Mary Stella, I am not sure if they simply could not overwinter in the bed or declining over long time? Another issue is water + temperature in summer. Irises and lilies could be more drought-resistant than peonies - I am watering my Bartzella and Cora Louise this year because of last year disappointment with flowers - will let you know if it makes any difference. They are planted at driveway near stone curb - raised one. I was wondering as well whether roots were too close to stones and too cold in winter or it was not enough of water - drainage was excessive.
