Centaurea or knapweed when we think of the garden plants the name knapweed seems in a bit harsh. They are silvery leaved evergreens and when in flower and make for a tidy little clump with attractive thistle-like flowers that are important to many garden friendly insects. They like any soil and full sun but can stand deciduous shade. If you have a waterlogged site then it will not like it. They can be reproduced from seed to move around the garden.