From Metrosideros: "Angiopteris evecta, an aggressive and large invasive fern."
2nd Place with 220 points:
From mygardens: "Winged euonymus is considered an invasive plant in zone 6b, New York. Indeed it does grow all over our property, but it thrives in any location and the colors vary from light pink to deep red, according to how much sun it receives. It is a wonderful backdrop to my other fall colors."
3rd Place with 148 points:
From mygardens: "The purple loosestrife in the photo is an invasive plant. It is very aggressive and there are many reason why it should not be sold or grown, but we control it on our property because of the beautiful fall color and for the nectar for our honey bees. We are in zone 6b. "
Runner Up with 122 points:
From jmorth: "Thistle (Cirsium) - noxious weed with some positive attributes (butterfly and bee appeal). Zone 5b/6a. European native. Pic from an open woodland border in the fall."
Runner Up with 99 points:
From Audrey: "Hedge bindweed, calystegia (or convolvulus) sepium, may be pretty, but it is also one of the most pernicious weeds in my zone 5 garden!"
Runner Up with 87 points:
From arctangent: "A hillside smothered in gorse. Ulex europaeus is an imported species which did the job for which it was imported all too well (dune stabilization), and has now run amok all along the Oregon coast."
Runner Up with 86 points:
From jmorth: "Goldenrod. Z5b/6a. Butterfly magnet for fall-migrating Monarchs. A woodland edge. Prolific self seeder."