The last day to register for our annual GRN workshop is Friday, June 14, 2013. We are planning for an interactive set of discussions and tours of prairie restorations. Join us!

When is a weed invasive?

In my last post on king devil I said “most” managers feel this weed is invasive, including myself. Stephen Packard responds back that “This alien hawkweed is not a problem” at his sites. You can read his full comment by clicking on this page by his name. Steve could be right.

If you polled a passel of natural areas managers you would likely find agreement on the following being invasive: sweet clover, leafy spurge, reed canary grass, phragmites, teasel, purple loosestrife, Lespedeza cuniata, and birdsfoot trefoil.

The following weeds might receive mixed opinions on their invasiveness: wild parsnip, Canada thistle, day lily.

After twenty years of going after king devil and not eradicating it I feel comfortable calling it a medium difficulty invasive. This could be due to our soils supporting it better than other places. I would not rank it nearly as difficult as birdsfoot trefoil. Maybe the king devil is just some punk.