As you hunker down next to your fireplace during these bone-chilling days, you may feel in the festive mood and be listening to Christmas carols, including traditional pieces such as ‘Deck the Halls with Boughs of Holly’ and ‘The Holly and the Ivy’. But wait. Holly and ivy? Aren’t these invasive plants?
The green and red colours of holly and ivy are traditionally associated with Christmas, and decorating homes with wreaths of fir and cedar boughs, and sprigs of holly, ivy and mistletoe, are age-old Christmas customs.
English holly with its shiny green, prickly leaves and clusters of red berries is especially symbolic of the holidays.
Holly is a large, evergreen shrub that can grow to the height of a small tree, up to 13 metres. Holly bark is smooth and grey, and the wood is white and hard with a very even grain. Valued by wood turners, it has been used for inlay work, chess pieces and black piano keys.
Originally from Eurasia and northern Africa, English holly was introduced to North America as an ornamental shrub. It prefers mild winters, and thrives in many locations throughout the Pacific Northwest.
It is particularly a problem in North Vancouver and on portions of Vancouver Island where it has escaped from urban gardens and spread into woodlands and parks. Given a foothold, holly can dominate the tall shrub layer, creating a deep shade difficult for some native species to grow in.
While English holly does grow in our region, I do not anticipate it to ever become the problem that it presents in coastal regions of our province.
However, as with so many other ornamental plants that are potentially invasive, it’s important to consider where you live and whether your property borders a natural park where holly could get a foothold. And while it’s unquestionably an attractive plant, I would strongly encourage the planting of alternate species whenever possible.
Consider other varieties of holly that are not considered invasive or better yet, plant Oregon-grape, an equally beautiful native plant that produces clusters of showy yellow flowers in the spring, followed by blue berries in the late summer. If you do chose to grow English holly, consider cutting off the dead flowers, seedpods and berries to reduce the opportunities for this plant to spread.
English ivy has also become a major invader in the Pacific Northwest, from B.C. to California. It is a widely planted evergreen vine, introduced as an ornamental into North America from Eurasia during colonial times. This amazing vine can reach heights of 50 meters and depths of 1 metre above ground.
Similar to holly, English ivy suppresses and excludes other vegetation to form a dense monoculture groundcover. As a vine, it can completely engulf shrubs and encircle tree trunks of all sizes, leaving nothing uncovered.
Shrubs shrouded in ivy may eventually die because light can’t reach their leaves. The sheer weight of the extra vegetation also weakens the plant it grows on, making it more susceptible to disease and blowdown. I was shocked to discover there are more than 400 cultivars of this type of ivy grown in home gardens.
Due to ivy’s holiday symbolism and its prevalence in our region, I should not have been surprised to see it being used in Christmas wreaths at a recent workshop I attend. But I was.
However, I have to admit that it can be quite attractive when woven onto a decorative wreath. I saw this as an opportunity to educate the other workshop participants about the impacts of invasive plants on our landscapes and the importance of proper disposal.
Similar to disposing of your planters and hanging baskets in the fall, improper disposal of living wreaths can result in undesirable ornamental plants moving into natural areas or parks adjacent to your property. English ivy and many other plants can re-sprout from their roots or stems.
For anyone battling English ivy on your properties, small infestations can be manually pulled, dug out or cut back. As noted, the plants will re-sprout from roots and stem fragments but repeated pulling can eventually result in success. Pieces of the cut vines may re-sprout if left lying on the soil, so take care to remove all or as much of the plant fragments as possible from the site. Mowing may work as a control, but needs to be repeated several times during each growing season.
For information on invasive species go to our website: www.oasiss.ca or contact the Program Coordinator for the Okanagan-Similkameen, Lisa Scott, at 250-404-0115.