Grevillea robusta A.Cunn. ex R.Br., Proteaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Evaluate, score: 5 (Go to the risk assessment)

Common name(s): [more details]

English: Australian silky-oak, he oak, she-oak, silk oak, silky oak, silver oak, southern silky-oak

French: chêne d'Australie, grévillée robuste, grevillaire

Hawaiian: ha‘iku ke‘oke‘o

Japanese: shinobu-no-ki

Tongan: ‘oke

Habit:  tree

Description:  "Large evergreen tree 18-30 m high with a straight trunk and moderately spreading crown.  Leaves:  Dark green above, grayish-white or rusty-silky beneath, two-pinnatifid, deeply incised, fern-like, 150-300 mm long, leaflet margins recurved.  Flowers:  Golden-orange, stalked, 20-30 mm long, in terminal, bottlebrush-like sprays 80-150 mm long.  Fruits: Brownish-black, leathery follicles about 20 mm long, containing one or two flat, winged seeds"  (Henderson, 1995; p. 82).

Habitat/ecology:  This large, evergreen tree has been used extensively in reforestation programs. The leaves produce an allelopathic substance that inhibits the establishment of all species, including itself apparently.  It grows well in dry areas between 350-1,600 m (Smith, 1985; p. 191). "Widely planted and a prolific seeder, it is a weed of drier mesic pastures and forests.  Pollen may trigger hay fever"  (Motooka et al., 2003).  In New Caledonia, "arbre planté assez commun à Nouméa et dans l'intérieur" (MacKee, 1994; p. 119).

Propagation:  Wind-dispersed seeds.

Native range:  New South Wales and Queensland, Australia; 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
Australia (Pacific offshore islands) Lord Howe Island	Lord Howe Island	introduced	Pickard, J. (1984) (p. 207)
Australia (Pacific offshore islands) Lord Howe Island	Lord Howe Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 20) "Frequently planted as a timber tree throughout tropical and subtropical regions, and often becoming naturalised". Voucher cited: A.C. Beauglehole 5509 (MEL)
Australia (Pacific offshore islands) Norfolk Islands	Norfolk Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 10) "Frequently planted as a timber tree throughout tropical and subtropical regions, and often becoming naturalised". Voucher cited: W.R. Sykes NI 514 (CHR)
Chile (offshore islands) Rapa Nui (Easter) Island	Rapa Nui (Easter) Island (Isla de Pasqua)	introduced cultivated	Meyer, Jean-Yves (2008) (pp. 40, 42) "Nous l’avons vu communément planté autour des zones de pâturages mais sans régénération naturelle visible" (Meyer, 2008; p. 40).
Cook Islands Southern Cook Islands	‘Atiu Island	cultivated	McCormack, Gerald (2013) Uncommon.
Cook Islands Southern Cook Islands	Mangaia Island	cultivated	McCormack, Gerald (2013) Uncommon.
Ecuador (Galápagos Islands) San Cristóbal Group	San Cristóbal Island	introduced cultivated	Charles Darwin Foundation (2008)
French Polynesia Marquesas Islands	Nuku Hiva (Nukahiva) Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Naturalisée
French Polynesia Marquesas Islands	Ua Huka (Huahuna, Uahuka) Island	introduced cultivated	Lorence, David H./Wagner, Warren L. (2013)
French Polynesia Marquesas Islands	Ua Huka (Huahuna, Uahuka) Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (2003) (voucher ID: PTBG 40877) Taxon name on voucher: Grevillea robusta
French Polynesia Society Islands	Raiatea (Havai) Island	introduced	Fosberg, F. R. (1997) (p. 126)
French Polynesia Society Islands	Taha‘a Island	introduced	Fosberg, F. R. (1997) (p. 126)
French Polynesia Society Islands	Tahiti Island	introduced cultivated	Welsh, S. L. (1998) (p. 224) Voucher cited: Florence 2448
French Polynesia Society Islands	Tahiti Island	introduced invasive cultivated	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Voucher cited: J. Florence 2448 (PAP) Naturalisée
French Polynesia Tuamotu Archipelago	Makatea (Ma‘atea) Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Naturalisée
French Polynesia Austral (Tubuai) Islands	Rapa Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Naturalisée
French Polynesia Austral (Tubuai) Islands	Rurutu Island	introduced	Meyer, Jean-Yves (2000) (p. 94) "Potential invader".
French Polynesia Austral (Tubuai) Islands	Rurutu Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Naturalisée
Guam Guam Island	Guam Island	introduced cultivated	Stone, Benjamin C. (1970) (pp. 259-260) Voucher cited: Stone 4092 (GUAM)
Guam Guam Island	Guam Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 63)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1086)
State of Hawaii Hawaiian Islands	Hawaiian Islands	invasive	Moodley, Desika (2013) (p. 124) accessed 20180711, "Invasive in South Africa [7,8], Hawaii, Brazil, Uganda and Guatemala [8], Reunion island [9], and many pacific islands [5]"
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive	Starr, Forest/Starr, Kim/Loope, Lloyd L. (2006) (p. 40) Single seedling seen and pulled. Voucher cited: Starr, Starr, Higashino & Bruch 040607-1 (BISH)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1086)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive cultivated	Herbarium Pacificum Staff (1999) (p. 8) Voucher cited: C. Imada, H. Oppenheimer, J.S. Meidell & C. Gemmill 98-7 (BISH)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1086)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive cultivated	Oppenheimer, Hank L. (2003) (p. 22) Voucher cited: Oppenheimer H110129 (BISH, PTBG)
State of Hawaii Hawaiian Islands	Ni‘ihau Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1086)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1086)
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced cultivated	MacKee, H. S. (1994) (p. 119) Vouchers cited: Cribs 1300, Le Rat 222, Sarlin 57, MacKee 29471
Niue Niue	Niue Island	introduced cultivated	Sykes, W. R. (1970) (p. 172) Single tree. Voucher cited: CHR 168710
Niue Niue	Niue Island	introduced cultivated	Space, James C./Flynn, Tim (2000) (p. 24)
Pacific Pacific	Pacific islands	invasive	Moodley, Desika (2013) (p. 124) accessed 20180711, "Invasive in South Africa [7,8], Hawaii, Brazil, Uganda and Guatemala [8], Reunion island [9], and many pacific islands [5]"
Samoa Western Samoa Islands	Upolu Island	introduced cultivated	Space, James C./Flynn, Tim (2002) (p. 9) Planted tree at watershed nursery, Vailima.
Solomon Islands Solomon Islands	Solomon Islands	introduced cultivated	Hancock, I. R./Henderson, C. P. (1988) (p. 79)
Tonga Tongatapu Group	‘Eua Island	introduced cultivated	Space, James C./Flynn, Tim (2001) (p. 7)
Tonga Tongatapu Group	Tongatapu Island	introduced cultivated	Space, James C./Flynn, Tim (2001) (p. 7)
Tonga Vava‘u Group	Vava‘u Island	introduced cultivated	Space, James C./Flynn, Tim (2001) (p. 7)

