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Discover how to grow cosmos from seed with our comprehensive guide, from sowing to blooming to saving the seeds for next year!

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Cosmos are an easily seeded flower that make the perfect backdrop for a garden. Plant the seeds and watch them come back year after year with beautiful delicate colors.

Cosmos varieties

There is a cosmos variety for any type of gardener. The cosmos bipinnatus has beautiful daisy like petals and the cosmos atrosanguineus sets off a delicious chocolate scent into the air.

When to plant

If you seed indoors start about 4 weeks before the last frost of your season. If you plan to direct sow the seed into the ground, it will germinate best between 60 and 80 degrees.

Starting seeds

For indoors, grab a seed tray and plant the seeds 1/4 inch into moist but not soggy soil. For outdoors, sprinkle the seeds on soil that is at least 65 degrees. Cover the sprinkled seeds with about 1/8 inch of soil.


After the cosmos have been established they are fairly drought-tolerant. Overwatering can actually cause them to decrease flowering.


Cosmos are not heavy feeders and too much fertilizer can limit blooms, but increase foliage. You may be able to skip fertilizer, but if you add fertilizer use a light amount of all-purpose fertilizer.


It isn't necessary to prune the cosmos, but pruning can encourage new growth. Deadheading spent blooms will help to prolong the blooming period.

Learn more about growing Cosmos from seed by clicking the link below!