Robinia pseudoacacia L., Fabaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  yes

Common name(s): [more details]

Chinese: ci huai

English: Chinese scholar tree, acacia locust, black locust, false acacia, honey locust, locust tree, robinia, white acacia, white locust, yellow locust

French: acacia blanc, acacia des jardiniers, robinier, robinier faux-acacia

Spanish: falsa acacia, robinia

Habit:  tree

Description:  "Deciduous tree, to 25 m high; twigs puberulent when young, angled, usually with stout scattered stipular spines up to c. 1 cm long. Leaves glabrous to puberulent particularly below, petiolate; leaflets ovate to elliptic, acute or obtuse, sometimes shortly mucronate, in 4-10 ± opposite pairs, (10)-20-40-(50) mm long, stipellate; petiolules 2-5 mm long. Raceme with numerous flowers; pedicels 5-10 mm long. Calyx puberulent; calyx teeth unequal, broadly triangular. Corolla white with the base of standard greenish or yellowish, 15-23 mm long. Pod glabrous, irregularly oblong, 2-8-seeded, 35-80 mm long; seeds smooth, brown- spotted, oblong"   (Webb et al., 1988; p. 676).

"Arbre de 3 à 12 m de hauteur, pouvant atteindre 25 m dans sa région d’origine, reconnaissable à ses jeunes tiges munies de paires de longues épines, ses feuilles bipennées et ses inflorescences de fleurs blanches" (Meyer, 2008; p. 26).

Habitat/ecology:  "Forests, riparian habitats, grassland, rocky places.  This shade intolerant pioneer tree grows in a wide range of soils.  It is a variable species and many cultivars have been developed.  Seedlings establish in forest gaps and grow rapidly to reach the canopy.  The tree then spreads quickly by lateral growth and root sprouts, leading to dense pure stands that displace native vegetation.  The tree is nitrogen-fixing and increases soil fertility levels which may affect the floristic composition of invaded sites.  In Europe, it invades species-rich dry grasslands and reduces the abundance of species adapted to nutrient poor soils.  Damaged trees resprout vigorously from the base"  (Weber, 2003; p. 361).

In New Zealand, "waste places, scrubland, forest margins and clearings"  (Webb et al., 1988; p. 676).

"L’espèce a été introduite dans de nombreux pays tempérés et subtropicaux comme arbre d’ombrage, plante ornementale ou fourragère, et pour son bois. Elle est devenu extrêmement envahissante en Europe, Australie, Nouvelle-Zélande, Japon et en Afrique du Sud, notamment sur les berges des rivières et les bords de route. Considérée comme allélopathique (émission de substances toxiques par ses feuilles), elle est capable de se multiplier végétativement par rejets de racines (drageonnage)" (Meyer, 2008; p. 26).

Propagation:  "Seeds and also by suckering. Reproduces vigorously by root suckering and stump sprouting to form groves of trees interconnected by a common root system, and also seeds heavily every 1-2 years, with lesser amounts of seed produced in intervening years"  (Weedbusters New Zealand).

Native range:  United States, widely planted and naturalized elsewhere (GRIN).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Chile (offshore islands) Rapa Nui (Easter) Island	Rapa Nui (Easter) Island (Isla de Pasqua)	introduced invasive cultivated	Meyer, Jean-Yves (2008) (pp. 25-26, 29) "Nous avons observé une forêt dense quasi-monospécifique dans le cratère de Rano Kau avec des troncs mesurant 33 cm de diamètre à hauteur de poitrine (« diameter at breast height » ou dbh). Quelques individus sont également plantés dans le jardin botanique et arboretum de Vaitea. En absence de fruit observé, la population située dans le cratère pourrait être une population clonée s’étant propagée végétativement par drageonnage" (Meyer, 2008; p. 26).
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive cultivated	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive cultivated	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (pp. 495-496, 541-542, 557) Voucher cited: Danton D(907)770. "Los individuos presentes en RC (bosque exótico de la Falda larga) se mantienen sin mostrar, por el momento, señales marcadas de colonización. Pero el riesgo potencial de explosión de esta población no siendo despreciable, podemos pensar que seria más prudente eliminar estos individuos cuando aún es posible".

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	ILDIS Co-ordinating Centre (2013)
Australia Australia (continental)	Australia (continental)	introduced invasive cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Australia Australia (continental)	Queensland	introduced	ILDIS Co-ordinating Centre (2013)
British Columbia (province of Canada) Province of British Columbia	Canada (British Columbia)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
China China	China (People's Republic of)	introduced cultivated	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Japan Japan	Japan	introduced	ILDIS Co-ordinating Centre (2013)
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 185)
New Zealand New Zealand	New Zealand (country)	introduced invasive cultivated	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 676)
New Zealand New Zealand	New Zealand (country)	introduced invasive cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (Oregon)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (California)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (Washington)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia (Indian Ocean offshore islands) Christmas Island Group	Christmas Island	introduced cultivated	Swarbrick, J. T. (1997) (p. 126)
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Comité français de l'Union Internationale pour la Conservation de la Nature en France (2013) Naturalisée, potentiellement envahissant.

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)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013) Pennsylvania, West Virginia, Illinois, Missouri, Oklahoma, Georgia, Kentucky
United States (continental except west coast) United States (other states)	USA (Florida)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Comments:  Poisonous.  "Cultivars include forms with golden or gold-green leaves, and forms without spines, but almost all naturalised material is green-leaved and spiny"  (Webb et al., 1988; p. 676).

Control:  Control information from the Bugwood Wiki.

Physical: "Seedlings can be pulled out, however it is often difficult to tell a seedling from a new sucker (which cannot be pulled or dug out)"  (Weedbusters New Zealand).  "La coupe, l’écorçage ou le brûlage des arbres adultes employés seuls sont à proscrire car ces techniques entraînent des rejets de souches et un fort drageonnage des arbres traités" (Meyer, 2008; p. 26).

Chemical: "1. Foliar spray suckering growth and saplings 4 m tall or less. Apply glyphosate 5%, picloram or triclopyr at label rates on a 'spray-to-glisten' rather than a 'spray-to-wet' basis. Spring to early autumn.
2. Basal bark spray trees with triclopyr 20-30% (check label rate) in basal bark oil, diesel, kerosene or fuel oil (check herbicide label). Apply to wet the complete circumference of the lower 30-45 cm of the trunk to the soil level. Avoid runoff. Spring to early autumn. Can cut down trees only after death.
3. Cut and skirt with. Cut notches on downward angles around the trunk, one cut per 10 cm diameter, squirt with 1 ml of concentrated glyphosate or triclopyr (use label rate). Ensure horizontal gaps between cuts so herbicide can be carried to the roots via the phloem"  (Weedbusters New Zealand).  "Un traitement chimique par pulvérisation d’herbicide (triclopyr et/ou dicamba) sur la souche des arbres coupés ou par injection dans le tronc est possible" (Meyer, 2008; p. 26).