Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Other Latin names:  Ligustrum walkeri Decne.

Common name(s): [more details]

Chinese: cu zhuang nu zhen

English: tree privet, wild privet

French: troéne du japon

Habit:  shrub/tree

Description:  "Shrub or small tree, twigs conspicuously white-speckled; leaves ovate to lanceolate, to 3 in. long, acute at apex and base, entire, glabrous; flowers in erect, terminal panicles 4-6 inches long" (Bailey & Bailey, 1976).

Subsp. walkeri (Decne.) P.S. Green:  "Evergreen shrub or small tree to 10 m tall.  Young stems lenticulate, glabrous or minutely puberulous.  Leaf with petiole glabrous; lamina lanceolate, glabrous, 3-9 x 1.5-2.5 cm, margin entire; base rounded or obtuse, attenuate into the petiole; apex acute-attenuate; venation somewhat obscure, 5-7 primary veins per side.  Inflorescence terminal, pyramidal, paniculate, many-flowered, scented, 7-20 cm long, glabrate or minutely puberulous.  Calyx campanulate, 1 mm long, more or less entire or with 4 very shallow triangular teeth.  Corolla tube 1 mm long, lobes 4, valvate, 2 mm long, more or less reflexed at anthesis.  Stamens 2, exserted, filament inserted at top of the corolla tube, 1.5 mm long; anthers narrowly oblong, 1 mm long.  ovary rounded, 0.5 mm; style 1.5 mm long, stigma terminal, more or less fused, elongate.  Fruit a berry, ellipsoid, 7-10 x 4-5 mm, bluish-purple when ripe"  (Dassanayake, ed., 1963; p. 271).

Subsp. chinense:  Shrubs or small trees 1-10 m, deciduous. Branchlets terete, sparsely puberulent, glabrescent. Petiole 2-8 mm, pubescent or glabrescent; leaf blade lanceolate to subovate or elliptic, 4-11 x 2-4 cm, papery, glabrous or sometimes puberulent along midrib adaxially, base broadly cuneate or subrounded, apex long acuminate; primary veins 5 or 6 on each side of midrib. Panicles terminal, 5-15 x 3-11 cm; rachis angular in fruit, puberulent. Pedicel 0-2 mm. Calyx ca. 1 mm, minutely hirsute or glabrescent. Corolla 4-5 mm; tube ca. as long as lobes. Stamens nearly reaching apex of corolla lobes; anthers 1.5-1.8 mm. Fruit black, reniform or long obovoid, 7-10(-12) x 3-6 mm, curved"  (Flora of China online).

Habitat/ecology:  Privets are extremely aggressive and can form dense, impenetrable thickets that crowd out desirable plants. They are prolific seed producers.  "[L. robustum var. walkeri] occurs up to 1,500 m in wet and intermediate low montane regions in India and in the submontane forest in Sri Lanka, at an altitude of between 725 m and 1,650 m; it often grows near streams (Lavergne et al., 1999).  "Wet and intermediate low montane regions.  Secondary montane forest, often near a stream, 450-2000 m altitude"  (Dassanayake, ed., 1963; p. 271).

Propagation:  Seed. "Fruit are injested by birds and spread in their droppings, dispersing the seeds over long distances and creating new "foci" of infestation" (Lavergne et al., 1999).  "Under shaded conditions [L. robustum var. walkeri] does not bear fruit.  The juvenile period is shortest in open areas and longest under forest canopy.  It is possible to delay sexual maturity by preserving a dense forest cover"   (Kueffer & Lavergne, 2004, p. 25).

Native range:  South-central and southeastern Asia, China (GRIN).

Presence:

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Cambodia Cambodia	Cambodia (Kingdom of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
China China	China (People's Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Indonesia Indonesia	Indonesia (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Thailand Thailand	Thailand (Kingdom of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Vietnam Vietnam	Vietnam (Socialist Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

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	MacDonald, I. A. W./Thebaud, C./Strahm, W. A./Strasberg, D. (1991) (pp. 51-61)
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Lavergne, Christophe (2006) Ligustrum robustum (Roxb.) Blume subsp. walkeri (Decne) P.S. Green, "Très envahissant". Also present: Ligustrum ovalifolium Hassk, "Cultivé/naturalisé"
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Kueffer, C./Lavergne, C. (2004) (p. 4) Ligustrum robustum subsp. walkeri
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Baret, Stephane/Rouget, Mathieu/Richardson, David M./Lavergne, Christophe/Egoh, Benis/Dupont, Joel/Strasberg, Dominique (2006) (p. 758)
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island	introduced invasive	Lorence, D./Sussman, R. W. (1988) (pp. 187-204) L. robustum var. walkeri (Decne.) Mansfr.).
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island	introduced invasive	Kueffer, C./Mauremootoo, J. (2004) (p. 6) L. robustum var. walkeri (Decne.) Mansfr.).
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Rodrigues Island	introduced invasive	Cronk, Q. C. B./Fuller, J. L. (2001) (p. 166)
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Rodrigues Island	introduced invasive	Kueffer, C./Mauremootoo, J. (2004) (p. 6) L. robustum var. walkeri (Decne.) Mansfr.).

