The large white, scented flowers of this attractive woody perennial are really eye-catching and sit beautifully with the glaucous leaves.  The petals look like crinkled silk and the large central boss is yellow. It is said to be vigorous and spreads by suckers but we have longed for the one in our garden to do just that!  After 4 years it has sent up two suckers only.  Grows to about 6' tall and likes fertile, well-drained soil and full sun.  Hardy in most of UK but shelter from cold winds.