Struggles with cedar: it’s all about context

BC's provincial tree can cause challenges for gardeners

“They’re so messy!” a friend exclaims as I stoop to pick up a long flat arc of leaf. Tiny cones litter the ground. A shallow root runs along the soil like a sinister finger. She leads me under her cedar and scrapes her heel into the earth. “See? Hardpan.”

I hrrummph.

Like many gardeners I have mixed feelings about cedar trees. I want to like them: they’re native, graceful and evergreen. A wonderful shade tree, sublimely tolerant of damp soil, our Western red cedars can take a beating and keep on kicking up new growth.

I inherited one that had been topped by a previous owner, so it now has multiple leaders. It’s over four feet wide at the butt and has housed a tree fort, acted as a highway for raccoons (ugh), and a support for a hammock. Valuable privacy cedars provide, and even after this year’s storms and a pruning (I had the crown reduced by a third), it still dances in the wind, waving its long limbs in the breeze.

So what’s not to like? Those sinister roots, for starters. If you’re planning a raised bed near a cedar, take heed. The adventitious roots infiltrate healthy soil, draining water and nutrients while weaving thick mats. As one gardener once said to me after hearing my veg plot plans: “I have two words for you: pond liner.” Well, I didn’t use it and lost a salad bed 20 feet away from a cedar in three years.

Understanding cedar’s physiology is key to living with B.C.’s official provincial tree (Pacific Dogwood – also a tree – is actually our provincial flower). According to UVic botanist Patrick von Aderkas, the leaves and branches that Western red cedars shed acidify the soil and deliver thujone, a monoterpene that acts as a growth inhibitor to other plants. As von Aderkas says, “terpenes are the biggest class of organic compounds in the world, and plants make a lot of them – it’s their answer to language. In this case, the cedar’s thujone is saying ‘you’re not growing under me!’”

So how did I manage to create a semi-shade garden under my cedar? By raking up the messengers and installing irrigation. By no means is this a low-maintenance corner of my garden, but I still manage a decent display with our native Indian Plum Oemelaria and Deer fern Blechnum spicant, the perennials Dicentra (bleeding heart), Disporum cantoniense (a sensational plant), Hosta spp., Ligularia, Carex grass, Bergenia, and the Japanese forest grass, Hakonechloa.

It was reported a couple of years ago that 20 per cent of the red cedars of Saanich have been lost to development since the 1980s. Add the threat of climate change and our provincial tree is on the decline.

If you have a dry shaded area under a cedar, dig in some natives, coddling them for a while to get them established. Try the native shrubs Oregon grape Mahonia, Salal Gaultheria or the ground cover False Lily of the Valley Maianthemum racemosum. For damp shade try Solomon’s Seal Polygonatum and Tiarellas (these look like Heuchera but with charming scented flowers).

Take the position of my farmer friend from Metchosin who came by recently and counted me as lucky to have a towering cedar anchored in a damp corner of the garden. “Dries the soil nicely,” she said.

Proof indeed that with many plants it’s all about context.

Christin Geall is an avid Oak Bay gardener and a creative non-fiction writing instructor at the University of Victoria.