Cosmos Seashells - Long Blooming Period in All Zones Cosmos Seashells - 1000 Seeds Approximately Easy to Grow Annual in All Zones, As the seeds do not need light to germinate, they can be sown directly or covered with 1/4 inch of soil. Sow your Cosmos seeds in the Full Sun to Partial Shade. As cosmos flowers are very adaptable, they can thrive in average to poor soil quality, and they are tolerant to dry conditions. Non GMO and Neonicotinoid Seed Marde Ross & Company has been a Licensed California Nursery Since 1985,