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Powell River Garden Club: Invasive species, part one

"Our property of almost an acre boasts masses of plants, a mix of native, non-native and, I now realize, invasive as well." ~ Lesley Moseley
SCHIEFFELIN’S STARLINGS: European starlings imported by a New York resident and released in the city’s Central Park in the late 1800s made their way west.

I spent my childhood years on Lulu Island (which sounds so much more romantic than Richmond). Connected by bridges to Vancouver, this island is a gift of the Fraser River with its rich delta soil that delighted my mother, an avid gardener.

Our property was bordered by miles of commercial blueberry fields introduced in the 1920s. They thrived in the rich peat bogs that made up much of the island. We spent our summers picking blueberries, the source of income for many kids at the time. In the mid 60s, the blueberry harvest was drastically reduced by what was my first introduction to an invasive species, the European starling.

I remember the vast swarms of these birds. As far as one could see, the power lines were covered with them. Farmers despaired of the invaders. I remember hearing that a 25-cent bounty was offered for a pair of starling feet. Anyone within earshot of the blueberry fields despaired of the continual cannon fire occurring day and night to scare off the rapacious pillagers.

At the time, a rumour circulated that a Japanese couple had brought a pair of starlings with them when they immigrated to Canada, then released them. But where had they really come from?

In 1890, New Yorker Eugene Schieffelin imported 60 European starlings from Europe and released them into Central Park. He had previously imported nightingales and skylarks, but they had not survived. But starlings thrived and began to migrate west.

The first starlings arrived in 1945 to the Pacific coast. The numbers peaked in 1966 and then strangely began a sharp, dramatic decline. The numbers have now stabilized, however, starlings continue to pose a threat to native bird species, outcompeting them in nesting sites and destroying other birds’ eggs.

We are now aware of invasive fish, animal, bird and plant species and the potential damage they can cause to the environment. How did they get here and why are they of concern?

Non-native plants

Beginning more than a century ago, non-native plants and flowers from around the world have found their way into our gardens. Most species were deliberately introduced, others incidentally, unknowingly transported along with people and goods. When does an introduced, non-native plant become considered invasive? 

Canada’s Invasive Species Centre defines invasive species as those which “possess the ability to outcompete and overwhelm native species in its introduced range.”

Gardeners’ primary concern is invasive insect and plant species, plants that we consider weeds, and plants which have become difficult to control. English ivy (brought from Europe by settlers to Virginia, 1800), bindweed (European settlers inadvertently brought seeds along with wheat seed in the 1870s to the US), and Himalayan blackberry (introduced as a berry crop from Armenia and Iran) come to mind.

Dandelion (believed to have been brought on the Mayflower for medicinal purposes and introduced to Canada by French colonists centuries ago), although widespread, is not considered invasive in our location as it does not overwhelm native species. Its name derives from the French dente de lion, “lion’s tooth.” These four plants are the most readily identifiable invasives, but they are just the tip of the iceberg.

How do invasive plants get into our gardens? Plants that seem innocuous are purchased from suppliers, only to find out later their world-dominating intentions. Seeds can be transported along with manure, garden soils, other plants, birds or wind-borne. Our property of almost an acre boasts masses of plants, a mix of native, non-native and, I now realize, invasive as well.

I dug up pots of a lovely, ground-cover plant with variegated green and white leaves to donate to Powell River Garden Club’s plant sale. I had no idea what kind of plant it was. You’d have thought I had brought garlic bread to a vampires’ potluck! The plants were identified as goutweed, an invasive species introduced from Eurasia’s boreal forests and imported here as a groundcover. I humbly took back my rejected weed, embarrassed that I might have been instrumental in expanding its horizons over the entire district.

A couple of years ago, I purchased a cinnamon (Chinese) yam, a beautiful vine, from Richters Herbs in Ontario. Shortly after I planted it, I received an email from Richters asking me to destroy the plant as it had been deemed invasive. I was happy to receive the credit they applied to my account—the plant had died. But to make sure it no longer posed a threat I dug up and burned what was left of it.

The invasives list changes as adverse effects of introduced non-native plants become apparent. Once classified, avoiding them is crucial to protecting the health of the local environment. Japanese knotweed is an example of a plant whose disastrous effects on the environment were realized after it had become well established here as an ornamental and is monumentally difficult to eradicate. “Cut Broom in Bloom” has become a familiar local battle cry to destroy this plant that crowds out native plants in open areas. Scotch broom was intentionally introduced in 1850 as an ornamental on Vancouver Island.

Thyme time

Garden club member Lin Morrison tells a story of how she bought a thyme plant from someone. In the pot there was also another little plant that Lin didn’t recognize but planted it along with the thyme. After 10 years, she realized it was Campanula Rapunculoides, a plant that is native to Siberia. Due to its desirable attributes—an easy to grow, hardy garden plant, some of the first European settlers brought it over to North America. Those attributes have enabled it to escape cultivation and spread throughout North and South America, New Zealand and Australia.

“It was growing much more vigorously in other people's gardens than in the herb bed in front of my house,” said Lin. “I left it there undisturbed but dug out a section of nearby chives to move into the rich vegetable garden soil. Before replanting, the chives were scrupulously cleaned of every scrap of Campanula root, or so I thought. Before I knew it the Campanula was thriving in the vegetable garden. And it spread to another part of the garden, then it piggybacked onto a peony when it was moved, and so on.”

Over the years Lin has hacked it, dug it, cleaned her tools after working in the occupied territories, disposed of stems, roots and leaves like a virulent plague. Still, it persisted. Campanula Rapunculoides spreads by seed and by long fine roots which are capable of starting colonies from one tiny broken bit. When established, it produces a white carrot-like tuber that can be hard to pull.

“My one success in removing this Campanula was in the new rose garden,” added Lin. “I surely did not want to contend with it among prized perennials. There was, inevitably, a patch of this weed. Actually, there were several. I dug and screened the afflicted areas through two sizes of mesh into a wheelbarrow, picking out roots and pouring the rock into buckets full of water to wash out any tiny root scraps.

“Each barrow load was then sieved through a fine mesh riddle. Two years later, my garden is now still clear of the weed.”

Unfortunately, Lin’s war with invasives is not over.

“I thought this was my nemesis, until horsetail was introduced in a load of manure,” she laments.

Stay tuned for part two of this article from Lesley Mosely, president of Powell River Garden Club, which publishes on Sunday, March 31.

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