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How to Plant Cosmos Seeds – Easy, Beautiful Cutting Flowers

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Cosmos are one of the easiest flowers to grow! We learned how to plant cosmos seeds several years ago and haven’t stopped since. Dazzled by the beautiful and prolific blooms, we grow cosmos from seed and enjoy cut flowers all summer long!

Holding a pinch of cosmo seeds above the seed packets
Lots of different Cosmo flower varieties to grow!

Cosmos make a great choice for your garden. Learn the easiest tips for planting cosmos seeds indoors or direct sowing!

Retail store seed rack with selection of Cosmos
Retail store seed rack with selection of Cosmos

Growing Cosmos from Seed

Growing cosmos from seed is so easy and it’s a wonderful child-friendly gardening activity, too. It’s so rewarding to teach them how to plant cosmo seeds indoors or direct sowing outdoors.

Cosmo flowers produce profuse blooms that kids will love to pick or cut during the summertime.

Planting Cosmos seeds in egg carton with soil
Planting seeds from cosmo flowers in an egg carton with soil

I love harvesting cosmos seeds so we can grow these pretty flowers again the next season! Check my post on saving the seeds to try it yourself.

How to Plant Cosmos Seeds Indoors

If you want to get a jump on things, start your flower seeds indoors. Get your kids involved in this fun and easy gardening activity.

  1. Cut the top off of an egg carton.
  2. Turn the bottom upside-down and poke holes in each of the egg compartments.
  3. Place the bottom of the egg carton on top of the lid, like a tray.
  4. Fill all of the egg carton cavities with potting soil.
  5. Select your seeds and decide how many seed cells you would like to fill.
  6. Place two to four seeds per seed cell. (I find cosmos seedlings fairly easy to separate and very forgiving during potting up and transplant.)
    • Tip: I practically surface sow these guys with great results! I basically scratch them in just like zinnias, just a little bit of potting soil dusted on top or around the edges of the seeds.
  7. Write directly on the egg carton to label the type of cosmos you planted. (You can also write on masking tape, a popsicle stick, or plastic plant tags.)
  8. Spray with a water spray bottle or mister to wet the soil.
  9. Keep the soil moist and check daily for growth and watering needs.

Cosmos generally germinate pretty quickly. In most cases, your little ones should enjoy that first peek of green within less than a week!

Holding Cosmo flower seeds in the sun
Handful of cosmos flower seeds leading into our 2021 garden

Direct Sowing Cosmos from Seed

Cosmos readily reseed themselves, growing new plants where seeds dropped in the previous season.

You can easily direct sow cosmos from seed outside in your garden spaces. Follow these simple tips to plant directly outside.

  1. Choose a sunny spot in your garden with a little room for the plants to spread out. For spacing, leave 12 to 18 inches between seeds or plan to thin them later.
  2. Surface sow or cover the seeds with only a light dusting of soil, no more than 1/4 inch deep. Cosmos need light to germinate!
  3. Water adequately to help the seeds germinate.
  4. Check back frequently for signs of growth.
  5. Continue to care for the seeds and seedlings as they grow.
Getting ready to direct sow cosmo seeds - hand holding many seeds
Getting ready to direct sow some Cosmos!

Cosmos Seedlings

Cosmo seedlings seem to grow rather quickly in my experience. I love watching them grow and look forward to seeing the flowers that bloom!

Each year, I usually find some volunteers in the garden from the previous year’s seeds that dropped. It’s fun to see what colors emerge when they bloom!

Cosmos seedling growing in rocky clay soil
Cosmos seedling growing in our rocky clay soil

This seedling above is a cosmo volunteer that popped up from a dropped seed from last year’s flowers.

Time Lapse Video of Cosmos Seedlings Growing!

Here’s a short time-lapse video of seedlings growing from the seeds!

Pro Tip on Growing Cosmos

By the way, consider pinching off the growing tip on your cosmos seedlings when you transplant them outside or as they grow naturally out there. The plants should respond by growing bushier and a bit more compact.

Our very first cosmos flowers grew very large and sprawling – they really were too out of control. I much prefer the bushier habit with many more blooms!

Tall purple and pinkish lavender cosmos in our 2021 garden
Tall purple and pinkish lavender cosmos in our 2021 garden

Issues and Pests for Cosmos

According to the Utah State University Lawn and Garden Extension, cosmos don’t face many problems in the garden. In fact, their biggest issue is likely their robust nature in reseeding themselves! (And to some gardeners, this is more of a blessing than a curse!)

