Mountain bluet, also known as perennial cornflower, is a perennial related to the annual “bachelor’s buttons” (Centaurea cyanus). Mountain bluet is prized by gardeners for its adaptability, large, bright blue flowers—the largest blue flowers of all the knapweeds—and ability to self-seed. Introduced from southern Europe, it is prone to escaping cultivation in drier areas of the province, especially in higher pH soils.
How does it spread?
Mountain bluet is self-fertile, spreading by seed and vegetatively, by creeping rhizomes (horizontal underground stems). It produces copious seed, which can persist in the soil for years, and new plants can easily sprout from small pieces of the rhizome or roots.
Where would I find it?
Mountain bluet is hardy and drought-tolerant, growing well in most soil types and climates but plants prefer full sun to part shade in dry to moist, but well-drained soil. It grows along roadsides, in meadows, pastures and waste/disturbed places, in both open shrub-steppe, and broad-leaved forests in lowland zones.
What problems does it cause?
Mountain bluet escapes cultivation and colonizes quickly, displacing native vegetation. It starts spring growth ahead of native plants and continues growing into late autumn after other plants have gone dormant. The plant can quickly establish and grow into thick stands changing the densities and population composition of native plant species. It also can alter native plant-pollinator interactions and reduce forage opportunities for wildlife and livestock.