I probably ought to make this a series - heaven only knows that I've made plenty of mistakes over my time gardening. Others might as well learn from my hard-headedness!
So, moving on to this particular example.... Last year I was cleaning out an area where a large Austrian pine had succumbed to pine wilt. We had had the pine removed earlier last spring, leaving a large area that was bare of almost all vegetation and coated with pine needles. This area was right next to the northeast corner of the house, so it seemed like a logical expansion for the front flower bed.
Of course, as is typical under a large evergreen, there were a few seedlings that had grown up from seeds dropped by birds, thoughtfully provided with a little bolus of fertilizer to help them establish. We didn't want any large trees growing that close to the house, so removing the tree seedlings seemed straightforward. However, as I started clearing out the stray clumps of grass and other plants that had managed to claim a spot, I found a small start of a beautiful, almost ferny, low growing plant that seemed to be acting as a groundcover.
I hadn't identified the plant yet, but it had come in naturally and it was quite pretty - providing a ferny effect - but obviously very hardy and definitely providing good cover. Neither of us were too concerned about leaving it for a while. Eventually our mystery plant started blooming, and the blooms were attractive too.
Kansas Wildflower and Grasses page didn't raise any red flags for me. The blooms only made it more attractive. The plant seemed to be staying closely confined, so I let it be. After all, the prairie environment is harsh enough that many "overly aggressive" plants elsewhere behave more reasonably for us.
Boy, was letting it alone a mistake. By last fall, I'd decided that I really didn't want such a rapidly spreading groundcover in that spot, so I tried to dig it out. Shortly after I thought I'd got it all out, I found new sprouts coming up all over the place. By now, the plant was definitely spreading out widely and it was beginning to impinge on several small wildflowers I'd planted during the summer. I dug out it all out again just before frost...and kept my fingers crossed over the winter.
I guess that finger-crossing isn't a particularly effective eradication technique. Wishing and hoping evidently don't work either.
I spent today doing my spring-time clean-up on that bed. The crown vetch has now spread to an area about 6-8' in diameter. Greg and I have decided it's time to pull out the Roundup, much as I dislike resorting to that option. I trust that, by carefully using it, we'll be able to eradicate this infestation, but I sure wish I'd gotten rid of the crown vetch when I first realized it was developing as a "groundcover". Live and learn.
My "live and let live" attitude towards unknown plants has served me well many times, but sometimes it reaches up and bites me. This was one of those times. I'd suggest getting rid of crown vetch immediately, if you ever find even a sprig of it in your garden. A classic example of "Do as I say, not as I did!"