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Are Cosmos Perennials? Increase Summer Bloom Time

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Prolific in bloom, cosmos can be a fantastic flowerbed stunner. Brilliant in color and magnets for pollinators, what’s not to love?! But, are cosmos perennials or annuals?

We’ve started growing cosmos back in our 2020 garden. After quite a few amazing seed swaps, I ended up with sensation cosmos and seashell cosmos.

Seashell cosmos flower with tubular petals
Seashell cosmos flower with tubular petals in our 2021 garden

At the time, I didn’t know if cosmos are perennials or annuals.

Now that I’ve grown them and familiarized myself, I can talk about cosmos for days!

What is the scientific name for cosmos flowers?

Cosmos flowers are scientifically known as Cosmos bipinnatus or Cosmos sulphureus. Cosmos sulphureus (sulphur cosmos and yellow cosmos) most commonly flower in shades of yellow and orange (or even red). Sometimes called garden cosmos and also Mexican aster, Cosmos bipinnatus brighten flower beds with hues of pink, purple, maroon, and white, with many other variations.

Pale purple pink cosmos - are cosmos perennials?
Pale purple pink cosmos in our 2021 garden – are cosmos perennials?

Are cosmos perennials?

Most popular varieties of cosmos are not perennials as they are not winter hardy. Gardeners generally treat cosmos as an annual flower and plant new plants each year. Also, tuberous cosmos, cosmos atrosanguineus, can be treated as a perennial with proper care.

Moreover, cosmos often drop seeds and end up reseeding themselves, which may give the illusion of a perennial plant.

Fuchsia purple colored cosmos flower
Fuchsia purple colored cosmos flower from our 2021 garden

Do perennial cosmos exist?

Yes, sort of. Chocolate cosmos are considered tender perennials with a tuberous root that requires care much like dahlia tubers. Native to Mexico, chocolate cosmos dazzle gardeners with their chocolatey scent and deep crimson coloring.

Do cosmos reseed themselves?

Yes, cosmos flowers readily reseed themselves! Whether by the wind, animals like bird swiping seeds, or another force in nature, cosmos often drop seeds that readily sprout the next year.

Fancy Cosmos flower with dark maroon and white / light pink
Fancy Cosmos flower with dark maroon and white / light pink in our 2021 garden

Tips to Extending Cosmos Bloom Time

If you want to grow cosmos and enjoy endless summer blooms, try some of these quick and easy tips!

  • Plant cosmos seeds indoors before frost to jump start your plants.
  • Pinch cosmos and plant the tops for double the plants and blooms!
  • Deadhead cosmos or cut fresh flowers to increase blooming.
  • Save seeds every year to grow even more cosmos in the new season.
  • Share cosmos seeds with your neighbors so you can all enjoy color everywhere!
Maroon red cosmos flower in our 2021 garden
Maroon red cosmos flower in our 2021 garden

Final Thoughts: Are cosmos annuals or perennials?

While we’d love for cosmos to live forever, we’ve answered the question – are cosmos annuals or perennials – with a slightly disappointed “annuals” for most and a delighted “tender perennials” for chocolate cosmos!

Either way, isn’t it fun planting cosmos from seed like Apricot Lemonade Cosmos?! Or buying new flowers to plant every year?!

Cosmos hail from the same family as daisies and sunflowers, Asteraceae. They make lovely cut flowers and they’re very easy to grow.

Side profile of a cosmos flower
Side profile of a cosmos flower in our 2021 garden

If you aren’t already growing cosmos in your garden, I highly recommend them. They’re prolific bloomers and require little care in my experience.

(Of course, you can deadhead them or pinch cosmos to create more compact plants if you like.)

Sorry to burst the bubble that cosmos aren’t perennial, but I hope you’ll try growing them anyway! They’re among one of my favorites like zinnias and sunflowers.

Lots of purple cosmos flowers in our 2021 garden
Lots of purple cosmos flowers in our 2021 garden

Let us know if you have any questions about cosmos or any fun stories to share about growing them in your own garden! We always love hearing from gardeners who share our love of planting and caring for gorgeous flowers.

Happy Gardening!

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