Mongabay has a story about an invasive, purple-flowered plant in Iceland that they call a "purple menace"...but it's not purple loosestrife. Turns out Alaskan lupines (Lupinus nootkatensis), introduced for land reclamation and also for ornament, have escaped from cultivation and naturalized into the Icelandic landscape. Unfortunately, they are fairly aggressive invaders, often interrupting the normal recovery of a site and preventing native plants from establishing. Since lupines are nitrogen-fixers, their growth alter soil nutrient levels, further tipping the balance away from native species that evolved without that extra nitrogen boost. Alaskan lupine is just one of 10,000 different plant species that are known to have been introduced to Iceland.