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The knapweeds, cornflowers or hardheads are hardy plants that are good for borders, beds or your wild garden. Most are very easy to grow, are excellent for cutting, and some dry very well.
Some varieties may become invasive if planted in good rich soil, so good soil should be avoided if possible.
Blooming times vary anywhere from late spring up to mid autumn, depending on the variety. Some of the early bloomers will also rebloom quite nicely in the fall. The flower colors range from blue, mauve, crimson, rose-pink, purple, white or yellow.
Most have terminal flower heads that are thistle-like and lack true ray florets. Often the outermost florets are large and petaloid and are usually frilled or fringed. The flower heads are surrounded by papery or prickly bracts, which may also be fringed.
Their alternate leaves can be coarsely toothed, rough and oblong, or lobed and rounded at the tips. Leaves are often silvery or even felted, with hairs on one side or both
Centaurea thrive in a sunny location with ordinary garden soil (sweet) and are quite tolerant of dry conditions, but don't like wet feet over winter. Propagate by divisions in early spring or fall.
CULTURE / CARE
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PLANT IN ORDINARY GARDEN SOIL
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TOLERANT OF DRY CONDITIONS
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WILL NOT TOLERATE WET FEET OVER WINTER
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FULL SUN
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GROWS 1-3½ FEET TALL
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CAN BE INVASIVE IN GOOD SOIL
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VERY LONG BLOOMING
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DIVIDE IN SPRING OR FALL
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DIVIDE EVERY 2-3 YEARS
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HARDY IN ZONES 3 - 9 (US)
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CULTIVARS, SPECIES & VARIETIES
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Centaurea dealbata
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Centaurea dealbata 'John Coutts'
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Centaurea dealbata 'Steenbergii'
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Centaurea pulcherrima
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Centaurea gymnocarpa
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Centaurea argentea
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Centaurea cineraria
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Centaurea ragusina
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Centaurea hypoleuca
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Centaurea macrocephala
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Centaurea glastifolia
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Centaurea montana 'Alba'
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Centaurea montana 'Parham'
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Centaurea montana 'Rubra'
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Centaurea nigra
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Centaurea cynaroides
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Centaurea rhaponticum
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Centaurea ruthenica
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Centaurea pulchra major
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Centaurea rutifolia
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