Can handle light frost
Sow seeds in a finely textured garden bed in full sun as soon as soil can be worked. In mild winter areas, where the ground doesn’t freeze, plant in fall for next spring’s bloom. Space seeds 1 to 2 inches apart and cover 1/2 inch deep. Keep seed bed moist until seedlings emerge in 7 to 10 days. Weed and water carefully. Thin seedlings to 6 to 8 inches apart.
Sow seeds 1 to 2 inches apart in a container of seed starting mix, 2 or 3 weeks before last expected frost. Cover 1/2 inch deep, keep moist and provide a good light source until seedlings are transplanted outside. Plant 6 to 8 inches apart into fertile garden soil in full sun when plants are 3 to 4 inches tall. Seedlings grow quickly; plant out before the roots get crowded.
In Mild Winter Areas the best cornflowers (aka Bachelor Buttons) result from seeds sown in fall to bloom the next spring. In Cold Winter Areas where ground freezes, plant in early spring to get sturdy plants that will flower for many weeks if faded blossoms are removed.