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	native	Australian Biological Resources Study (2013)
Australia Australia (continental)	Queensland	native	Australian Biological Resources Study (2013)
Central America Central America (Pacific rim)	Guatemala (Republic of)	invasive	Moodley, Desika (2013) (p. 124) accessed 20180711, "Invasive in South Africa [7,8], Hawaii, Brazil, Uganda and Guatemala [8], Reunion island [9], and many pacific islands [5]"
China China	Hong Kong	introduced cultivated	Wu, Te-lin (2001) (p. 157) Ornamental.
New Zealand New Zealand	New Zealand (country)	introduced invasive cultivated	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 997) "Rough pasture on scoria of volcanic cone".
Singapore Singapore	Singapore (Republic of)	introduced cultivated	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 46) Cultivated only

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. 115)
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive cultivated	Comité français de l'Union Internationale pour la Conservation de la Nature en France (2013) Utilisé pour la foresterie et planté comme plante ornementale; envahissant principalement dans les milieux perturbés.
La Réunion (France) La Réunion Island	La Réunion Island	invasive	Moodley, Desika (2013) (p. 124) accessed 20180711, "Invasive in South Africa [7,8], Hawaii, Brazil, Uganda and Guatemala [8], Reunion island [9], and many pacific islands [5]"
French Territory of Mayotte Mayotte Islands	Mayotte Island	introduced cultivated	Comité français de l'Union Internationale pour la Conservation de la Nature en France (2013) Potentiellement envahissant.
Seychelles Seychelles Islands	Seychelles Islands	introduced	Invasive Species Specialist Group (2017)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Africa Africa	Uganda	invasive	Moodley, Desika (2013) (p. 124) accessed 20180711, "Invasive in South Africa [7,8], Hawaii, Brazil, Uganda and Guatemala [8], Reunion island [9], and many pacific islands [5]"
South Africa South Africa	South Africa (Republic of)	invasive	Moodley, Desika (2013) (p. 124) accessed 20180711, "Invasive in South Africa [7,8], Hawaii, Brazil, Uganda and Guatemala [8], Reunion island [9], and many pacific islands [5]"
South America (non-Pacific rim) South America (non-Pacific rim)	Brazil	invasive	Moodley, Desika (2013) (p. 124) accessed 20180711, "Invasive in South Africa [7,8], Hawaii, Brazil, Uganda and Guatemala [8], Reunion island [9], and many pacific islands [5]"

Comments:  This tree is sometimes used in forestry plantings. It is naturalized in Hawai‘i. Where not present, it should probably not be introduced. New plantings should be limited and existing plantings monitored for invasive behavior.

Naturalized and starting to spread on the island of Rurutu (Austral archipelago, French Polynesia) (Jean-Yves Meyer, pers. com.).

Single tree noted at the watershed nursery in Vailima, Upolu, Samoa (Space & Flynn, 2002).

Control: 

Physical: "Has value as timber. Goats will control silver oak (An Peischel)" (Motooka et al., 2003).

Chemical: "Sensitive to triclopyr ester (2.5% product in diesel oil) applied to frill cuts.  HAVO staff reported control with triclopyr ester at 5% product in diesel oil applied to basal bark (Zimmer, HAVO).  Susceptible to cut-surface and continuous frill applications of picloram and glyphosate and tolerant of 2,4-D and dicamba. Applications of glyphosate and triclopyr to drilled holes in unreplicated demonstrations were very effective" (Motooka et al., 2003).