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Centaurea montana (perennial cornflower, mountain cornflower, bachelor's button, montane knapweed or mountain bluet) is a species of Centaurea endemic to Europe. It is widespread and common in the more southerly mountain ranges of Europe, but is rarer in the north. It escapes from gardens readily, and has thereby become established in the British Isles, Scandinavia and North America.
C. montana may be distinguished from other Centaurea species in the region by its usually entire leaves, and the blue-purple colour of the outermost ray florets. It may be distinguished from the cornflower, C. cyanus, by having a single (rarely up to three) flower heads, and by its being perennial, whereas the cornflower has many flower heads and is annual. The closely related C. triumfettii has more narrowly winged stems, narrower leaves and grows in rockier areas.
Centaurea montana grows in gardens where it grows best in sunny positions. It tolerates some light shade. Since the plant is evergreen it can use the light in winter and early spring when deciduous trees and shrubs have no leaves. It tolerates deciduous shade better than evergreen shade and prepares to flower while deciduous plant are bare. Therefore, it can flower reasonably well in light deciduous shade. If the plant is dug up, a new plant can eventually regenerate from small pieces of root left in the soil. Centaurea montana grows well in soils varying from light sand to heavy clay. The plant also grows well in acid, neutral or very alkaline soils. It tolerates drought but cannot tolerate waterlogged conditions.