One of the most graceful perennial plants dierama produces clumps of tall grass45like semi45evergreen foliage topped with a profusion of arching flower stems in july and august the exquisite purple bell45shaped flowers of dierama 39blackbird39 drip from incredibly delicate stems swaying and nodding in the slightest breeze as autumn arrives the seed heads make an attractive architectural feature in the border wonderful for cottage gardens gravel gardens and herbaceous border