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Evil Plant Invaders: The Knapweed Wave of Deathknapweed0001

Walk any trail in the woods of the american west and you’re likely to see spotted knapweed. Locals have come to know knapweed as an invasive plant. It shows up where it’s not wanted, it out competes native plants, and it spreads quickly, seemingly taking over every field and hillside with little chance to stop it.  While many see knapweed as a tough, adaptable invader, few realize how evil and menacing this plant truly is.


Common thinking about spotted knapweed (and other invasive species) has often been that they thrive here because our hills and fields have none of the insects, pests, and other diseases that act as natural enemies in their native lands. Here in our hills and fields, free from the natural enemies that keep them in check, these non-native species run wild. But that’s only part of the story. Knapweed, it turns out, is downright mean, and it has no regrets about killing its neighbors.

Knapweed secretes a chemical called catechin. Catechin triggers stress messengers in neighboring plants, which turn on the genetic production of oxidants, free radicals. These free radicals travel upward from the plant’s roots in what scientists call a cellular “wave of death”. Neighboring plants, in effect, kill themselves. Scientists have found that this death cycle is triggered within 60 minutes of exposure to catechin. In short, catechin causes nearby plants to commit suicide.

So, next time you find spotted knapweed along your favorite trail, in your fields, or on your front lawn, beware. This is not just a tough, tenacious plant out competing our locals for nutrients and water. It’s a creature so mean that its neighbors commit suicide, a stone cold killer carrying out a campaign of chemical warfare.


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