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Juncus ensifolius

Wikstr. (1824)

This name is accepted

Kingdom: Viridiplantae Phylum: Magnoliophyta Class/Clade: Monocots Order: Poales Family: Juncaceae Genus: Juncus

bog rush, rush

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Description

Key Characters:

Growth Form: Perennial herbs.

Stems: Stems green, striate, compressed, 2–6 dm long, arising singly from horizontal rhizomes.

Roots:

Leaves: Leaves simple. Blades 7–15 cm long, 2–5 mm wide. Surfaces pale green, primarily basal, usually equitant, laterally flattened, becoming terete (cylindrical) toward apex, septa incomplete. Margins entire. Sheaths with thin hyaline margins, not prolonged into auricles. Stipules absent.

Flowers: Flowers 3–12 in clusters, these arranged in 4–12 terminal glomerules, inflorescences 1–7 cm long, branches usually strict, pedicels short, lowest bract leaf-like, up to ½ as long as inflorescence or longer, 1 bract subtending each pedicel, hyaline. Flowers bisexual (perfect). Perianth parts dark reddish brown, lanceolate, ca. 3 mm long, apex acuminate, outer ones slightly longer than inner ones. Stamens 3, shorter than perianth; anthers shorter than filaments. Pollen grains remaining in tetrads, surrounded by a common exine. Ovary superior, carpels 1.

Fruit: Capsules dark glossy brown; 3–angled; oblong; slightly longer than perianth; with a short style beak splitting after capsules body. Seeds rusty orange; broadly fusiform; slightly apiculate at 1 or both ends; 0.3–0.4 mm long.

Ploidy: 2n = 40

Habitat: naturalized in standing water of marshy areas.

Elevation Range:

Historical Distribution

Images

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Uses and Culture

USES

Natural History

Statewide Status

Naturalized

Island Status

Molokai Not in flora
Maui Naturalized
Hawai'i Naturalized

Dispersal Agents


Pollinators

Bibliography

Name Published In: Kongl. Vetensk. Acad. Handl. 1824(2): 1 (1824)

Other References

Wagner et al. 1990:1453 (M? [reported but no spm.], H); Oppenheimer 2004:13 (EM); Faccenda & Daehler 2024:35 (Mo); Faccenda, Arthur, et al. 2025:187 (remove Mo [re-IDed as J. prismatocarpus subsp. prismatocarpus], KEY)

