Ruellia squarrosa (Fenzl) Cuf., Acanthaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  High risk, score: 7 (Go to the risk assessment).

Other Latin names:  Dipteracanthus squarrosus Fenzl

Habit:  shrub

Description:  "Sprawling perennial shrub with branches to 60 cm long, densely white-pilose (some hairs with small glandular apex). Leaf blades ovate to narrow-ovate, to 6 cm long and 2 cm wide, attenuate at base, entire, acute apically; younger leaves densely white-pilose, sparser with age; petioles to 2 cm long. Inflorescence axillary, solitary; bracteoles linear, 4.5-9 mm long, much shorter than calyx, pubescence as on stems and leaves but usually glandular. Flowers on pedicel to 1 mm long; calyx 10-16 mm long, with linear lobes joined only at the very base, reflexed after fruit is lost; corolla blue, finely pubescent externally on tube, throat and veins of lobes; tube c. 25 mm long; throat c. 12 mm long, curved slightly; lobes c. 15 mm long, more or less equal. Stamens with filaments c. 10 and 14 mm long. Stigma very unequally 2-lobed. Capsule 12-15 mm long, glabrous, 16-20-seeded, very shortly stipitate; seed c. 2 mm in diameter, thickened rim with mucilaginous hairs"  (PlantNET:  New South Wales Flora Online).

Habitat/ecology:  (no habitat/ecology info known by PIER)

Propagation:  Seed

Native range:  "Mexico (Veracruz) [possibly native here if Wasshausen's view is correct]"; cultivated elsewhere (GRIN).

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	O‘ahu Island		Bishop Museum (U.S.A. Hawaii. Honolulu.) (1960) (voucher ID: BISH 20089) Taxon name on voucher: Ruellia squarrosa (Fenzl) Cuf.
State of Hawaii Hawaiian Islands	O‘ahu Island		Bishop Museum (U.S.A. Hawaii. Honolulu.) (2001) (voucher ID: BISH 771824) Taxon name on voucher: Ruellia squarrosa (Fenzl) Cuf.
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced cultivated	MacKee, H. S. (1994) (p. 9) Voucher cited: MacKee 21262

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)	New South Wales	introduced invasive cultivated	National Herbarium of New South Wales (2011)
Australia Australia (continental)	Queensland	introduced invasive	National Herbarium of New South Wales (2011) "Naturalised in SE Qld (as a garden escape)&uot;.
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 189)
Mexico Mexico	Mexico (United Mexican States)	possibly native	U.S. Dept. Agr., Agr. Res. Serv. (2011) Veracruz

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Meyer, Jean-Yves/Lavergne, Christophe (2004) (p. 346)

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

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

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

References:

Bishop Museum (U.S.A. Hawaii. Honolulu.). 1960. Voucher specimen #BISH20089(Potter, C. s.n.).

Bishop Museum (U.S.A. Hawaii. Honolulu.). 2001. Voucher specimen #BISH771824(Imada, C. 2001-48).

MacKee, H. S. 1994. Catalogue des plantes introduites et cultivées en Nouvelle-Calédonie. Muséum National d'Histoire Naturelle, Paris, 164 p.

Meyer, Jean-Yves/Lavergne, Christophe. 2004. Beautés fatales: Acanthaceae species as invasive alien plants on tropical Indo-Pacific Islands. Diversity and Distributions 10 (2004): 333-347.

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.

National Herbarium of New South Wales. 2011. PlantNet: New South Wales Flora online. The Plant Information Network System of the Botanic Gardens Trust Version 2.0. Online resource.

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