Above is a picture of turf that is mowed only two or three times a year. As you can see yarrow has established itself nicely in a portion of this field and represents a simple form of what I am talking about, but it is a bit rough for a garden.
Above is a picture I copied from William Robinson's 1881 edition of The Wild Garden in which he suggested planting peonies in the midst of a stand of grass. I experimented with that idea myself as can be seen below.
Below is the same planting with another pleasant surprise. After having killed Incarvillea delavayi a couple of times this Festuca ovina planting proved to be a place for it to thrive. I will continue to search for suitable companions to join this little community.