How to Plant Cosmos Seeds

Of the 20 species of cosmos, two varieties, Cosmos sulphureus and Cosmos bipinnatus, are most frequently planted in flower gardens. This annual flower grows up to 7 feet tall, making it an ideal flower for the back of flower gardens or along tall fences. Cosmos make great cut flower additions to fresh floral arrangements and can also be dried. Cosmos are simple to grow and have low-maintenance needs when it comes to moisture and feeding.

Rake the garden soil to break up large, hard chunks of soil and loosen the dirt. Choose a sunny, well-drained location where cosmos will thrive.

Sprinkle the cosmos seeds onto the surface of the soil where you want them to grow. Slowly rake back and forth with the garden rake to sow the cosmos seeds. Since the planting depth for tiny cosmos seeds is 1/16-inch, raking the seeds into the soil will plant them at the proper depth.

Water the cosmos seeds. Wet the seed bed thoroughly, then allow the water to be absorbed into the loose soil.


Sow cosmos seeds in early spring. Unlike many seedlings, cosmos do not need to be thinned as they grow. Make sure cosmos receive sun for eight to 10 hours per day. Cosmos are drought-tolerant and do well with occasional thorough waterings, rather than daily waterings.


Cosmos do not require a lot of plant food. Too much fertilisation results in more foliage growth and fewer flowers.

Things You'll Need

  • Garden rake
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About the Author

Mary Ylisela is a former teacher with a Bachelor of Arts in elementary education and mathematics. She has been a writer since 1996, specializing in business, fitness and education. Prior to teaching, Ylisela worked as a certified fitness instructor and a small-business owner.