Cornflowers, also known as Bachelor’s Buttons (Centaurea cyanus), are easy-to-grow annual wildflowers prized for their ruffled, thistle-like blooms. For plants sown in the spring, the initial flowering period typically begins in late spring. This bloom continues steadily through the middle of summer.
The Primary Blooming Season
The primary flowering period for cornflowers grown from spring-sown seed begins in late May or early June. This initial bloom is triggered once the annual plant has reached maturity following the last spring frost.
This concentrated flowering cycle usually lasts between four to six weeks, depending on the cultivar and local weather conditions. Since the cornflower is an annual, its goal is to set seed to ensure the next generation. Once the initial flush of blooms fades, the plant naturally shifts its focus toward seed development, causing flowering to slow down significantly around mid-July.
Encouraging a Second Flush of Blooms
Gardeners can extend the cornflower’s flowering season into late summer and early autumn through deadheading. This maintenance practice involves removing the spent flower heads, which prevents the plant from expending energy on forming viable seeds.
Preventing seed set tricks the plant into diverting resources back into producing new buds and blooms. To properly deadhead, trim the stem back to a lower leaf node or a secondary side shoot, which encourages branching. While the second flush of flowers is typically less abundant than the initial spring display, this action can add several weeks of color.
Environmental Factors Influencing Timing
The start date of the cornflower bloom is influenced by several environmental variables. Plants grown from seeds sown directly into the soil in early spring will bloom later than those started indoors and transplanted. Autumn-sown cornflowers establish a root system over winter, allowing them to flower weeks earlier in the spring.
Sunlight exposure is a major determinant, as Centaurea cyanus requires at least six hours of direct sun daily. Planting in a partially shaded location will delay maturation and the onset of flowering. Temperature also plays a role, with blooms appearing sooner in warmer climates compared to cooler zones. Applying a fertilizer high in nitrogen promotes leafy growth at the expense of flower production, potentially delaying the bloom.