I do have a penchant for blue flowers, and for easy care perennials. If I re-named this perennial, I would call it ‘Easy Blue’. Although Centaurea montana already has many common names: mountain bluet, perennial blue cornflower or perennial bachelor’s buttons. This was one of the first perennials I grew, and had several because I had purchased under a couple of those common names not realizing it was the same plant! The blue sparkle flowers are the best feature, exploding like fireworks from pineapple, egg-shaped buds. The somewhat sprawling grey-green foliage is a gentle, bushy backdrop. They can aggressively self-seed so it’s worth putting attention to deadheading (or not, if you want more!). The first rush of flowers comes late spring – once the leaves start to brown off you can cut back to new growth for a second round of bloom later in the summer.
Technical stuff – Perennial bachelor’s buttons/Centaurea montana, hardy perennial to zone 4, height and spread of about 24”, prefers full sun and poor to average soil, will bloom in part sun but can get leggy, drought resistant, there are several Centaurea species including the annual Centaurea cyanus.