Sunday, June 22, 2008

Don't let Scotch broom's pretty flowers fool you
June 20, 2008

I drove up-Island to Courtenay one night last week and was treated to a spectacular sight. The normally drab stretch of the Inland Highway north of Parksville had been transformed into a twinkling sea of blue lupines and yellow broom, which dazzled me all the way to my destination.
Unfortunately, I knew too much about broom to be able to give in fully to the pleasure of the moment. It was a beautiful sight to behold, but hard to ignore what it meant to be passing through dense thickets of broom on both sides of the road for well over an hour.
Scotch broom is native to Africa and the Mediterranean, but made its way here after Capt. Walter Grant brought a handful of seeds to the Island in 1850 from his travels in Hawaii. Three plants grew from the seeds he planted in Sooke. Within 50 years, the plant had naturalized on the Island.
In simpler times, B.C.’s Highways Ministry used to plant Scotch broom along our highways for its cheery colour. That stopped after everyone figured out that the tenacious plant takes over in every sunny spot where it gains a foothold, squeezing out native species and producing an alarming 18,000 seeds per plant each year.
We also came to see over the years that broom was tough to poison, difficult to plough under, resistant to seemingly all insect predation, and too woody and unpleasant for any animal to consider eating. It wreaked havoc with reforestation. It drove up the cost of road and power-line maintenance.
Still, we let it get away from us just the same. Here on the Island, Scotch broom now covers more than 300,000 hectares - 10 per cent of the total land mass.
Oh, it’s a pretty plant, all right. But it’s bad news on just about every other front.
Scotch broom has yet to make the province’s official “bad weed” list, but it’s the source of much concern. It’s a particular problem on southeastern Vancouver Island due to its disruptive impact on two tree species that thrive in our region and few other places: Garry oak and Douglas fir.
Broom certainly isn’t the only problem facing those trees in these wild days of Island development. But its aggressive, take-no-prisoners style of growth blocks sun to new seedlings. Broom also wipes out plants that Island deer depend on for food, and creates such dense thickets in open, sunny spaces that resident quail are forced out of their habitat.
The time to do something about broom is right now, when the bloom is on. Waiting any longer allows the seeds to develop, and ultimately to be spread even farther afield through our fruitless attempts to burn, bury or otherwise destroy the resilient seed pods.
But whose job is it to curb the spread of bad plants? That there’s no real answer to that question perhaps explains why Scotch broom has flourished in B.C.
The Invasive Plant Council of B.C. identified the problem nicely in the title of a symposium on the issue a few years back: “Weeds Know No Boundaries.” Controlling the spread of invasive plants requires, at a minimum, the co-operation and commitment of all surrounding landowners. With B.C.’s mishmash of Crown land, aboriginal reserve, federal land, forest reserve and private property, it’s a major challenge just to accomplish that initial step.
Small wonder, then, that topping the plant council’s list of 10 biggest challenges around tackling invasive species is the task of “improving co-operation” between B.C. landowners. It has to be all for one and one for all when you’re talking about plant control, because nobody’s going to put in the hard work of wiping out broom on their property only to have a few hundred thousand seeds drift down from neighbouring lands where the owner didn’t bother.
Loss of habitat is the major reason for the extinction of native flora and fauna in B.C. But the spread of invasive species comes a close second. On the heavily developed southern Island, that’s a one-two punch for native species.
A 1997 inventory of B.C.’s sensitive ecosystems found only eight per cent of our Coastal Douglas fir region remained in a “relatively natural state.” By 2002, a further 8,800 hectares had been negatively affected. The losses are heaviest in second-growth forest, and you can bet that Scotch broom is doing its part to make matters worse.
Want to join the battle against broom? Visit for tips on how to take action.
As for those lovely lupines, enjoy. They’re native.

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