Centaurea macrocephala (Giant Knapweed)
Centaurea macrocephala (Giant Knapweed) is a large, clump-forming perennial boasting large, bright yellow, thistle-like flowers, 3-4 in. wide (7-10 cm), enclosed in shiny, papery brown bracts in early to mid-summer, Blooming for 2-3 weeks, the blossoms attract bees, butterflies and other pollinating insects.
Centaurea macrocephala (Giant Knapweed) is a large, clump-forming perennial boasting large, bright yellow, thistle-like flowers, 3-4 in. wide (7-10 cm), enclosed in shiny, papery brown bracts in early to mid-summer, Blooming for 2-3 weeks, the blossoms attract bees, butterflies and other pollinating insects. The bold blossoms appear atop sturdy, stiff stems above the foliage of broadly lance-shaped leaves. Native to the Caucasus, Giant Knapweed self-seeds readily and can become invasive. It can out-compete grasses and other forage species, reducing food sources for wildlife and livestock. It is very difficult to remove once established.
- Grows up to 3-4 ft. tall (90-120 cm) and 1-2 ft. wide (30-60 cm).
- Performs best in full sun in dry to medium, well-drained soils.
- Good choice for beds and borders, coastal gardens, cottage gardens, prairies, and meadows. Excellent fresh-cut flowers. Good for dried arrangements.
- No serious pest or disease issues. Keep an eye out for powdery mildew.
- Deadhead regularly to prolong flowering.
- Propagate by seed sown in pots in a cold frame in spring or propagate by division in spring or autumn.
- Centaurea macrocephala is native to the Caucasus, where it grows in mountain meadows.
- Find where this species is invasive in the United States.
Requirements
Hardiness | 3 – 7 |
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Heat Zones | 1 – 7 |
Climate Zones | 2, 2A, 2B, 3, 3A, 3B, 4, 5, 6, 7, 8, 9, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 |
Plant Type | Perennials |
Plant Family | Centaurea – Cornflowers |
Exposure | Full Sun |
Season of Interest | Summer (Early,Mid) |
Height | 3' – 4' (90cm – 120cm) |
Spread | 1' – 2' (30cm – 60cm) |
Spacing | 16″ – 24″ (40cm – 60cm) |
Water Needs | Low, Average |
Maintenance | Low |
Soil Type | Chalk, Clay, Loam, Sand |
Soil pH | Acid, Alkaline, Neutral |
Soil Drainage | Moist but Well-Drained, Well-Drained |
Characteristics | Dried Arrangements, Cut Flowers, Showy |
Tolerance | Drought, Dry Soil |
Attracts | Bees, Birds, Butterflies |
Garden Uses | Beds and Borders |
Garden Styles | Coastal Garden, Informal and Cottage, Prairie and Meadow |