Occurrences

SNo. Scientific Name Locality Habitat Basis of Record Description Recorded By Record Number Island Source Date
1 Juncus ensifolius East Maui, Makawao District, Ko'olau Gap, west side second cove down fron Ainahou, area locally known as Halehaku, but not Halehaku Stream as shown on maps. Growning in saturated ground in opening in Metrosideros Forest in sunny area at margin of ephermeral lake with Holcus, Ageratina, Carex, Prunella, and Rubus Preserved_Specimen Oppenheimer, H.L. 41407 Maui BISH 2014-04-09
2 Juncus ensifolius East of Ukulele Preserved_Specimen Forbes, C.N. 901 Maui BISH 1919-07-21
3 Juncus ensifolius Near Kalauilehua, at 29 miles Preserved_Specimen Rock, J.F.C. 12535 Hawaii BISH 1911-01-01
4 Juncus ensifolius Keauhou Ranch, Logging Rd. in pasture adjacent to Kilauea Forest Reserve In pasture. Preserved_Specimen Stemmermann, R.L. Hawaii BISH 1980-12-27
5 Juncus ensifolius North Kohala District; Hawi Quadrangle, Parker Ranch. Stock ponds in vicinity of Kehena Reservoir Emergent vegetation growing along shore & standing water. Floating submergent. Preserved_Specimen Engilis Jr., A. 9209 Hawaii BISH 1992-06-08
6 Juncus ensifolius Huehue Ranch, above Holualoa, N. Kona, Hawaii Wet, open pasture. Preserved_Specimen Locally called wild iris + considered good cattle fodder Greenwell, A.B.H. 21377 Hawaii BISH 1951-04-25
7 Juncus ensifolius N Hilo District, Humuula, near head of Wailuku River Growing under Sophora tree. Preserved_Specimen Herb. Herbst, D.R. 6142 Hawaii BISH 1978-07-12
8 Juncus ensifolius Hilo entrance to Hawaii National Park Growing in standing water in marshy area. Infrequent. Preserved_Specimen Roots joined together. Fagerlund, G.O. 820 Hawaii BISH 1943-08-27
9 Juncus ensifolius N Hilo District, Humuula, near head of Wailuku River Growing under Sophora tree. Preserved_Specimen Herb. Herbst, D.R. 6142 Hawaii BISH 1978-07-12
10 Juncus ensifolius N Hilo District, Humuula, near head of Wailuku River Growing under Sophora tree. Preserved_Specimen Herb. Herbst, D.R. 6142 Hawaii BISH 1978-07-12
11 Juncus ensifolius North Kohala District; Hawi Quadrangle, Parker Ranch. Stock ponds in vicinity of Kehena Reservoir Emergent vegetation growing along shore & standing water. Floating submergent. Preserved_Specimen Engilis Jr., A. 9217 Hawaii BISH 1992-06-08
12 Juncus ensifolius North Kohala District; Hawi Quadrangle, Parker Ranch. Stock ponds in vicinity of Kehena Reservoir OBSERVATION Curtis Daehler Hawaii HAPI 3/17/2007
13 Juncus ensifolius N Hilo District, Humuula, near head of Wailuku River Growing under Sophora tree. Preserved_Specimen Herb. Herbst, D.R. 6142 Hawaii BISH 1978-07-12
14 Juncus ensifolius East Maui, Makawao District, Waikamoi. ... Growing in small gully along trail from Hosmer Grove to boardwalk Growing in small gully Preserved_Specimen Oppenheimer, H.L. 100204 Maui BISH 2002-10-20
15 Juncus ensifolius North Kohala District; Hawi Quadrangle, Parker Ranch. Stock ponds in vicinity of Kehena Reservoir OBSERVATION Curtis Daehler Hawaii HAPI 3/21/2007
16 Juncus ensifolius East Maui, Makawao District, mauka of Ukulele, along W boundary of Waikamoi Preserve Occasional in muddy areas in pasture and remnant Koa/Ohia Forest, with Holcus lanatus. Preserved_Specimen Oppenheimer, H.L. 90617 Maui BISH 2006-09-19
17 Juncus ensifolius East Maui, TNCʻs Waikamoi preserve, Upper Waikamoi, Contour Trail West of Honomanu Gulch Edge of forest and shrubland. Boggy/wet puddle zone in shallow drainage bottom, common in similiar habitats along contour trail. Forest margin w/ subalpine shrubland: Metrosideros, Cheirodendron, Leptecophylla, Dryopteris, Holcus, Luzula, Prunella, Carex Preserved_Specimen Z. Pezzillo 1160 Maui BISH 2025-05-19
18 Juncus ensifolius Piihonua; Hilo Forest Reserve, Site 23 OS Stunted ohia wetland dieback; assoc. spp.: Metrosideros polymorpha, Ilex anomala, Myrsine lessertiana, M. sandwicensis, Cheirodendron trigynum & Pelea clusiifolia. Soil a moderately deep yet poorly drained organic/ash found on a pahoehoe flow. Preserved_Specimen Adee, K.T. Hawaii BISH 1978-09-26
19 Juncus ensifolius Near Kalauilehua, at 29 miles Preserved_Specimen Rock, J.F.C. 12535 Hawaii BISH 1911-01-01
