Cosmos Seeds,
Double Dutch Rose

Cosmos should be planted only after the last frost, once the soil temperature is consistently at least 60 F for proper germination. Since cosmos are not frost-hardy, check your local area’s last frost date before planting. The plant grows quickly and typically starts blooming 60-90 days after sowing, with flowers appearing from midsummer until the first frost. If you’re uncertain about your frost-free dates, check out our blog post, ‘Our Experts Answer Questions, Share Resources.’

Cosmos seeds can be directly sown outdoors after the last frost or started indoors 3-4 weeks before transplanting. Sow seeds 1/8-1/4 inch deep, as they need light to germinate. Space plants about 10 inches to give them enough room for good airflow and healthy growth. Water lightly during germination, which typically takes 7-14 days. Choose a location with at least 6-8 hours of full sun daily for the best flowering results.

Double Dutch Rose cosmos thrives in well-draining, light soil and requires very little maintenance. It prefers moderate watering, so allow the soil to dry out between waterings to prevent weak, leggy growth. Avoid over-fertilizing, as too much nitrogen will encourage leafy growth instead of flowers. Taller plants may need staking in windy areas. For a longer blooming period, deadhead spent flowers regularly. This will encourage continuous blooms until the first frost.

• Cosmos are insect pollinated, and there may be some crossing between varieties in the garden. You can enjoy the mixing or use caging techniques and hand pollination to avoid crossing.
• Saving seeds from cosmos is easy: simply allow the heads to brown and dry on plants and collect seeds. Store in a cool, dry, dark place over winter.