Like daphne (Daphne laureola) and English ivy (Hedera helix), English holly (Ilex aquifolium) is a highly invasive evergreen plant in our area. Like daphne and ivy, it grows throughout our mild winter and tolerates our dry summers well. Its preferred habitat is in moist areas within our woods, it also does well in sunnier exposed locations. In favourable sites, English holly grows rapidly into a small tree, usually less than 10 metres tall. Its branches spread out widely, and its dense, evergreen foliage blocks out light and kills native understory plants. As with other highly aggressive invasive species, it’s a good idea to remove English holly from native areas, parks and gardens. In favourable spots, the plant spreads rapidly by sending out roots that produce new shoots a bit away from the mother plant. It also spreads by having its seeds dispersed by birds that eat its fruit in the winter.
In moist areas, English holly grows rapidly into a small, wide tree that shades and outcompetes native vegetation. You can spot the tree from awhile away by it dark green shiny foliage and reaching branches. Photo credit: J Hallwort via BC Invasive Species CouncilA young specimen of English holly growing among native red alder (Alnus rubra). When first learning about our flora, people often mistake young specimens of holly for our native Oregon grapes, either the dull (Berberis nervosa), or tall (Berberis aquifolium). Note that both English holly (Ilex aquifolium) and tall Oregon grape have the species epithet (species name) ‘aquifolium’, meaning ‘wet leaf’ and referring to the shiny leaf surface. Photo credit: J Leekie via Coastal Invasive Species CommitteeThe bark of a large specimen of English holly is mottled grey with green. The small horizontal markings are lenticels – porous areas of the bark that allow for gas exchange between the living cells in under the bark and the surrounding atmosphere. Photo credit: Douglas FraserEnglish holly have simple leaves attached in a spiral pattern around the stem. The leaves are shiny due to the thick layer of cuticular waxes that waterproof the leaf and renders the plant drought tolerant. The leaf edges have very sharp, spine-like teeth. Photo credit: Douglas FraserIn the fall, English holly produces distinctive red berries that remain on the tree throughout winter. The berries are eaten by birds, who disperse the seeds to new locations – spreading the plant further into natural areas. Note the attachment of the simple leaf to the stem – compare this to the photograph of the tall Oregon grape below. Photo credit: Lynda StevensThis is the native plant tall Oregon grape – Berberis aquifolium. Sometimes, when people are first learning about our flora, they get this plant mixed up with English holly. That’s because the simple leaf of English holly, resembles a leaflet within the compound leaf of tall Oregon grape. Refer to the diagram below for a reminder of simple versus compound leaves. Look at the photos of English holly above and note how the simple leaves are attached in a spiral pattern to the main stem. Then look at how individual leaflets of tall Oregon grape are attached to a leaf stalk to form a compound leaf. The compound leaves, in turn, are attached in a spiral pattern to the stem of the tall Oregon grape plant. Photo credit: Brewbooks via FlickrThis image is a bit backlit, but it does a good job showing how the compound leaves (many leaflets attached to a leaf stalk) are attached to the main stem of the tall Oregon grape plant. Compare this to the photos of English holly leaves attached individually, directly to the stem. Photo credit: Thayne Tuason via Flickr
