Cornflower
Also known as
Bachelor's button, Blue cornflower, Bluebottle
Keep this plant’s care guide close at hand.
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Centaurea cyanus, commonly called cornflower or bachelor's button, is a cool-season annual in the Asteraceae. Plants form upright, branching clumps 12–36 in tall, with narrow, gray-green, slightly hairy leaves. Showy flower heads, most famously vivid ‘cornflower blue,’ appear singly on wiry stems from late spring through summer, attracting bees, butterflies, and beneficial predators. Modern cultivars expand the palette to white, pink, maroon, and bicolors, with both single and double forms. Originally a cereal-field weed of Europe, it thrives in poor, well-drained soils and is valued for meadow-style plantings, borders, and cutting gardens. The long, straight stems and papery florets make excellent fresh and dried cut flowers. Easy from direct sowing, it naturalizes lightly where soil is occasionally disturbed and summers are not overly hot. Deadheading extends bloom. Plants reach 30–90 cm, depending on fertility and climate, and often self-support but may benefit from neighboring companions. Historically emblematic in European folklore and ornamental horticulture, it is also used as an edible garnish and herbal tea coloring.
Taxonomy
Properties & Requirements
How to care for Cornflower
Water
Water to establish, then keep evenly moist but never waterlogged. After seedlings are 3–4 inches tall, allow the top inch of soil to dry between waterings; aim for roughly 1 inch (25 mm) of water per week from rain and irrigation combined. In heat or containers, check more often and water deeply at the base to keep foliage dry. Mulch lightly to moderate evaporation, but avoid thick, soggy mulches in cool, wet climates.
Light
Provide full sun for best stem strength and flower production—at least 6–8 hours of direct light daily. In cool maritime or continental climates, all-day sun is ideal. Where summers are hot, light afternoon shade can reduce stress and prolong bloom without dramatically reducing flower count. Too much shade leads to lanky, floppy plants and fewer, paler flowers. Indoors, grow under bright LEDs delivering 12–14 hours daily if starting transplants.
Nutrients
Lean soils produce the strongest, most floriferous plants; excessive nitrogen encourages lush foliage and flopping. At planting, incorporate a thin layer of finished compost or a low-rate, slow-release, balanced fertilizer skewed toward phosphorus and potassium (e.g., 5-10-10). In containers, feed monthly at 1/4–1/2 strength with a bloom-formula liquid. Side-dress once midseason only if growth stalls. Avoid high-salt fertilizers and manure-heavy amendments that retain too much moisture.
Temperature
A hardy annual, cornflower prefers cool conditions and tolerates light frosts. Optimal growth and flowering occur around 55–75°F (13–24°C). Seeds germinate best at 60–68°F (16–20°C). In hot-summer climates, expect reduced bloom and shorter season above 85°F (29°C); provide afternoon shade and extra water, or grow as a fall–winter annual. Seedlings survive brief dips to about 25–28°F (-4 to -2°C) with protection, but sustained freezes below that can damage buds.
