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Centaurea scabiosa (Greater Knapweed)

Greater Knapweed, Black Top, Scabious Knapweed, Greater Centaury, Centaurea scabiosa var. petrophila

Centaurea scabiosa, Greater Knapweed, Black Top, Centaurea scabiosa var. petrophila, Purple Cornflowers

Thriving on neglect, Centaurea scabiosa (Greater Knapweed) is an upright perennial with large purple, thistle-like flower heads, 2 in. wide (5 cm), adorned with prominent outer florets from mid-summer to early fall. Attracting bees, butterflies, and other admirers, the bold blossoms appear atop sturdy stems above the foliage of pinnately lobed leaves. Native to Europe, Greater Knapweed self-seeds readily and can become invasive.

  • Grows up to 30 in. tall (75 cm) and 12-16 in. wide (30-40 cm).
  • Performs best in full sun in dry to mesic, well-drained soils. Tolerant to poor, alkaline soils.
  • Good choice for wildlife gardens, prairies, and meadows.
  • No serious pest or disease issues. Keep an eye out for powdery mildew. Deer resistant.
  • Propagate by seed.
  • Centaurea scabiosa is native to Europe, where it grows in dry grasslands, hedgerows, and cliffs on lime-rich soil.
  • Find where this species is invasive in the United States.

Requirements

Hardiness 4 - 8
Plant Type Perennials
Plant Family Compositae
Genus Centaurea
Common names Black Top, Knapweed
Exposure Full Sun
Season of Interest Summer (Mid, Late), Fall
Height 2' - 3' (60cm - 90cm)
Spread 1' - 2' (30cm - 60cm)
Spacing 16" - 18" (40cm - 50cm)
Maintenance Low
Water Needs Average
Soil Type Chalk, Clay, Loam, Sand
Soil pH Acid, Alkaline, Neutral
Soil Drainage Moist but Well-Drained
Characteristics Showy
Native Plants United Kingdom
Tolerance Drought, Deer
Attracts Bees, Birds, Butterflies
Garden Styles Prairie and Meadow
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Alternative Plants to Consider

Centaurea cyanus ‘Jubilee Gem’ (Cornflower)
Centaurea dealbata (Persian Cornflower)
Centaurea dealbata ‘John Coutts’ (Persian Cornflower)
Centaurea cyanus ‘Black Gem’ (Cornflower)
Centaurea cyanus ‘Pinkie’ (Cornflower)
Centaurea cyanus ‘Snowman’ (Cornflower)

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Companion Planting With Annuals
Native Plant Alternatives to Centaurea cyanus (Cornflower)
While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates. The description of these plants has been written based on numerous outside resources.
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Requirements

Hardiness 4 - 8
Plant Type Perennials
Plant Family Compositae
Genus Centaurea
Common names Black Top, Knapweed
Exposure Full Sun
Season of Interest Summer (Mid, Late), Fall
Height 2' - 3' (60cm - 90cm)
Spread 1' - 2' (30cm - 60cm)
Spacing 16" - 18" (40cm - 50cm)
Maintenance Low
Water Needs Average
Soil Type Chalk, Clay, Loam, Sand
Soil pH Acid, Alkaline, Neutral
Soil Drainage Moist but Well-Drained
Characteristics Showy
Native Plants United Kingdom
Tolerance Drought, Deer
Attracts Bees, Birds, Butterflies
Garden Styles Prairie and Meadow
How Many Plants
Do I Need?
Explore Great Plant Combination Ideas
Centaurea
Guides with
Centaurea
Not sure which Centaurea to pick?
Compare Now

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