Ilex aquifolium is an evergreen flowering shrub or tree. It was native to Eurasia and northern Africa but was intentionally introduced to the Pacific Northwest as an ornamental plant in 1869 (Olmsted 2006, cited in Boersma et al. 2006). The berries and shiny leaves of English holly are recognized by many as a winter decoration (Klinkenberg 2017).
Description:
I. aquifolium can develop multiple stems (shrub-like) or grow a single stem (tree-like) up to 18 m tall and live for 300 years (SSISC 2017). The oval leaves are leathery and dark green. Young plants have leaves with sharp, stout spines along the margins, which may alternately point up and down. Older plants typically have smooth leaves (Klinkenberg 2017). The bright red berries that form are in sharp contrast to the green leaves.
Ecology:
English holly can be found in forested sites and along the edges of wetlands in the southwestern portion of the province (Invasive Species Council of British Columbia 2017, Klinkenberg 2017). It is tolerant of a wide range of light conditions, including deep shade (Klinkenberg 2017). However, seedlings require moist soils, which somewhat limits their distribution (Peterken 1966). Where English holly has established, there is concern that it suppresses the germination and growth of more light sensitive species and could out-compete native species for water and nutrients (Invasive Species Council of British Columbia 2017; SSISC 2017).
Reproduction and Dispersal:
Holly shrubs will have either small white female flowers or male flowers that produce pollen. Following the pollination of the female reproductive structures in the flowers, fertilization occurs and seeds are produced. The seeds are embedded in the round red berries that become evident on the female plants in the late fall and winter (SSISC 2017). These berries are eaten by birds (e.g. robins) and small mammals, which disperse the seeds (Peterken 1966; Zika 2010). Although attractive, these berries are mildly toxic to people and should not be consumed (SSISC 2017).
References cited:
Invasive Species Council of British Columbia. 2017. English holly. [accessed 2017 January 27]. http://bcinvasives.ca/invasive-species/identify/invasive-plants/english-holly.
Klinkenberg B, editor. 2017. E-Flora BC: Electronic Atlas of the plants of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [accessed 2018 Jan 29]. http://linnet.geog.ubc.ca/Atlas/Atlas.aspx?sciname=Ilex%20aquifolium.
Olmsted D. 2006. English Holly. In: Boersma PD, Reichard SH, Van Buren AM, editors. Invasive Species in the Northwest. Seattle: University of Washington Press.
Peterken GF. 1966. Mortality of holly (Ilex aquifolium) seedlings in relation to natural regeneration in the new forest. Journal of Ecology. 54(1):259–269.
[SSISC] Sea to Sky Invasive Species Council. 2017. English holly. [accessed 2017 Jan 27]. http://www.ssisc.info/home/english_holly.
Stokes DL, Church ED, Cronkright DM, Lopez S. 2014. Pictures of an invasion: English holly (Ilex aquifolium) in a semi-natural Pacific Northwest forest. Northwest Science. 88(2):75–93.
Zika PF. 2010. Invasive hollies (Ilex, Aquifoliaceae) and their dispersers in the Pacific Northwest. Madroño. 57(1):1–10.
Klinkenberg B, editor. 2017. E-Flora BC: Electronic Atlas of the plants of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [accessed 2018 Jan 29]. http://linnet.geog.ubc.ca/Atlas/Atlas.aspx?sciname=Ilex%20aquifolium.
Olmsted D. 2006. English Holly. In: Boersma PD, Reichard SH, Van Buren AM, editors. Invasive Species in the Northwest. Seattle: University of Washington Press.
Peterken GF. 1966. Mortality of holly (Ilex aquifolium) seedlings in relation to natural regeneration in the new forest. Journal of Ecology. 54(1):259–269.
[SSISC] Sea to Sky Invasive Species Council. 2017. English holly. [accessed 2017 Jan 27]. http://www.ssisc.info/home/english_holly.
Stokes DL, Church ED, Cronkright DM, Lopez S. 2014. Pictures of an invasion: English holly (Ilex aquifolium) in a semi-natural Pacific Northwest forest. Northwest Science. 88(2):75–93.
Zika PF. 2010. Invasive hollies (Ilex, Aquifoliaceae) and their dispersers in the Pacific Northwest. Madroño. 57(1):1–10.