I once read that Campanula or Bellflower was a good plant to grow at the base of a hedge as it would grow in the dry soil. At the time my little privet hedge was quite new and there were large gaps between the plants so I decided to plant just one Campanula to see how well it would grow.
That was about ten years ago and now that one plant has spread along the base of the hedge. Apart from tidying it up after flowering, I don't really look after it at all but despite being neglected, at this time of the year it seems to burst into life covering my golden privet hedge with a mass of pale lavender star shaped flowers.
Just the sort of low maintenance gardening that I like.