Knapweed (Dusty-Miller)
Centaurea species. ASTERACEAE (COMPOSITAE).
Planting and Growing Knapweed
You’ll find everything you need to know to plant and grow knapweed in the accompanying table’s tabs:
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- Flowers, foliage, and root structure of knapweed
- Plant hardiness and growing conditions for knapweed
- Season of bloom and planting time for knapweed
- When, how deep, and where to plant knapweed
- How to plant knapweed
- Watering, fertilizing, care, and pests or diseases of knapweed
- Landscape and container uses of knapweed
- Comments about knapweed and its features
Growing Knapweed
Nearly 500 species of bushy, rounded, deciduous annual, biennial, and perennial herbs, 1–5 ft. (30–150 cm) tall. Fuzzy, gray green, often silver, needlelike, often deeply cut leaves, to 1 ft. (30 cm) long, with gray, white undersides.
Commonly cultivated species include basket flower, Centaurea americana; perennial cornflower or mountain bluet, Centaurea montana; velvet centaurea or silver dust, Centaurea cineraria; and Caprian cornflower, Centaurea gymnocarpa. Sweet-sultan, Centaurea moschata, is a related annual species.
See also Cornflower, Centaurea cyanus, an annual flowering plant.
Planting and Care Guide
Blooms
Many blue, lavender, pink, yellow, fringed, tubular, thistlelike, tufted flowers, 2–3 in. (50–75 mm) wide, either single or clustered, in spring–summer. Silver-leaved species are grown primarily for foliage.
Best Climates
Hardy. Zones 3–9.
Soil Type and Fertility
Moist, well-drained loam. Fertility: Average. 6.5–8.0 pH.
Where and How to Plant
Early spring, after frost hazard has passed, zones 3–7; autumn, zones 8–9, in full to filtered sun, 1–2 ft. (30–60 cm) apart.
Proper Care
Easy. Keep moist; allow soil surface to dry between waterings. Fertilize annually in spring. Stake taller species. Propagate by division, seed.
About This Plant
Good choice for accents, backgrounds, beds, borders in arid, formal, rock gardens. Good for cutting. Disease resistant. Aphid susceptible.