Centaurea is Mountain Bluet or Perennial Bachelor's Button
|Centaurea Amythest Dream|
There are hundreds (between 350 and 600) species in the plant's family, Asteraceae. Other plants in the genus include starthistle, knapweed and cornflowers.
Bluestone Perennials has Amethyst Dream though their photo looks more blue than mine.
Perennial Bachelor's Buttons are hardy in zones 3 to 9 and tolerate dry locations as long as they get the half day shade they need in our area.
Forest Farm says they are cold hardy to zone 5 and that butterflies love them.
Missouri Botanical Garden says they are cold hardy to zone 3 in full sun. "Avoid rich, fertile soils."
No diseases or insect problems in our garden, though Fine Gardening says: White mold, rust, downy and powdery mildew, thread blight, and Southern blight can occur.
Doug Green calls Mountain Bluet a foolproof plant and suggests that it is easy to grow from seed. Check it out at http://www.doug-greens-
Urban Gardener has seeds!
I wonder why it isn't in more gardens. Consider adding it to yours.