Juncus spp. Juncaceae

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Present on Pacific Islands?  yes

Threat only at high elevations?  no

Risk assessment results:  Reject, score: 15 (Go to the risk assessment for Juncus acutus)

Habit:  rush

Description:  "Rhizomatous perennial or rarely annual herbs; stems rounded or sometimes somewhat flattened. Leaves cauline or primarily basal, glabrous, blades flat or grooved on upper surface, or terete and hollow, or laterally compressed, sword-shaped, septate, or absent, sheaths open or rarely closed. Flowers usually perfect, in open or very dense cymes, these racemose, paniculate, or glomerulate, or sometimes solitary; perianth parts green to yellowish brown or dark brown, more or less subtended by clasping bracteoles; stamens 3-6. Capsules 1-3 celled. Seeds 15-120 per capsule" (Wagner et al., 1999; pp. 1451-1454).

Habitat/ecology:  Wet sites, bogs and marshy areas. Naturalized from 800 m and above in Hawai‘i (Wagner et al., 1999; pp. 1451-1454).

Propagation:  Seed; local spread by rhizomes.

Native range:  Various

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
French Polynesia Tubuai (Austral) Islands	Raivavae (Raevavae) Island		Bishop Museum (Honolulu) (1934) (voucher ID: BISH 112410) Taxon name on voucher: Juncus (Genus of Juncaceae)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive	Oppenheimer, Hank L./Bartlett, Randal T. (2002) (p. 9) Juncus planifolius R. Br., voucher cited: Oppenheimer H109925 (BISH)
Solomon Islands Solomon Islands	Mikira (San Cristobal) Island		Bishop Museum (Honolulu) (1966) (voucher ID: BISH 604083) Taxon name on voucher: Juncus (Genus of Juncaceae)

Comments:  Species naturalized in Hawai‘i include J. acuminatus Michx. (Maui, Hawai‘i), J. bufonius L. (Kaua‘i, Moloka‘i, Maui, Hawai‘i), J. effusus L. (Moloka‘i, Maui, Hawai‘i), J. ensifolius Wikstr. (Maui, Hawai‘i), J. planifolius R. Br. (Kaua‘i, O‘ahu, Moloka‘i, Maui, Hawai‘i), J. polyanthemos Buchenau (O‘ahu (cult.), Maui) and J. tenuis Willd. (Kaua‘i, Moloka‘i, East Maui, Hawai‘i) (Wagner et al., 1999; pp. 1451-1454).
Species naturalized in Australia include J. acutiflorus Ehrh., J. acutus L., J. canadensis Gay and J. inflexus L. (Csurhes and Edwards, 1998; pp. 113, 172).
Species naturalized in New Zealand include J. acutus L., J.articulatus L., J. bulbosus L., J. effusus L. and J. squarrosus L. (Owen, 1997).

While more commonly temperate zone species, can be a threat at higher elevations, as in Hawai‘i.

Control: 

Chemical: "Difficult because of thick rhizomes and roots. Susceptible to 1-1.5% glyphosate applied to foliage (Hank Oppenheimer, Maui Pine)." (Motooka et al., 2002)

Additional information:
Additional online information about Juncus spp. is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Juncus spp. as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Juncus spp. may be available from the Germplasm Resources Information Network (GRIN).