Direct sow eschscholzia seed outdoors where they are to grow from March to May or in September for overwintering. Autumn sowings will flower in late spring. Choose a position in full sun on any poor, well drained soil which has been raked to a fine tilth. Sow seeds thinly, at a depth of 1cm (1/2") in drills spaced 15cm (6") apart and cover seed with its own depth of soil to exclude light. Water the ground regularly, especially during dry periods. Germination usually takes 14-21 days. When seedlings are large enough to handle, thin them out to 15cm (6") apart.
Alternatively, sow California poppies indoors from February to March at a temperature of 15-21C (60-70F). When seedlings are large enough to handle, transplant and grow them on in cooler conditions until large enough to plant outdoors.