Plant perennial cornflower and stand back. No, it’s not that bad! It grows in almost any soil, but it flops over if allowed to dry out too much. It is more aggressive in rich soils, so avoid fertilizing. Deadhead as soon as flowers are spent to keep it blossoming and reduce the number of self-sown seedlings. Like all spreaders, it is easily increased by dividing the clumps or by transplanting the seedlings. Perennial cornflower does best in cool regions and does not like hot, humid climates.
Also called mountain bluet, perennial cornflower is a European member of the vast daisy family. Its brilliant deep blue blossoms, 2 to 3 inches across, are touched with red at the center. The uniquely shaped petals are frilled and fringed in a delicate arrangement on a thistlelike flower head. Perennial cornflower provides an ample supply of cut flowers that enrich any flower arrangement. (Annual cornflower is also called bachelor’s button and is one of the most useful flowers in the cutting garden.)
Perennial cornflower thrives in full sun but is almost as happy in part shade, where it has a tendency to be floppier. Since this plant can be a spreader (especially in northern gardens), locate it with care. Avoid placing perennial cornflower in a border with delicate plants that are easily overcome by aggressive colonizers. Take advantage of cornflower’s habit by using it to hold a sunny bank, but be careful not to let the soil dry out before the cornflower is well established. It provides a colorful companion for all but the shortest of shrubs.
ZONES: 3–8
BLOOM TIME: Summer
LIGHT: Full to part sun
HEIGHT: 18–24 inches
INTEREST: Masses of frilly brilliant blue flowers over a long season