Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Other Latin names:  Hyptis capitata var. mexicana Briq.; Hyptis capitata var. pilosa Briq.; Hyptis decurrens (Blanco) Epling

Common name(s): [more details]

English: knobweed

Habit:  herb

Description:  "Perennial herb 2 dm to 2 m tall, the stems often slightly decumbent and rooting at nodes, angles moderately hirsute with several-celled, irregularly curved hairs, intermarginal surfaces glabrous, lower internodes shorter than subtending leaves, the upper progressively longer, often exceeding leaves; petioles narrowly winged, to 4 cm long, wings gradually ampliate, merging into blades; leaf blades rhomboidally ovate to rhomboid-lanceolate, 3-12 cm long, 1-4 cm wide, acute to attenuate at apex, cuneate at base, coarsely and irregularly serrate, dark green and sparsely hispid above, paler, markedly pellucid-punctate and with more or less appressed, several-celled, coarse hairs along veins beneath, intervenous surfaces glabrous; inflorescences semiglobose, borne on axillary peduncles 1-5 cm long, peduncles hirsute; bracts lanceolate to oblanceolate, 6-12 mm long, acute to acuminate at apex, somewhat more densely hirsute than leaves, entire; flowers crowded in heads, sessile; calyx tube about 1.5-2 mm long, antrorsely short-ciliate, equal or nearly so; fruiting calyces coarsely reticulate-veined between ribs; corolla about 4 mm long, white, bearing hairs to 1 mm long on outer surfaces of upper part of tube and lobes, tube about 2 mm long, gradually  ampliate upward; upper pair of stamens slightly shorter than lower; nutlets about 1 mm long" (Wiggins & Porter, 1971; pp. 402-404).

"This species is closely related to H. capitata Jacq., but has somewhat narrower and smaller bracts below the heads of the flowers, and broader and shorter calyx teeth"  (Wiggins & Porter, 1971; pp. 402-404).

Habitat/ecology:  In New Guinea, "a weed of roadsides, waste land and pastureas; quite unpalatable to livestock and so, if unchecked, soon becoming dominant in grazing land" (Henty & Pritchard, 1975; p. 105). Moist uplands in the Galápagos Islands (McMullen, 1999; p. 252).

Propagation:  Seed

Native range:  Mexico (GRIN)

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Ecuador (Galápagos Islands) Isabela Group	Isabela Island	introduced invasive	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Isabela Group	Volcán Alcedo, Isabela Island	introduced invasive	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Isabela Group	Volcán Sierra Negra, Isabela Island	introduced invasive	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) San Cristóbal Group	San Cristóbal Island	introduced invasive	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Santa Cruz Group	Santa Cruz Island	introduced invasive	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Santiago Group	Santiago Island	introduced invasive	Charles Darwin Foundation (2008)
Papua New Guinea Papua New Guinea (eastern New Guinea Island)	Papua New Guinea (eastern New Guinea Island)	introduced invasive	Henty, E. E./Pritchard, G. H. (1975) (p. 105)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2009)

Comments:  Probably not native to the Galápagos Islands, possibly introduced, per Charles Darwin Research Station.

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

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

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

Other Latin names:  Hyptis capitata var. mexicana Briq.; Hyptis capitata var. pilosa Briq.; Hyptis decurrens (Blanco) Epling

References:

Charles Darwin Foundation. 2008. Database inventory of introduced plant species in the rural and urban zones of Galapagos. Charles Darwin Foundation, Galapagos, Ecuador.

Charles Darwin Research Station. 2005. CDRS Herbarium records.

Henty, E. E./Pritchard, G. H. 1975. Weeds of New Guinea and their control. 2nd edition. Department of Forests, Division of Botany, Botany Bull. No. 7. Lae, Papua New Guinea. 180 pp.

McMullen, C. K. 1999. Flowering plants of the Galápagos. Comstock Pub. Assoc., Ithaca, N.Y. 370 p.

U.S. Dept. Agr., Agr. Res. Serv. 2009. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Wiggins, I. L./Porter, D. M. 1971. Flora of the Galapágos Islands. Stanford University Press. 998 pp.