Gardeners beware

By Trudy Duivenvoorden Mitic, May 2013

Keeping the bullies out of your garden helps protect local parks too.

After a few years of procrastination we’ve finally tackled a dreaded job in the garden, that of digging a deep trench and installing a root barrier between our vegetable patch and a neighbour’s cedar hedge. We knew the hedge was siphoning food and water away from anaemic vegetable plants and stunted strawberries—we just didn’t know to what extent. What a creepy surprise to find the invading roots everywhere, a vast and tenacious network of tentacles lurking just below the food crop.

While chipping away in the trench with my crowbar, shovel and various pruning tools, I had plenty of time to meditate on the many invasive species that have been haplessly spread around town and are often still for sale at the local nurseries. I admit to planting some in my own garden, naive as I was at that time and impatient to transform a bare yard into a lush green space. Now I do the penance on my hands and knees, routinely yanking out another flush of periwinkle, lily-of-the-valley, sweet woodruff, Japanese anemone, goutweed and two aggressive varieties of cranesbill geranium.

They all looked so sweet and innocent in their little pots at one time. But once let loose, they began running all over the place and rapidly lost their attractiveness. Soon the lily-of- the-valley was pushing up its shoots everywhere. The periwinkle forgot about flowering and started pumping out enough greenery to choke everything in its path.

The beautifully scented sweet woodruff has shown an especially sinister side: It’s insinuated itself around a rose bush that attacks me every time I reach in to break some of the stranglehold.

Over by the shed it may look as if I’ve finally eradicated the goutweed but I’m not gullible enough to let my guard down. All of these pests are groundcovers that spread via runners, both above and below ground. I know they’ll never be completely gone.

But I also know I can keep them confined to my garden, which, unfortunately, is not the case with a more notorious non-native species, English ivy. This graceful vine with its heart-shaped leaf is hardy and lush and stays green in winter, so its enduring attraction is understandable. It also quickly fills a planter and beautifies the most challenging corner in the garden. On the other hand, it’s so insidiously adaptable that in your neighbourhood you’re apt to find both a young specimen potted up in a lovely planter box and an old one bringing down a stately tree in your neighbourhood park. Given time, ivy will climb up to the highest branches and completely cover the tree. It’s not a true parasite—it digs in for support only—but unchecked it becomes like an elephant up there and inevitably the tree will buckle under the weight.

As with all highly successful species, ivy propagates in several efficient ways. Any small piece of root left in the soil or thrown on the compost pile will quickly grow into another plant. Seeds remain very viable even after passing through a bird, so they are easily scattered far beyond the boundary of the home garden. And regardless of where they’re dropped, they will quickly establish themselves into a thick sinewy groundcover and then gambol off to the nearest trees. According to the CRD’s invasive species website, ivy on the rampage will inevitably reduce a forest to a clearing, thereby setting up an ideal ecology for an even more notorious invader, Scotch broom.

It’s worth taking precautions to keep bullying species out of the garden and out of the larger landscape as well. No longer do I buy unfamiliar plants without first carefully researching them. I’ve learned that clumping roots stay contained while spreading roots—well, spread, and often in all directions. I watch for wording on plant tags that might suggest aggressive growth, and keep in mind that nursery associates are not really in a position to tell me to pass on that plant in my shopping cart. And though it might seem a tad ungrateful, I’m wary of unfamiliar offerings from friends and neighbours. I’m equally careful when I give plants away.

A little vigilance up front can protect community parks and green spaces from ruin by invasion. It will also prevent hours and hours of tedious or backbreaking work in the home garden. For me with my aching hands and freshly blunted garden tools, that’s a mighty powerful motivator.

Trudy Duivenvoorden Mitic was pleasantly surprised that she grew a few muscles while conceptualizing and creating this column. Writing about gardening combines two of her long-held passions.