Seeds of Celosia argentea L. from two cultivar groups Amigo F₁ and Gloria F₁ were sown every week from 1 to 22 March 2006 into containers in a warm glasshouse. After 2 weeks the seedlings were potted into 9-cm pots and placed in a long-day glasshouse. After 3, 4, 5 and 6 weeks of vegetative growth all plants were transferred from a long-day glasshouse to a short-day glasshouse. Celosias cultured at different long-day periods flowered at the same time regardless of the sowing date. Plants of the best quality were obtained after 5 weeks of long days in the Amigo F₁ group and after 3 weeks in the Gloria F₁ group.