Emex spinosa (L.) Campd., Polygonaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Other Latin names:  Rumex spinosus L.

Common name(s): [more details]

English: devil's thorn, erect emex, lesser Jack, little jack, prickly dock, spiny emex, spiny threecornerjack

French: émex épineux

Spanish: romaza espinosa

Habit:  herb

Description:  "Plants 3-6(-8) dm. Stems as-cending to erect, base often reddish, branched proximally. Leaves: ocrea loose, glabrous; petiole 2-29 cm, glabrous; blade ovate to ovate-oblong or triangu-lar, 3-13 x 1.1-12 cm, base mostly truncate to subcordate, apex obtuse to acute. Staminate flowers 1-8 per ocreate fascicle; tepals narrowly oblong to oblanceolate, 1.5-2 mm. Pistillate flowers 2-7 per ocreate fascicle; outer tepals ovate to oblong, 4-6 mm in fruit, inner tepals linear-lanceolate, 5-6 mm in fruit, apex acute. Fruiting perianths 5-6 x 5-6 mm, spines spreading to reflexed, 2-4 mm, base broad. Achenes 4-5 x 2-3 mm, shiny"  (Flora of North America online).

"Annual herbs 3-8 dm tall; stems decumbent to ascending.  Leaves ovate to nearly deltate, 5-42 cm long, 1.1-12 cm wide, glabrous, petioles 2-29 cm long.  Staminate flowers in terminal and axillary, pedunculate clusters, tepals narrowly oblong-oblanceolate, ca. 1.5-2 mm long; pistillate flowers axillary, sessile, outer tepals ca. 4-6 mm long in fruit, tipped with divergent spines, inner ones erect, 5-6 mm long.  Nuts pale brown, glossy, ca. 4 mm long"  (Wagner et al., 1999; p. 1060).

Habitat/ecology:  In Hawai‘i, "naturalized in open, dry to mesic, disturbed habitats, 150-1,950 m" (Wagner et al., 1999; p. 1060).

Propagation:  Seed

Native range:  Mediterranean region (Wagner et al., 1999; p. 1060).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1060)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1060)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1060) Voucher cited: Degener 18174 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1060)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Australia (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalised
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 181)
United States (west coast) United States (west coast states)	USA (California)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 141)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013) Massachusetts, New Jersey, Texas
United States (continental except west coast) United States (other states)	USA (Florida)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)

Comments:  See also Emex australis.

Control: 

Physical:  "Sanitation is important in preventing the spread of spiny emex.  The spiny fruits stick to soles of shoes and to vehicle tires"  (Motooka et al., 2003).

Chemical: "Very sensitive to dicamba; 0.25 lb./acre sufficient to kill all treated plants"  (Motooka et al., 2003).