Attract more pollinators to your yard with colorful, nectar-rich cosmos flowers. Learn how to grow cosmos and which cultivars to try.
How to Grow Cosmos Flowers
Cosmos flowers do particularly well in lean soil. Some shorter varieties thrive in containers. It’s best to plant them just before the last spring frost, in full sun and in well-draining soil. Protect the flowers from strong winds, and consider harvesting seeds in fall to replant cosmos in different locations when spring arrives again.
Did you know you can direct sow cosmos seeds? Find out what that means—and how to do it.
If you grow your own food in the garden, you might plant cosmos there, too. Since cosmos is known to draw pollinators, it’ll improve the pollination for your flowering fruits and veggies (like strawberries, pumpkins and zucchini) and reward you with a larger crop.
- Common name: Cosmos
- Scientific name: Cosmos bipinnatus
- Attracts: Birds, bees, butterflies
- Zones: Annual
- Light needs: Full sun
- Size: 1 to 6 feet tall
- Grown for: Big, colorful blooms
- Foliage: Feathery leaves
Did you know—Fall is the best time to plant poppy flower seeds.
When Do Cosmos Flowers Bloom?
“I have a cosmos that I planted in a large pot. It grew all summer until the stem was over 10 feet tall, and the flower didn’t bloom until fall. Why did it get so tall and take so long to bloom?” asks reader Brenda East of Brunswick, New Jersey.
Horticultural expert Melinda Myers says, “Most Cosmos bipinnatus varieties grow between 1 and 6 feet tall, but it is not uncommon to find some growing much taller, such as yours. It does takes these cosmos 10 to 12 weeks to go from seed to bloom. Since the plant was putting all its energy into growing taller, it may have further delayed the onset of flowers.
Overfertilizing the plants, especially with high nitrogen fertilizers, promotes leaf and stem growth and can delay or inhibit flowering. Next year, try starting the plants indoors or purchase transplants for earlier blooms. Or just think of the late bloomers as added beauty in the fall garden.”
Pollinators Love Cosmos Flowers
All growing season long, bees and butterflies are drawn to cosmos flowers, which are nectar-filled, colorful and pinwheel-shaped.
Grow single or double cultivars of this easygoing bloomer, and they will produce gorgeous flowers and seeds for your feathered friends from summer through late fall. A classic garden annual, cosmos flowers are a great choice for bare patches in perennial beds. Plus, because cosmos is self-seeding, it saves you money on your garden.
If you’re lucky, you might even wind up with a monarch chrysalis on your cosmos plant, as one reader did!
“I discovered this handsome monarch chrysalis on a cosmos plant in my flower garden. I have lots of milkweed plants growing nearby for caterpillars to munch on, so this one must have ventured over to this plant to start the next phase of its life cycle,” says Birds & Blooms reader Brenda Doherty.
Want more buzz in your garden? Plant the best flowers to attract bees.
Cosmos Flower Cultivars to Try
Psyche White has jagged semi-double blooms that last all summer. Sea Shells features multi-colored flowers with petals shaped like tubes. Lemonade offers light yellow petals with white centers. And chocolate cosmos smells like chocolate!
Next, check out more butterfly flowers that are easy to grow from seed.
About the Expert
Melinda Myers is the official gardening expert for Birds & Blooms. She is a TV/radio host, author and columnist who has written more than 20 gardening books. Melinda earned a master’s degree in horticulture from the University of Wisconsin-Madison.
