Ilex aquifolium L., Aquifoliaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  yes

Risk assessment results:  High risk, score: 17 (Go to the risk assessment)

Common name(s): [more details]

English: English holly, European holly

Spanish: muerdago

Habit:  tree

Description:  "Evergreen shrubs or small trees 2-10 m tall.  Leaves dark green, thick, glossy, ovate or elliptic, 5-12 cm long, 2.5-5.5 cm wide, glabrous, margins usually thickened, undulate, regularly or irregularly toothed, the teeth stiff, spreading, spinose, rarely entire.  Flowers fragrant, in fasiculate cymes along previous year's growth, up to ca. 1 cm long, peduncles 0.3-0.5 cm long; calyx lobes 4, deltate, ca. 1.5-2 mm long; corolla lobes ca. 4 mm long; ovary 4-celled.  Fruit bright red, 8-10 mm in diameter" (Wagner et al., 1999; pp. 222, 224).

Habitat/ecology:  "Forests, forest edges, scrub- and woodland.  In the native range, the plant occurs in woods, hedges and scrub.  Numerous cultivars and hybrids have been developed.  The plant forms dense thickets on the floor and on trees that change the structure of invaded forests by adding a tall and species-poor shrub layer.  Native plants are impeded in their growth and regeneration"  (Weber, 2003; p. 212).  "Dominates the tall shrub layer in moist, nutrient-rich sheltered bushland, creating deep shade in which native species can neither grow nor germinate, changing the environment"  (Weeds of Blue Mountains bushland).  Prefers acid, sandy or gravelly loam soils (Csurhes & Edwards, 1998; p. 111).

In Hawai‘i, "occasionally cultivated and now naturalized at the edge of degraded wet forest, 1,860 m" (Wagner et al., 1999; pp. 222, 224).

Propagation:  Seed, spread by birds (Wagner et al., 1999; pp. 222, 224).  "Holly also spreads by suckering and layering"  (Weeds of Blue Mountains bushland).

Native range:  "Southern and western Europe, northern Africa, and western Asia, widely cultivated" (Wagner et al., 1999; pp. 222, 224).

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) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive cultivated	Atkinson, Rachel/Sawyer, John (2011)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 222, 224) Voucher cited: Herbst 8846 (BISH)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R. (1995) (p. 15) East Maui. Voucher cited: Tanabe 37 (BISH)
Nauru Nauru Island	Nauru Island	introduced cultivated	Thaman, R. R./Fosberg, F. R./Manner, H. I./Hassall, D. C. (1994) (p. 94) Ilex sp.; voucher cited: Hassall 164 (SUVA)

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)	Australia (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Australia Australia (continental)	New South Wales	introduced invasive	Csurhes, S./Edwards, R. (1998) (p. 111) Also Tasmania, South Australia and Victoria.
New Zealand New Zealand	New Zealand (country)	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 143) "Scrubland and forest".

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: 

Physical:  "Small plants and seedlings are pulled or dug out, the roots must be removed".

Chemical:  "Freshly cut stumps should be treated with  glyphosate herbicide, otherwise the species will resprout.  Fruit-bearing plants should be removed first to prevent seed dispersal"  (Weber, 2003; p. 212).

"1. Swab stumps (all year round): cut down and paint freshly cut stumps with glyphosate (200ml/L) or Tordon Brushkiller (200ml/L). Dispose of cut material at refuse transfer station.
2. Bore and fill (spring-summer)): 1 downward angled hole every 5-10 cm around the trunk, 1.5 ml per hole Tordon Brushkiller (undiluted).
3. Frilling (all year round): With a sharp chisel or axe, make a deep cut into the sapwood at 5 cm intervals around the base of the tree, taking care not to ring-bark the plant. Immediately saturate the cuts with 1.5 ml of Tordon BK (undiluted) or glyphosate (200ml/L)"  (Weedbusters New Zealand).

Additional information:
Information and photos at Weeds of Blue Mountains bushland.
Information sheet from Weedbusters New Zealand.

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

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

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

References:

Atkinson, Rachel/Sawyer, John. 2011. Naturalized species in the Juan Fernández Archipelago, Chile. Unpublished spreadsheet.

Csurhes, S./Edwards, R. 1998. Potential environmental weeds in Australia: Candidate species for preventative control. Canberra, Australia. Biodiversity Group, Environment Australia. 208 pp.

Harley, Barbara. 2009. Weeds of Blue Mountains bushland. (online resource).

Staples, George W./Herbst, Derral/Imada, Clyde T. 2000. Survey of invasive or potentially invasive cultivated plants in Hawai‘i. Bishop Museum Occasional Papers No. 65. 35 pp.

Thaman, R. R./Fosberg, F. R./Manner, H. I./Hassall, D. C. 1994. The flora of Nauru. Smithsonian Institution, Washington. Atoll Research Bulletin 392:1-223.

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

Wagner, Warren L./Herbst, Derral R. 1995. Contributions to the Flora of Hawai‘i. IV. New Records and name changes. In: Evenhuis, Neal L. and Miller, Scott, E., eds. Records of the Hawaii Biological Survey for 1994. Part 2: Notes. Bishop Museum Occasional Papers. 42:13-27.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. 1988. Flora of New Zealand, Volume IV: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.