As a comment about Sea Holly (Eryngium 'Sapphire Blue')
This plant is stunning. I have it in full sun all day in average garden soil and it is still vibrant. It starts out fairly silvery but deepens to a dark rich blue. The blooms last almost all summer. I have tried to save seeds this summer and will find out next spring if I have been successful. I lost one of the three I planted the first year (2008), moved the remaining two at least three times, and finally this summer (2011) both plants bloomed prolifically.