Archive for July, 2010

Jul 01 2010

Pink Invader

Published by under Plants

One of the prettiest flowers you’ll see by the road at this time of year is one of the most aggressive, invasive plants in North America. 

Crown vetch (Coronilla varia L.) was introduced in the U.S. in the 1950’s during our interstate highway boom.  It was hailed at the time as a fast growing, drought resistant ground cover and planted extensively along the new highways to eliminate the need to mow.

Those same characteristics allowed it to smother the native plants it encountered in its path. 

Crown vetch is native to Europe, southwest Asia and northern Africa.  It thrives in open, sunny places, spreading by seed and rhizomes.  It has no North American enemies, nor can it be eaten by farm animals or wildlife because it contains nitroglycosides which cause slow growth and paralysis if consumed in large amounts. 

Sixty years after its introduction to America, crown vetch is listed as invasive in 45 states.  If you’ve ever tried to eradicate it you’ll know why.

I once received a seed packet of mixed wildflowers as a thank you gift for donating to an environmental group.  I sowed the seed in my front garden and expected a beautiful mix of native wildflowers.  To my dismay the seed company included two crown vetch seeds in the mix.  I foolishly let those two plants grow the first year.  (I am not much of a gardener.)

The next spring the annuals did not re-seed and I was left with two perennials and two overwintering crown vetch plants.  I weeded out the vetch and planted new flowers but the vetch root system had spread so it reappeared in more places than I had pulled up.  I weeded again.  It grew again.  The crown vetch was overtaking the entire plot.

The only solution was to give up on my new flowers and aggressively pull out every crown vetch plant and its root as soon as it appeared.  It took two years of meticulous weeding before I eradicated it from my small garden plot.

Sadly, the seed companies still sell crown vetch.  

You can buy this pink invader, but DON’T! 

(photo by Trisha M. Shears via Wikimedia Commons.  Click on the photo to see the original.)

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