obtuse;

outer and inner series nearly equal;

stamens 6, filaments 1–1.5 mm, anthers 0.5–0.7 mm;

style deciduous, 0.3–0.4 mm.

Capsules

pale with dark purplish valve margins, pseudo-3-locular, oblate to narrowly ovoid, 4–5.5 × 1.7–2.3 mm, exceeding perianth, apex retuse.

Seeds

yellowish tan, fusiform-ovoid, 0.7–0.9 mm, short tailed.

= 120.

Juncus acutus

Juncus biglumis

Phenology

Flowering and fruiting summer.

Habitat

Wet tundra and mossy margins of ponds and streams, wet gravel and open, rocky slopes in alpine zones

Elevation

10–3400 m (0–11200 ft)

Distribution

AZ; CA; NV; South America; Mexico (Baja Calif); South Africa; Atlantic Islands

[WildflowerSearch map]

[BONAP county map]

AK; CO; MT; WY; AB; BC; LB; MB; NT; NU; ON; QC; YT; Greenland; n Europe; Asia

[BONAP county map]

Discussion

Subspecies 2 (1 in the flora).

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

Source

FNA vol. 22, p. 237.

FNA vol. 22.

Parent taxa

Juncaceae > Juncus > subg. Juncus

Juncaceae > Juncus > subg. Alpini

Sibling taxa

J. acuminatus, J. acutiflorus, 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. 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

J. acuminatus, J. acutiflorus, J. acutus, J. alpinoarticulatus, J. anthelatus, J. arcticus, J. articulatus, 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. 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

Name authority

Linnaeus: Sp. Pl. 1: 325. (1753)

Linnaeus: Sp. Pl. 1: 328. (1753)

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).

Choose a data source: Flora of North America

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Flora of North America species comparison

Juncus acutus

Juncus biglumis

Juncus acutus

Juncus biglumis