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 invasive	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Control:  Additional information on control of Ligustrum spp. from the Bugwood Wiki.

Physical: Small plants may be hand pulled; older individuals need to be dug out.

Chemical:  For L. robustum var. walkeri in Réunion, "the most effective technique lasts for three years and is applied in natural, fairly undisturbed forests.  In the first year, seedlings are removed by hand and mature plants are cut at the base and then treated with a solution of glyphosate (Missile at 360 g/l).  Further control measures are necessary during the first two years after treatment to eliminate all regrowing plants.  The longevity of the seeds in the soil is rather short (maximum two years).  The systematic elimination of all seedlings and adults over a period of two years guarantees the total eradication of the species in a site.  Additionally, knowing that the minimum juvenile period is two years in open areas and 4-5 years under forest canopy, the control efforts need to be applied only every 2-4 years, according to light conditions"  (Kueffer & Lavergne, 2004, p. 24).

Biological: An investigation of possible biological control agents for L. robustum var. walkeri is under way on La Réunion.  "Among the 30 plant pathogen species collected, only one species, the mitosporic fungus Thedgonia ligustrina, is promising.  Twenty-one insect species were assessed and host specificity testing begin.  The epiplemid moth Epiplema albida seems to be a promising biocontrol agent.  Before releasing E. albida in Réunion, research is currently concentrating on collecting fresh E. albida material from Sri Lanka, eliminating its associated parasitoids, and then conducting complementary tests  in quarantine in Réunion"  (Kueffer & Lavergne, 2004, p. 25).

Additional information:
Report (PDF format) from US Geological Survey, Biological Resources Division, Haleakala Field Station, Hawaii "Plants of Hawaii".
Information on Ligustrum robustum from the Global Invasive Species Database.
Information on Ligustrum spp. from the Bugwood Wiki.

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

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

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

References:

Bailey, L. H./Bailey, E. Z. 1976. Hortus third: A concise dictionary of plants cultivated in the United States and Canada. Macmillan, New York. 1290 pp.

Baret, Stephane/Rouget, Mathieu/Richardson, David M./Lavergne, Christophe/Egoh, Benis/Dupont, Joel/Strasberg, Dominique. 2006. Current distribution and potential extent of the most invasive alien plant species on La Réunion (Indian Ocean, Mascarene islands). Austral Ecology (2006) 31, 747-758.

Comité français de l'Union Internationale pour la Conservation de la Nature en France. 2010. Les espéces envahissantes en outre-mer (online resource).

Cronk, Q. C. B./Fuller, J. L. 2001. Plant invaders. Earthscan Publications, Ltd., London. 241 pp.

Dassanayake, M. D., gen. ed. 1983. A revised handbook to the flora of Ceylon. Vol VI. Amerind Pub. Co., New Delhi. 424 pp.

Kueffer, C./Lavergne, C. 2004. Case studies on the status of invasive woody plant species in the western Indian Ocean. 4. R233;union. Food and Agriculture Organization of the United Nations, Forestry Department, Forest Resources Division, Forest Resources Development Service, Working Paper FBS/4-4E. 37 pp.

Kueffer, C./Mauremootoo, J. 2004. Case studies on the status of invasive woody plant species in the western Indian Ocean. 3. Mauritius (islands of Mauritius and Rodrigues). Food and Agriculture Organization of the United Nations, Forestry Department, Forest Resources Division, Forest Resources Development Service, Working Paper FBS/4-3E. 35 pp.

Lavergne, Christophe. 2006. List des especes exotiques envahissantes a La Reunion. Unpublished manuscript (Excel file). .

Lavergne, Christophe/Rameau, Jean-Claude/Figier, Jacques. 1999. The invasive woody weed Ligustrum robustum subsp. walkeri threatens native forests on La Réunion. Biological invasions: 1(4):377-392.

Lorence, D./Sussman, R. W. 1988. Diversity, density, and invasion in a Mauritian wet forest. Monogr. Syst. Bot. Missouri Bot. Garden 25:187-204.

MacDonald, I. A. W./Thebaud, C./Strahm, W. A./Strasberg, D. 1991. Effects of alien plant invasions on native vegetation remnants on La Reunion (Mascarenes Islands, Indian Ocean). Environmental Conservation 18 (1):51-61.

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.

Zhengyi, Wu/Raven, Peter H./Deyuan, Hong. 2011. Flora of China (online resource).