OregonFlora: Juncus acutus vs. Juncus patens

	Juncus acutus	Juncus patens
		gray rush, spreading rush
Habit		Plants perennial, 30–90 cm tall, cespitose, fresh stems ridged, dull, blue-green, with (8)10–15 prominent strong ridges visible per side when dried, pith of fertile stems solid.
Leaves		without blades; distal sheaths 4–10 cm, green to pale brown distally; dull or shiny; smooth; apex symmetrical; thin, not winged.
Inflorescences		a well-developed; loose cluster of 10–100+ flowers; branches usually visible; inflorescence bracts not swollen.
Flowers		tepals 6, green to pale brown; tips acute; stamens 6; filaments 0.5–1 mm; anthers 0.4–0.65 mm; styles 0.1 mm.
Capsules		subglobose, 2–2.7 mm, pale brown; apex rounded or subacute; styles deciduous or inconspicuous; capsule shorter than the tepals, 1-chambered.
Seeds		0.4–0.5 × 0.2–0.3 mm, apiculate.

	Juncus acutus	Juncus patens
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion		Shores, floodplains, wet prairies, wet forest, swales, marshes, ditches. 0–1000 m. Casc, CR, Sisk, WV. CA, WA; south to Mexico. Native. The blue-green stems separate J. patens from all other cespitose species in Group 2, except the rare exotic J. inflexus, which has a chambered pith and dark tepals. However, the Australian introduction J. usitatus L.A.S. Johnson has become an invasive pest in northern California, where it has been mistakenly used in native plant restoration work and landscaping because it closely resembles J. patens. They are separable by the blunt not acute petals of J. usitatus, its three stamens per flower, and its tepals much shorter than the capsules. Juncus patens has six stamens per flower, and its tepals are longer than the capsules.
Source		Flora of Oregon, volume 1, page 282 Peter Zika
Sibling taxa	J. acuminatus, J. anthelatus, J. articulatus, J. balticus, J. bolanderi, J. brevicaudatus, J. breweri, J. bryoides, J. bufonius, J. bulbosus, J. canadensis, J. capillaris, J. capitatus, J. compressus, J. confusus, J. conglomeratus, J. covillei, J. diffusissimus, J. drummondii, J. dudleyi, J. effusus, J. ensifolius, J. ensifolius x Juncus nevadensis, J. exiguus, J. falcatus, J. filiformis, J. gerardi, J. hemiendytus, J. hesperius, J. howellii, J. inflexus, J. interior, J. kelloggii, J. laccatus, J. lescurii, J. longistylis, J. marginatus, J. mertensianus, J. mexicanus, J. nevadensis, J. occidentalis, J. orthophyllus, J. oxymeris, J. parryi, J. patens, J. pelocarpus, J. planifolius, J. ranarius, J. regelii, J. saximontanus, J. supiniformis, J. tenuis, J. tiehmii, J. torreyi, J. triglumis, J. trilocularis, J. uncialis	J. acuminatus, J. anthelatus, J. articulatus, J. balticus, J. bolanderi, J. brevicaudatus, J. breweri, J. bryoides, J. bufonius, J. bulbosus, J. canadensis, J. capillaris, J. capitatus, J. compressus, J. confusus, J. conglomeratus, J. covillei, J. diffusissimus, J. drummondii, J. dudleyi, J. effusus, J. ensifolius, J. ensifolius x Juncus nevadensis, J. exiguus, J. falcatus, J. filiformis, J. gerardi, J. hemiendytus, J. hesperius, J. howellii, J. inflexus, J. interior, J. kelloggii, J. laccatus, J. lescurii, J. longistylis, J. marginatus, J. mertensianus, J. mexicanus, J. nevadensis, J. occidentalis, J. orthophyllus, J. oxymeris, J. parryi, J. pelocarpus, J. planifolius, J. ranarius, J. regelii, J. saximontanus, J. supiniformis, J. tenuis, J. tiehmii, J. torreyi, J. triglumis, J. trilocularis, J. uncialis
Web links	Local Web sites: Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, 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 patens

gray rush, spreading rush

Habit

Plants perennial, 30–90 cm tall, cespitose, fresh stems ridged, dull, blue-green, with (8)10–15 prominent strong ridges visible per side when dried, pith of fertile stems solid.

Leaves

without blades;

distal sheaths 4–10 cm, green to pale brown distally; dull or shiny; smooth;

apex symmetrical; thin, not winged.

Inflorescences

a well-developed; loose cluster of 10–100+ flowers;

branches usually visible;

inflorescence bracts not swollen.

Flowers

tepals 6, green to pale brown;

tips acute;

stamens 6;

filaments 0.5–1 mm;

anthers 0.4–0.65 mm;

styles 0.1 mm.

Capsules

subglobose, 2–2.7 mm, pale brown;

apex rounded or subacute;

styles deciduous or inconspicuous; capsule shorter than the tepals, 1-chambered.

Seeds

0.4–0.5 × 0.2–0.3 mm, apiculate.

Juncus acutus

Juncus patens

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Shores, floodplains, wet prairies, wet forest, swales, marshes, ditches. 0–1000 m. Casc, CR, Sisk, WV. CA, WA; south to Mexico. Native.

The blue-green stems separate J. patens from all other cespitose species in Group 2, except the rare exotic J. inflexus, which has a chambered pith and dark tepals. However, the Australian introduction J. usitatus L.A.S. Johnson has become an invasive pest in northern California, where it has been mistakenly used in native plant restoration work and landscaping because it closely resembles J. patens. They are separable by the blunt not acute petals of J. usitatus, its three stamens per flower, and its tepals much shorter than the capsules. Juncus patens has six stamens per flower, and its tepals are longer than the capsules.

Source

Flora of Oregon, volume 1, page 282
Peter Zika

Sibling taxa