Still, the NC State Extension mentions powdery mildew, gray mold, stem canker, and aphids as issues common to cosmos.


Yes, cosmos flower seeds grow quickly and according to Farmer’s Almanac, they bloom in about 7 weeks. If you plant cosmo flowers from seed in June, you can most likely expect blooms by the end of July or sometime in August.

You may be able to plant seeds for cosmos in the fall if your first expected frost date is far enough away. Cosmos tend to bloom fairly quickly, so if you have more than 8 weeks until frost, it’s worth a shot. You can also plant the seeds in a container that you can bring inside on chilly nights to prolong the growing season.

Some cosmos grow to be 5 feet tall! Others may grow closer to 3 feet tall and dwarf cosmos may only grow to be 18 inches or 2 feet tall. Consider the height of your cosmos when choosing where to plant them.

Generally speaking, cosmos can grow between one and five feet high, depending on type.

Our cosmos the past few years have grown as tall as I am – five feet two inches!

Aim for spacing of 12 to 18 inches when starting seeds. The plants produce many branches with flowers, so give them ample room to grow. You can space dwarf cosmos closer together, about 8 to 10 inches apart, since they are smaller.

Cosmos growing tall and reaching toward the sun
Pale pinkish purple Cosmos growing tall and reaching toward the sun

Final Thoughts: Planting Cosmos Flower Seeds

Growing cosmos from seed will be a part of our garden plan for a long time to come. We found so many benefits growing these pretty flowers from seed.

In 2020, we didn’t even plant our flower seeds until June! We received some seeds for cosmos in a swap and happily grew seashell and sensation varieties the first year.

When they bloomed, we enjoyed lovely shades of purple, pink, and wine, along with pure white ones. The petals of the seashell cosmos had a tubular appearance.

Since then, I’ve also tried Bright Lights mixed cosmos. The gold / yellow cosmos we grew became some of my favorites!

Now we are growing even more kinds since we loved them so much!

They work out great for bouquets and the blooms are plentiful per plant.

Various different seed packets of cosmos flowers - Bright Lights, Daydream, Picoti, and more
Various different seed packets of cosmos flowers – Bright Lights, Daydream, Picoti, and more

Favorite Cosmos So Far

Here’s what we’ve planted so far:

  • Apricot Lemonade Cosmos – from Swallowtail Garden Seeds (You can also get them at Etsy!)
    Apricot Lemonade Cosmos, Available for sale on Etsy - Photo courtesy of the seller, MossHallSeeds (https://tidd.ly/3coO5YJ)
    Apricot Lemonade Cosmos, Available for sale on Etsy – Photo courtesy of the seller, MossHallSeeds.
  • Cosmic Orange Cosmos from our seed swap friend Jenny on Instagram
    Cosmic Orange Cosmos, available for sale on Etsy at RobinSeeds - https://tidd.ly/3x0FvHl (Photo courtesy of RobinSeeds.)
    Cosmic Orange Cosmos, available for sale on Etsy at RobinSeeds – (Photo courtesy of RobinSeeds.)
  • Cosmos Picoti – white cosmos with a dark pink edge we bought from Nikitovka Seeds online
    Beautiful cosmos picotee flowering with white petals and pinkish purple edges. Available for sale at Etsy - photo courtesy of seller, ZellajakeFarmGarden. https://tidd.ly/3z5hWPu
    Beautiful cosmos picotee flowering with white petals and pinkish purple edges. Available for sale at Etsy – photo courtesy of seller, ZellajakeFarmGarden.
  • Daydream Cosmos – from a swap within a Facebook seed swap group with Jamie C.
    Daydream Cosmos Seeds - beautiful white with pink and yellow centers, available for sale on Etsy. Photo courtesy of seller, DaisyHeader. https://tidd.ly/3iikcgp
    Daydream Cosmos – beautiful white with pink and yellow centers, available for sale on Etsy. Photo courtesy of seller, DaisyHeader.
  • Seeds we saved from 2020 – can’t wait to see if they’re hybrids or what!

We also decided to plant some Bright Lights, which are yellow, orange, and red cosmo seeds, according to the packet.

You can check out a pretty good overview of some popular cosmos varieties at the Aggie Horticulture® AgriLIFE Extension Texas A&M System.

