Centaurea is a very large genus with many venerable garden - and some disreputable - species. The name is from the Greek kentauros, a centaur, who was believed to have introduced us to the medicinal quality of plants, though it beats me what centaurs could know about medicinal herbs. I guess botanists agree with me because most of the plants here have been reclassified since I learned their names.
Some species, like Dusty Miller, Centaurea cineraria, once in vogue as a bedding plant, are grown for their ornamental silvery-gray foliage. C. cyanus is the old-time annual cornflower, one of the bluest flowers in the garden, beloved by children and goldfinches. There is a southwestern native biennial C. rothrockii, called basketflower for its intricate seedhead, whose tall form is crowned with astonishing two-tone thistle-like flowers in cream and mauve. I only once succeeded with it, starting from seed obtained, ironically, from a British source. It is one to try, if you like a challenge.
Almost as infrequently seen is the perennial Centaurea macrocephala, native to Armenia, with a slew of "common" names, none of which are common. Its stout stems and coarse leaves hold their own in midborder all season, requiring only cutting to the ground in spring and the dispatching of seedheads if you don't find them interesting. The flower bursts out of its bud like a present being unwrapped from layers of gift-wrap. Small lance-shaped leaves, bright green, and kind of cobwebby, clasp together at the top of the stalk, then unwrap to reveal a globe of overlapping, minutely fringed bracts, satiny and tawny like Enstrom's toffee. Finally the golden yellow thistle erupts from the bracts. Returning from vacation the first time mine bloomed, I mistook the papery brown bracts for seedheads, assuming they had flowered during my absence, and promptly decapitated the buds.
Another yellow thistle-head, C. solstitialis, tellow star-thistle, recently starred as Pitkin County Land Management's weed villain of the week. Its radiating collar of sharp spines reminds me of the crown of thorns Jesus wore in my Sunday School illustrations. William A. Weber in his "Colorado Flora," calls it an "extremely noxious and potentially destructive weed."
My own sunny Centaurea macrocephala is pretty well behaved, a slowly spreading clump that has generated only a few welcome seedlings not far from the parent plant over the years. I wouldn't be without this bold fascinating plant. Then again, Mr. Weber says it too is "a potentially serious pest." When did gardening become so complicated?