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, lesser Jack, prickly dock, spiny emex, spiny threecornerjack

French: émex épineux

Spanish: romaza espinosa

Habit:  herb

Description:  "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)		Hafliger, Toni J./Wolf, Matthias (1988) (p. 273)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 181)

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)

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).

Additional information:
Excerpt from the book "Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide" (Motooka et al., 2003). (PDF format).

Additional online information about Emex spinosa is available from the Hawaiian Ecosystems at Risk project (HEAR).

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

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

References:

Hafliger, Toni J./Wolf, Matthias. 1988. Dicot weeds, vol. 1. CIBA-GEIGY Ltd., Basle, Switzerland. 335 pp.

Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp.

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

Motooka, Philip/Castro, Luisa/Nelson, Duane/Nagai, Guy/Ching, Lincoln. 2003. Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. 184 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

U.S. Dept. Agr., Nat. Res. Cons. Serv. 2011. The PLANTS Database. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).