Alien Invaders: Losing the battle with invasive species

Awareness is everything when dealing with the spread of invasive species

This is a warning: Not everything green is good. There lurk among us, in growing numbers, alien species: escapees from the halfway house of someone’s backyard, leafy temptations scored from some garden shop as a quick fix for a bare patch of ground, unwanted herbaceous pests arriving unseen in the Trojan horse of a sack of imported grain.

Their invasion has been assisted by the wind, by birds spreading their seed, or worse, by gardeners dumping cuttings at the edge of public parkland. For more than you ever want to know about invasive species, just ask Andrew Appleton, or better yet, join him, as I did, on a visit to Jericho Park on Vancouver’s West Side.

What to look out for: Invasive species

Appleton works for Evergreen, a non-profit outfit, and sits on the board of the Greater Vancouver Invasive Plant Council, a group including government officials and conservationists like himself.

At one trailhead leading into Jericho, he points out “a fiesta” of invasive species: periwinkle, laurel, holly, Himalayan blackberry and ivy.

Farther along the trail there is a massive patch of Japanese knotweed or false bamboo. It grows from zero to 10 feet every season. Its root system is as deep as the plant is high. A sliver a few centimeters long will sprout roots and quickly develop into a full-grown plant. Like many invasive species, it is so dense that nothing can grow beneath it; no seeds of native plants can germinate.

Giving the native plants a chance

Nearby the knotweed are small native conifers recently planted by volunteers assembled by Appleton through Evergreen. The young plants are already struggling under a veil of morning glory, another invader.

Scotch broom, which is not present here but has infested other parks in the area, has the same effect on the ability of seedlings to germinate. It is also toxic to livestock.

The ivy is a double threat. It covers the ground and muscles native ground cover out of the way. But it also grows up trees, attached by tendrils that pierce the bark and provide access to diseases. And finally, as it moves toward the crown of the plant, it adds so much weight the host frequently snaps in the first strong wind.

Of course most of what we grow in B.C. is alien. But most species manage to coexist with the natives. Appleton says it can take

Some that were once considered beneficial in fact can become a serious problem. Consider purple loosestrife. It was introduced in the 19th century because it was attractive as a medicinal herb. It was used for treatment of diarrhea, dysentery, bleeding, wounds, ulcers and sores. Today it is one of North America’s most wanted enemies; it has degraded many wetlands in North America as it proliferates, sucks up water and crowds out what was there before.

Holly, that plant so often associated with Christmas, a season for giving, is a taker in the forest, a real “water hog” Appleton calls it. There are whole stretches in Pacific Spirit Park where holly is the dominant tree, replacing fir and cedar.

That kind of conquest throws the entire relationship of native plants and animals that has evolved together over millennia out of whack. And trying to regain the ground lost to the invaders, Appleton would admit, is not a struggle we are winning. At best we are stopping further advances.
Once a month, volunteers supported by Vancouver Park Board staff gather at Jericho to rip out ivy and holly and blackberries. And volunteers haul out tonnes of the same stuff each year from Stanley Park, VanDusen and what was once Vancouver’s main landfill but is now Everett Crowley Park.

Meanwhile at Iona, out near the airport, corporate groups have volunteered to remove broom plants.

This battle has been going on in some Vancouver locations for decades, but it is nowhere nearly as well funded here as in jurisdictions such as Seattle, which a few years ago committed millions at $300,000 a year to this cause. Nor are we as determined as Oregon, where it is illegal to sell or propagate several species of ivy.

As the battle continues, you can do your part

Check the Greater Vancouver Invasive Plant Council website for a list of invasive species that may be green and may be beautiful but are definitely not good to plant.

Allen Garr is a Vancouver journalist with a passion for birding and beekeeping. Read past columns by Allen Garr.