OregonFlora: Juncus acutus vs. Juncus filiformis

	Juncus acutus	Juncus filiformis
		thread rush
Habit		Plants perennial, 10–80 cm tall, rhizomatous, stem ridges obscure.
Leaves		lacking blades; distal sheaths 3–10 cm, light brown.
Inflorescences		a more or less loose cluster of 4–15 flowers, usually attached near or below middle of stems (stems here including erect inflorescence bracts above inflorescences); inflorescence bracts not swollen at base.
Flowers		tepals 6, green or pale brown, 2.5–4 mm; stamens 6; filaments 0.4–0.9 mm; anthers 0.3–0.6 mm; styles 0.1– 0.15 mm.
Capsules		2.5–3.5 mm; shorter than or equaling the length of the tepals, green to light brown; apex obtuse to acute, 3-chambered.
Seeds		0.4–0.5 × 0.2–0.25 mm.
2n		=70, 80, 84.

	Juncus acutus	Juncus filiformis
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion		Pond shores, wet meadows, marshes. 800–2300 m. BW, Casc. ID, WA; northern North America; Eurasia. Native.
Source		Flora of Oregon, volume 1, page 278 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. 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
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: BC, OR, WA 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

Juncus acutus

Juncus filiformis

thread rush

Habit

Plants perennial, 10–80 cm tall, rhizomatous, stem ridges obscure.

Leaves

lacking blades;

distal sheaths 3–10 cm, light brown.

Inflorescences

a more or less loose cluster of 4–15 flowers, usually attached near or below middle of stems (stems here including erect inflorescence bracts above inflorescences);

inflorescence bracts not swollen at base.

Flowers

tepals 6, green or pale brown, 2.5–4 mm;

stamens 6;

filaments 0.4–0.9 mm;

anthers 0.3–0.6 mm;

styles 0.1– 0.15 mm.

Capsules

2.5–3.5 mm; shorter than or equaling the length of the tepals, green to light brown;

apex obtuse to acute, 3-chambered.

Seeds

0.4–0.5 × 0.2–0.25 mm.