Weed of the Week: Spotted Knapweed

Weed to avoid

Look around you.

They are here.

They are everywhere.

The came here as stowaways on ships arriving from foreign lands, viciously intending to  reproduce and multiply, until they took over the continent.

A task force of serious scientists have profiled these unwanted guests and have made their information and photos available to the public so that they may be caught and eradicated before they succeed in their evil goals of destruction.

You are now being urged to inform yourselves of this danger, and deal with any invaders near you.

For the next six weeks, here in the Golden Star, you will be provided with a profile of an Invasive Alien Weed, along with a picture for easy identification.

Our first fugitive, Centaurea biebersteinii, more commonly referred to as Spotted Knapweed, is already running rampant in this area.

You are probably already familiar with the purple flower that is now blooming on upright, thistle-like stems that can get up to one  and a half meters in height.

The Invasive Plant Council of BC reports that a single Spotted Knapweed plant produces up to 18,000 seeds that can remain dormant in the soil for years.

For this reason, constant vigilance is required when traveling through an infested area, so seeds aren’t accidentally transported on the undercarriage of your vehicle of even on your clothing.

Once a patch of Spotted Knapweed is established, eradication is quite challenging.

Though manual or mechanical removal is effective control,  it requires follow up and should only be done prior to flowering to prevent the unfortunate side-effect of accidentally spreading the seeds.

Fortunately, two insect species (a weevil and a clearwing fly) have been discovered to be highly effective biological agents against spotted knapweed.

In fact, there have already been releases of these bioagents in Golden this year for particularly nasty infestations.

If you notice knapweed plants without heads, then you are likely looking at the job of a bioagent.

If you see a spotted knapweed plant, report it to www.reportaweed.ca or to www.wildsight.ca/invasivespecies if it’s within the town boundaries.