Got invaders in your backyard? Torrey Archer, Covenant Manager at The Land Conservancy of BC, says that while English ivy and periwinkle can be beautiful backyard plants, these species can strangle and shade out the life around them – including Oak Bay gardens and fragile Garry Oak ecosystems.
“English ivy is gorgeous. It has a very fanciful look to it. It grows up over everything,” says Archer. She suggests that on rock walls, this growth may not be so damaging, but the climbing plant is prone to strangling other native plants, garden plants and trees.
Trees climbed by English ivy pose the highest risk to homeowners. “The ivy’s roots will grow into the bark, and this creates infection sites for pests and pathogens. The tree will eventually become strangled by it,” Archer says. Because trees rely on their trunks to carry water and nutrients, the strangulating ivy cuts off the tree’s circulatory system. “If you have trees hanging over your house and you have all this ivy on it, it looks beautiful, but it’s actually in danger of falling on your house.” Archer recommends always checking with an arborist about trees covered in ivy, but removing the invasive plant is the best course of action.
“When you do remove ivy from a tree, it’s called the life-saver method,” Archer says, simply because the removal ring created resembles a life-saver candy. “You clip the ivy a couple of feet above the soil, on the tree trunk itself.” Remove only one to two feet of the ivy, clearing a ring around the tree that is free of the vine. “From there, don’t pull the ivy off the bark. You’ll either pull bark off as well, or open up those sites for more infection,” Archer warns. Leave the ivy on the tree and everything above the ring will wither.
As for the vine still alive at ground level, Archer suggests hacking it to the ground. “For ground removal, you can pull it out with your hands because there are no spikes or thorns. It’s also very satisfying, because you’ll see a real difference after you’ve worked for just an hour.”
English ivy is a persistent problem because, despite human intervention, birds eat the berries and disperse the seeds in nearby areas. Archer says, “You have to not hope for immediate success. It’s on ongoing battle. Pick away at it year after year because it’s worthwhile.”
A horizontal lookalike of English Ivy, periwinkle is a ground cover that doesn’t reach more than four to six inches in height, but presents similar suffocating risks. The colour periwinkle was named after the plant, which blossoms in flowers of the same light violet-blue.
“The problem with periwinkle is that, like ivy, it’s often sold in stores,” Archer says. “It will displace anything in its way.”
Many gardeners become frustrated with periwinkle because of its fast-travelling tendencies, which prompts them to pull up the plant and throw it in the compost. Archer warns against this, as the compost becomes “an invasive species dispersal vector.” The same goes for dumping the plant roadside. “Out in Sooke, someone dumped periwinkle on the side of the road and it went through the ditch, up into the forest and now it’s blanketed 45 square meters of forest. It’s making its way down the hill to the creek,” Archer says. Once at the creek edge, periwinkle forms a dense mat of roots above ground rather than below, contributing to soil erosion. With soil erosion comes turbid creek water, which is inhabitable for fish.
“It’s all these cascading effects you wouldn’t even think of from this pretty little plant,” Archer says.
Those who have planted rhododendrons in their own gardens, but don’t remember planting a rhododendron in a certain area, are likely dealing with an invasion of daphne laurel.
One way to recognize the plant is by its single stem, different than the rhododendron spray. Another way is by its pungent and toxic gas, which can be a serious health risk for people and pets. “Some people even get blisters from the juices,” Archer says. When pulling the plant for removal, wear gloves. Archer adds, “If you’re removing a bunch of it, do not transport it to a landfill in a closed car, because those noxious fumes are not good for you.” Wrap the plant in plastic bags and close it in the trunk before driving.
Other invasive species to look out for include:
False lamium, also known as yellow archangel
Giant hogweed, also known as cow parsnip
St. John’s wort
Yellow flag iris
Torrey Archer and volunteers with The Land Conservancy of BC remove invasive species from covenants, roadsides and parks.