Annual
Bachelor's Button (Cornflower)
Centaurea cyanus · Asteraceae
Also called: Cornflower, Bluebottle, Boutonniere Flower
Bachelor's Button (Cornflower) (Centaurea cyanus) is a low-water annual well suited to Tucson and the low desert. It grows to 12-30 in tall and 6-12 in wide in full sun.
Bachelor's Button (Cornflower) at a glance
- Water use
- Low (established)
- Sun
- Full sun (6+ hours) for the most flowers and strongest stems.
- Mature size
- 12-30 in tall and 6-12 in wide
- Growth rate
- Fast (quick from seed within the cool season)
- Bloom
- Classic blue, plus pink, white, lavender, and maroon, Late winter through spring in Tucson (Mar-May).
- Cold hardiness
- Cold-hardy; established seedlings tolerate Tucson winter frosts and light freezes. Heat-intolerant and declines by early summer.
- Soil
- Well-drained soil; tolerant of poor, lean, and alkaline desert soils. Heavy, rich soil produces floppy growth.
- Native range
- Europe (Mediterranean/temperate Europe). Grown as a cool-season annual in Tucson.
- Best used as
- Cool-season wildflower beds and meadows, Cut flowers, Pollinator gardens, Borders and naturalized drifts
- Wildlife
- Excellent for pollinators; attracts bees and butterflies, and seeds feed birds. Extrafloral nectaries also draw beneficial insects.
- Toxicity
- Non-toxic to people and pets; the flower petals are edible and sometimes used as a garnish.
How to grow Bachelor's Button (Cornflower) in Tucson & the low desert
Watering
A cool-season annual: direct-sow seed in fall (Oct-Nov) or late winter. Water to establish, then water moderately and allow the soil to dry between irrigations; this is one of the more drought-tolerant cool-season annuals and dislikes wet feet. Finishes as heat arrives in late spring.
Fertilizer & nutrients
Low feeder. A little compost at planting is usually enough; over-fertilizing (especially nitrogen) yields lush leaves and fewer blooms.
Pruning & care
Deadhead regularly to extend bloom and prevent prolific self-seeding; pinch young plants once to encourage branching. Excellent long-lasting cut flower.
Notes
A tough, low-water cool-season annual well suited to fall direct-sowing in Tucson for spring bloom. It self-seeds readily and pairs well with other cool-season wildflowers like larkspur and poppies; deadhead if you want to control reseeding. Replace/re-sow each season as it cannot survive low-desert summer.
Sources: University of Arizona Cooperative Extension / Pima County Master Gardeners; Brad Lancaster Sonoran Desert Planting Calendar; Tucson Organic Gardeners Planting Guide