Plant for heavy clay soil
 

The garden at the back of our bungalow is heavy clay soil with a four
inch raised up lawn. The previous occupant must have spent a fortune
to cover the clay with the four inch thick layer of some fibrous stuff
supporting the lawn and the soil it is growing in. Unfortunately the
surrounding edge is still just clay. Geraniums and rose bushes are
doing well but not much else. My wife and I are both disabled so what
we want is a plant to fill the border that looks after itself!

Any ideas?

Steve