How to Grow Perennial Cornflower
Centaurea montana
Perennial Cornflower is a vigorous, clump-forming perennial for full sun and well-drained soil. It flowers from May to July with striking blue spider-like blooms beloved by bees and butterflies. Cut back hard after the first flush to encourage a second flowering in late summer. Divide clumps every 2-3 years to prevent it spreading too aggressively. Drought-tolerant once established and fully hardy.
Yearly Lifecycle
Care Essentials
Light balanced feed in spring as growth begins. Avoid high-nitrogen feeds which promote leafy growth at the expense of flowers.
Watch For
- Powdery mildew in dry conditions
- Aphids on young shoots
- Slugs on emerging growth
Companions
Salvia, Geranium, Achillea, Iris
Pet Safety
Care Requirements
Light
Full sun; tolerates partial shade
Grows best in full sun but tolerates light partial shade. Flowering is reduced and plants become more floppy in shade.
Watering
Water to establish; drought-tolerant once settled
Water regularly during the first growing season. Once established, Centaurea montana is drought-tolerant and rarely needs supplemental watering except during prolonged dry spells.
Fertilizing
Light feed in spring only
Apply a light balanced fertiliser in spring. Avoid high-nitrogen feeds which encourage leafy growth at the expense of flowers.
Pruning
Cut back after flowering; divide every 2-3 years
Cut stems back hard after the first flush to promote a second flowering. Divide congested clumps every 2-3 years in spring or autumn to control spread and maintain vigour.
Spacing
45cm apart; allow for spreading
Plant 45cm apart. The plant spreads by rhizomes and can colonise a wide area over time. Plan to divide regularly.
Growing Tips
Cut back for a second flush
Cut stems back by half after the first flowering in June to encourage a second flush of blooms in late summer or autumn.
Divide to control spread
Lift and divide clumps every 2-3 years in spring or autumn to prevent invasive spread and to keep the plant flowering well.
Great for pollinators
The spidery blue flowers are magnets for bees and butterflies. Plant near vegetable gardens to attract beneficial insects.
Spacing & Planting
| Plant spacing | 45 cm |
| Row spacing | 50 cm |
| Mature height | 55 cm |
| Mature spread | 55 cm |
Spreads vigorously via rhizomes. Divide clumps every 2-3 years to control spread and maintain vigour.
