Harvesting Cosmos Seeds – 10 Quick Tips on Collecting & Storing

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Do you love seeing the beautiful flowers in your garden staring back at you every day? I sure do! I especially love the ones that keep on blooming all season long, like Cosmos flowers. Try harvesting cosmos seeds so you can effortlessly grow these pretty flowers year after year!

Finger pressing on ripe seed head from Cosmic orange cosmos flower over a red cup for collecting seeds
Harvesting Cosmos Seeds with my favorite quick and easy method! Photo features Cosmic Orange Cosmos, which are super easy for seed saving!

Before you learn how to harvest cosmos seeds, it can be helpful to check out your plants and look for some dried seed heads. Also, take note of what the cosmos seeds look like.

What Do Cosmos Seeds Look Like?

Cosmo flower seeds look like small, pointy sticks that are slightly curved with tapered, pointed ends. They are generally dark brown in color and may be thin or slightly thicker in girth.

Some cosmo flowers produce seeds that are longer while others produce shorter seeds. Generally speaking, cosmos will germinate readily from healthy seeds.

Lots of Cosmos Seeds on a piece of construction paper
Lots of Cosmos Seeds on a piece of construction paper

Before you can harvest the seeds, it helps to know what they look like. Refer back to this post and the photos if you aren’t sure!

Harvesting Cosmos Seeds

When cosmos produce seed heads, you can wait for them to dry and then snip them off to save the seeds.

Once I read that the first blooms to go to seed contain the most seeds, and I paid attention in my garden enough to believe this is true.

We did, in fact, find larger, nicer and more seeds inside the dried, spent blooms that finished up first.

So be sure to collect those early seed heads first, if nothing else!

Cup of seeds from cosmo flowers
Cup of seeds from cosmo flowers

How to Harvest Cosmos Seeds

Here are some tips on how to harvest cosmos seeds:

  1. Wait until the bloom is fully spent. It may take on a shade of brown.
  2. Use scissors to snip off the old bloom above the last set of leaves. You can also simply pull the seeds off of the seed head with some varieties, like Cosmic Orange Cosmos.
  3. Drop the seeds into a plastic cup or a paper bag.
  4. Continue to collect spent blooms so you can save many seeds.
  5. Pull the spent cosmos flowers apart over a paper plate, tray, or lid to reveal the seeds. Watch out for caterpillars and other pests or problems.
  6. Save the seeds in a paper envelope or paper lunch bag until you are ready to trade them or plant them in the future. You can also try other seed storage ideas!
Cosmos seeds in a cup with a name tag next to pretty orange cosmos flower
Saving cosmos seeds from Cosmic orange variety in our 2022 garden

Saving Seeds: Special Precautions

When collecting cosmos seeds, follow a few precautions to increase your chances of successful seed saving.

  1. Make sure the flower heads are completely dry. Harvesting cosmos seeds only after they are fully dry helps to prevent mold or fungal growth during storage.
  2. Check for pests / insects. Sometimes tiny caterpillars may hang out on the dead flower heads. Inspect seed heads for these guys and remove them!
  3. Plan around the weather. Avoid harvesting seeds on damp or rainy days, because the moisture can reduce seed viability or may even cause seeds to sprout early. Always handle seeds with care, using clean, dry hands to prevent contamination.
  4. Save seeds in breathable packages if you aren’t sure. Better safe than sorry! Store cosmos seeds in paper envelopes or similar if moisture could be an issue.
Waxed glassine envelope used to store seeds from seashell cosmos
Waxed glassine envelope used to store seeds from seashell cosmos from our garden.
Note the difference in the seed pod compared to the cosmic orange cosmos!

When to Harvest Cosmos Seeds

Make the most of your cosmos flowers by saving seeds for swaps or next season.

The best time to harvest cosmos seeds is once the seed heads turn fully brown and dry. This timing can vary depending on where you live and when you planted your cosmos plants.

Mid to late summer through the fall is a good target for collecting seeds from cosmos.


Yes, it is easy to save seeds from cosmos flowers for next season! Simply remove the seeds from the spent flower heads before they drop to the ground.

Saving seeds from cosmos flowers makes it easy to preserve your favorite varieties while also saving money on buying new seeds. You can also maintain the genetic diversity of these lovely flowers.

When you want to harvest seeds from cosmos, wait until the flower heads completely dry out on the plant. After the petals fall off, the center of the flower head will appear elongated, brown and dry. You will notice these brown seed heads shortly after peak blooming time on your plants, toward the late summer and autumn, but you may find some earlier in the summer as well.

Mature cosmos seeds are typically dark brown or black in color, with a nice thickness and a hard, dry texture. If the seeds are still green, flimsy, or soft, they are not yet mature and may not germinate successfully.

To collect cosmos seeds, you can simply snip off the dried flower heads using scissors or pruners. Place the flower heads in a paper bag or envelope to catch any loose seeds that might also fall out. Label the bag with the date and type of flower. Also, make sure the flower heads are totally dry before storing them.

You can also save cosmos seeds by removing just the seeds from the seed head. Seed heads from some cosmos varieties, like Cosmic Orange Cosmos, may erupt outward in a display that resembles fireworks. These seeds are easy to collect in one hand before dropping into a paper bag or cup.

Store cosmos seeds in a cool, dry place away from direct sunlight. Our preferred seed storage location is in a plastic photo storage box that we keep in the basement. You can use paper bags, small envelopes, or small jars with airtight lids to keep the seeds safe, only using jars if your are totally sure they are completely dry. Label each bag, envelope, or container with the variety and date of collection for easy identification later on.

Cosmos seeds can remain viable for approximately 2 to 3 years if stored properly. However, you should note that germination rates may decline over time, so it’s best to use the seeds within the first year or so for best results.

Lots of seeds bursting from orange cosmos seed pods in our garden
Lots of seeds bursting from orange cosmos seed pods in our garden

Cosmos Seed Harvesting

After learning how to collect cosmos seeds, I w1ish you a prolific cut flower garden for many years to come!

Keep in mind that the seeds you save may produce different flowers than the parents you saved them from.

This is because pollen can transfer between different flowers, creating hybrids. Hybrids may carry traits of both parents but resemble neither identically.

When harvesting cosmos seeds, you can label the packets or containers to the best of your knowledge and pay attention to the new flowers that bloom next time around.

Also, try to make sure you collect brown seed pods for the most part. Green seeds may be viable, but it’s much easier to bank on the brown seed heads having mature seeds inside.

Orange cosmo flower and green seed head that is working on ripening the seeds. Wait a bit longer to harvest this one!
Orange cosmo flower and green seed head that is working on ripening the seeds, photographed in our 2022 garden. Wait a bit longer to harvest this one!

Do you have any tips or tricks for harvesting cosmos seeds? Feel free to ask questions or share advice and fun anecdotes in the comments below. We love hearing from you!

Happy Gardening!

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