Centaurea Species, Cornflower, Perennial Bachelor Button, Red Knapweed
Centaureaatropurpurea

Synonym:Centaurea oliveriana

Category
Perennials

Water Requirements
Drought-tolerant; suitable for xeriscaping
Average Water Needs; Water regularly; do not overwater

Sun Exposure
Full Sun

Foliage
Herbaceous

Foliage Color
Bronze

Height
12-18 in. (30-45 cm)
18-24 in. (45-60 cm)
24-36 in. (60-90 cm)

Spacing
18-24 in. (45-60 cm)
24-36 in. (60-90 cm)

Hardiness
USDA Zone 7a: to -17.7 °C (0 °F)
USDA Zone 7b: to -14.9 °C (5 °F)
USDA Zone 8a: to -12.2 °C (10 °F)
USDA Zone 8b: to -9.4 °C (15 °F)
USDA Zone 9a: to -6.6 °C (20 °F)
USDA Zone 9b: to -3.8 °C (25 °F)
USDA Zone 10a: to -1.1 °C (30 °F)

Where to Grow
Grow outdoors year-round in hardiness zone

Danger

Bloom Color
Dark Purple/Black
Maroon/Burgundy

Bloom Characteristics
Flowers are good for cutting
Flowers are good for drying and preserving
This plant is attractive to bees, butterflies and/or birds

Bloom Size

Bloom Time
Mid Summer
Late Summer/Early Fall

Other details
May be a noxious weed or invasive

Soil pH requirements
6.1 to 6.5 (mildly acidic)
6.6 to 7.5 (neutral)
7.6 to 7.8 (mildly alkaline)

Patent Information
Non-patented

Propagation Methods
Self-sows freely; deadhead if you do not want volunteer seedlings next season

Seed Collecting
Allow seedheads to dry on plants; remove and collect seeds