I just divided a large clump. Below is some info I copied off the web about it. I will be bringing some to the fall Green Elephant swap, but have plenty for other trades as well. The divisions don't seem to have a lot of root, but the plant was healthy so I'm going to assume that's ok.

Cathy

The Centaurea ÂBachelor's ButtonÂ, Centaurea montana, also know as Cornflower and Blue Bottle, has small thistle-like single flowers at the end of a delicate stem, being bright blue and very showy, with gray-green foliage. With a height of 24" and a plant width of 12-24", it is an excellent late summer to early fall bloomer. If cut back after blooming, it will continue to produce new blooms throughout the season. Centaurea ÂBachelor's Button is tolerant of cool winters.

Place it in poor, dry, to moderately moist, well-drained soil in full sun will help it to bloom throughout early to mid-summer. The gray-green, lance-shaped foliage add contrast to this plant. This plant knows no serious insect or disease problems. Use Centaurea ÂBachelor's Button massed in border fronts, cottage gardens or naturalized areas. For planting with other perennials, try ÂIllumination Vinca, ÂVariegated Sedum or Echinacea ÂPurple ConeflowerÂ.