This was my starting point. The parking strip to the left of the sidewalk is turf grass, but the right side of the sidewalk is Achillea millefolium (Yarrow). I've written earlier about how I overseeded my meadow. The result of too much A. millefolium was a carpet of yarrow, with each plant competing with its neighbors. This wasn't a bad thing. But I felt that I ought to strive for something a little better. Yarrow grew aggressively where I seeded it, but didn't make too much of an incursion past the flexible border that I installed on one side of the meadow.
During the year I used a string trimmer on it a couple times and generally wasn't too unhappy about it except that it was so dense that it didn't allow a good opportunity for other plants to grow. I had put in some topography in the meadow area and yarrow definitely preferred the lower and moister soil. The dryer soil on the tops of the hillocks was nearly bare in summer.
When it's watered, yarrow makes a nice, soft, carpet. This is an area of with poorer soil and I like the stunting effect it has on the yarrow growth. Last summer, however, this area was pretty stressed.
It has a fern-like texture that's quite nice. I think it's nicest when it's set off all by itself or by other plants. I don't water frequently, and yarrow doesn't completely die back. As I discovered when I found the perpetually leaky sprinkler head buried in this picture, it likes boggy soil as well.
I re-dug the yarrow meadow and ended up with what you see below. Not complete oblieration, but a definite minimization. I scattered wildflower seeds (hopefully not too many this time) in what I hope will be drifts later this spring.
The roots of the yarrow were densely packed in a mat up to 2 or 3 inches thick. Maybe thicker. Some of the yarrow I dug out like a piece of sod, and just flipped over in its hole. East coast gardeners always advertise that they do this when starting a garden, but it's never worked for me with turf. We'll see if it works with yarrow. The rest of it I knocked the dirt from and threw away. I hated to see compostable plant material go, but it's an aggressive grower and I didn't have faith that it wouldn't infest whatever compost pile I made from it.