No 5 star of the second magnitude in my plant world is campanula lactiflora. Out now and lasting just a few weeks is this lovely silvery blue, four feet tall member of the campanula family. Beautiful in a vase (though with an odd damp smell - we spent ages looking around for the source of the smell, thinking we had left a damp cloth lying).
No attention required other than cutting to the ground in the autumn.
How beautiful and how simple is that? A silver star.