20 Juncus ensifolius East Maui, Makawao District, Ko'olau Gap, west side second cove down fron Ainahou, area locally known as Halehaku, but not Halehaku Stream as shown on maps. Growning in saturated ground in opening in Metrosideros Forest in sunny area at margin of ephermeral lake with Holcus, Ageratina, Carex, Prunella, and Rubus Preserved_Specimen Oppenheimer, H.L. 41407 Maui BISH 2014-04-09
21 Juncus ensifolius East of Ukulele Preserved_Specimen Forbes, C.N. 901 Maui BISH 1919-07-21
22 Juncus ensifolius Near Kalauilehua, at 29 miles Preserved_Specimen Rock, J.F.C. 12535 Hawaii BISH 1911-01-01
23 Juncus ensifolius Keauhou Ranch, Logging Rd. in pasture adjacent to Kilauea Forest Reserve In pasture. Preserved_Specimen Stemmermann, R.L. Hawaii BISH 1980-12-27
24 Juncus ensifolius North Kohala District; Hawi Quadrangle, Parker Ranch. Stock ponds in vicinity of Kehena Reservoir Emergent vegetation growing along shore & standing water. Floating submergent. Preserved_Specimen Engilis Jr., A. 9209 Hawaii BISH 1992-06-08
25 Juncus ensifolius Huehue Ranch, above Holualoa, N. Kona, Hawaii Wet, open pasture. Preserved_Specimen Locally called wild iris + considered good cattle fodder Greenwell, A.B.H. 21377 Hawaii BISH 1951-04-25
26 Juncus ensifolius N Hilo District, Humuula, near head of Wailuku River Growing under Sophora tree. Preserved_Specimen Herb. Herbst, D.R. 6142 Hawaii BISH 1978-07-12
27 Juncus ensifolius Hilo entrance to Hawaii National Park Growing in standing water in marshy area. Infrequent. Preserved_Specimen Roots joined together. Fagerlund, G.O. 820 Hawaii BISH 1943-08-27
28 Juncus ensifolius N Hilo District, Humuula, near head of Wailuku River Growing under Sophora tree. Preserved_Specimen Herb. Herbst, D.R. 6142 Hawaii BISH 1978-07-12
29 Juncus ensifolius N Hilo District, Humuula, near head of Wailuku River Growing under Sophora tree. Preserved_Specimen Herb. Herbst, D.R. 6142 Hawaii BISH 1978-07-12
30 Juncus ensifolius North Kohala District; Hawi Quadrangle, Parker Ranch. Stock ponds in vicinity of Kehena Reservoir Emergent vegetation growing along shore & standing water. Floating submergent. Preserved_Specimen Engilis Jr., A. 9217 Hawaii BISH 1992-06-08
31 Juncus ensifolius North Kohala District; Hawi Quadrangle, Parker Ranch. Stock ponds in vicinity of Kehena Reservoir OBSERVATION Curtis Daehler Hawaii HAPI 3/17/2007
32 Juncus ensifolius N Hilo District, Humuula, near head of Wailuku River Growing under Sophora tree. Preserved_Specimen Herb. Herbst, D.R. 6142 Hawaii BISH 1978-07-12
33 Juncus ensifolius East Maui, Makawao District, Waikamoi. ... Growing in small gully along trail from Hosmer Grove to boardwalk Growing in small gully Preserved_Specimen Oppenheimer, H.L. 100204 Maui BISH 2002-10-20
34 Juncus ensifolius North Kohala District; Hawi Quadrangle, Parker Ranch. Stock ponds in vicinity of Kehena Reservoir OBSERVATION Curtis Daehler Hawaii HAPI 3/21/2007
35 Juncus ensifolius East Maui, Makawao District, mauka of Ukulele, along W boundary of Waikamoi Preserve Occasional in muddy areas in pasture and remnant Koa/Ohia Forest, with Holcus lanatus. Preserved_Specimen Oppenheimer, H.L. 90617 Maui BISH 2006-09-19
36 Juncus ensifolius East Maui, TNCʻs Waikamoi preserve, Upper Waikamoi, Contour Trail West of Honomanu Gulch Edge of forest and shrubland. Boggy/wet puddle zone in shallow drainage bottom, common in similiar habitats along contour trail. Forest margin w/ subalpine shrubland: Metrosideros, Cheirodendron, Leptecophylla, Dryopteris, Holcus, Luzula, Prunella, Carex Preserved_Specimen Z. Pezzillo 1160 Maui BISH 2025-05-19
37 Juncus ensifolius Piihonua; Hilo Forest Reserve, Site 23 OS Stunted ohia wetland dieback; assoc. spp.: Metrosideros polymorpha, Ilex anomala, Myrsine lessertiana, M. sandwicensis, Cheirodendron trigynum & Pelea clusiifolia. Soil a moderately deep yet poorly drained organic/ash found on a pahoehoe flow. Preserved_Specimen Adee, K.T. Hawaii BISH 1978-09-26
38 Juncus ensifolius Near Kalauilehua, at 29 miles Preserved_Specimen Rock, J.F.C. 12535 Hawaii BISH 1911-01-01
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