Bright Lights Cosmos - yellow and orange flowers in our 2022 flower garden
Bright Lights Cosmos – yellow and orange flowers with seed heads in the background in our 2022 flower garden

Benefits of Planting Cosmos

Attractive to people and pollinators alike, cosmo flowers are a pretty, low-maintenance bloom with many benefits.

  • Enjoy cut flowers all season long!
  • Attract pollinators to your garden.
  • Add beautiful, long-lasting color to your garden and outdoor spaces.
  • Relax with a flower that doesn’t require much maintenance.

You can find different seeds for sale at plenty of retailers!

Are you growing cosmos for the first time this year? Or maybe you are a long-time grower of this beautiful flower! Let’s chat all about cosmos in the comments – what’s your favorite type of Cosmo flower?

04.23.23 – Updated to add FAQ section. Added spacing, bolded headings, marked links as sponsored if needed. Added more photos and resized to full size and added video. New date for comprehensive update from May 4, 2021. Added extension sources.

06.08.23 – Updated to add link to saving seeds post.

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  1. I have a love hate relationship with cosmos. I wasn’t warned how prolific they are and the first year they kept reseeding and took over an entire flowerbed. The seeds blew into neighbors yards and they had cosmos. Mine also grew to over 5 ft tall but were trampled by a Texas rain storm. Then they looked horrible.
    I’ve learned to pinch them back before they bloom and to dead head before they reseed.
    You can count on cosmos returning each year and I’ve learned to appreciate their efforts to remain in my garden.
    My neighbors constantly compliment the cosmos more than any other of the other flowers.

    1. Hi Steven! Thanks so much for your thoughtful comment – I too was very surprised last week to see several cosmos have reseeded themselves!
      I thought my daughters and I meticulously saved every seed head, but it turns out we got a few surprises!
      (Although, I can imagine taking over an entire garden would be quite a different scenario! I am still trying to decide where to plant all of our flowers this year. 🙂
      Did any of yours cross to form different colors or features from the parents? We are excited to see what we end up with!
      Our 4 o’clocks also had a few volunteers this year and I am equally excited to see if they crossed or will resemble the original plant where the seeds must’ve dropped.

      Deadheading cosmos and Pinching are excellent ideas – I saw photos from a gardening friend of mine where she was able to double propagate her cosmos seedlings by pinching and replanting the top few inches of the plants. She placed them under grow lights and they grew a beautiful new root system! I definitely plan to try this on any flowers that I pinch this year. (It sounds like you already have plenty to spare! But this sounds like a fun experiment to try if you have other flowers you wish to multiply.)

  2. I was smitten by Cosmos when my very first exposure was to a 2 acre roadside field! I began searching for seedlings at my local greenhouses and nurseries. When I innocently inquired about Cosmos daisies, I was emphatically informed that they are NOT daisies, simply Cosmos! That’s the moment that I realized that they were indeed highly regarded by professionals and commoners (like myself) as well. I am so influenced by Cosmos that I actually wear an original, colorful tattoo that has had hundreds of compliments over the years. Long Live Cosmos!!!

    1. Hi Lisa! That’s sounds like such a wonderful tribute to the Cosmos Flower! Thanks for sharing your story – I love the origin stories with meaningful reasons about how a flower or plant gained its significance for someone. 🙁 I have a friend on Instagram who grows an entire field of Cosmic Orange Cosmos and has people come for the flower experience – photos, bouquets, etc. She sent us some seeds and I can’t wait to see how beautiful these orange ones are! The Cosmos really brightened up our backyard last year and I can’t wait to see what they do this year, since we got a few volunteers in the same garden bed! 🙂 I also love how easy they are to grow with my kids!

  3. Thank you for sharing valuable information about the cosmos. I love reading your article that gives additional knowledge about plants. Keep sharing more articles like this.

    1. Hi Nat! Thanks for stopping by – I hope they are beautiful for you! Hey, you never know – growing cosmos in pots could still work out fine! (I grew zinnias in pots last year.) Or you can always transplant them to the ground if you find you have a better place for them. Wishing you much success in the garden!

    1. Hi Becky! Your hobby sound very cool! I got my original cosmos from a seed swap group on Facebook, I think it was the Great American Seed Swap or similar. However, I have also seen cosmos seeds for sale on those seed racks at Lidl for example or another store, as well as online. If you wanted to send me a SASE, I can definitely send you some, but can’t guarantee what color my saved cosmo seeds will turn out to be. Hope you can grow and enjoy them too! They reseed for many years to come. 🙂

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