Add Harmony to your Garden with Cosmos


“Cosmos” is the Greek word for harmony or ordered universe and is directly opposite of “chaos,” which is how one might describe the riotous explosion of color these attractive flowers bring to the home landscape.

Close up of a bright pink cosmos flower.

Spanish priests in Mexico named these cheery little blooms because of their evenly placed, orderly petals.

Indeed, the plant’s pink, red, white, lavender, orange, or chocolate petals are beautifully spaced around a (usually) yellow central disk.

Growing Conditions

These plants belongs to the huge Asteraceae family, and are cousins of daisy and marigold. Of the 20 or so species of cosmos, two are most commonly grown in home gardens: C. sulphureus (sulphur and yellow cosmos, Mexican aster) and C. bipinnatus (common and garden cosmos and also – because, of course – Mexican aster).

White Cosmos |
Photo by Lorna Kring.

C. sulphureus is native to Mexico, Central America, and northern South America. It has naturalized in most other parts of the world. C. bipinnatus, also native to Mexico, has found its way into most corners of the globe, as well.

Sulfur Cosmos |

These pretty flowers liberally reseed – to the point where they are sometimes referred to as weeds. In the event that you have too many blooms, cut the flowers and put them in vases.

Hot, dry conditions, along with poor to average soil, are optimum conditions for this plant. Usually grown from seed, you may also find starts at a nursery.

How to Grow Cosmos |
Photo by Lorna Kring.

In most parts of the United States, this plant is considered an annual, though gardeners in zones 9 and 10 may find them to be perennial.

And with a long growing season, they add vibrant color to the autumn garden.

Tips for Growing Cosmos |

They also make a great choice for children’s gardens and novice gardeners thanks to their easy and quick growth habits.

Recommend Cultivars

You’ll find a wide variety of cultivars and mixtures available from seed suppliers. For a brilliant red, orange, and yellow collection of C. sulphureus, try this packet of 500 seeds from Mountain Valley Seed Co., available via True Leaf Market.

Cosmos Cosmic Mix |

Cosmos Cosmic Mix

These plants will reach about 12 inches tall and produce semi-double, 2- to 3-inch flowers that bloom throughout the season.

Or, choose classic cosmos in a rainbow of colors in this seed mix from David’s Garden Seeds, available via Amazon.

Crazy for Cosmos Mix

You’ll get 10 open-pollinated varieties in this mix of 500 seeds that will grow from 45 to 54 inches tall.

David’s Garden Seeds also offers a stunning deep red variety, also available on Amazon. ‘Tetra Versailles Red’ flowers open wine-red and gradually fade to a bright pink.

Cosmos ‘Tetra Versailles’ Seeds

You’ll get 500 non-GMO, hand-packed seeds that produce 2- to 3-foot plants that bloom in about 80 days.

Care and Maintenance

This low-maintenance plant tolerates fairly poor, well-drained soil with a pH between 6.0 and 8.5. You don’t want to fertilize much because you’ll end up with lots of foliage and not many flowers.

Sow seeds outdoors at a depth of 1/16 inch, or indoors five to six weeks before the expected date of last frost.

Grow Gorgeous Cosmos |
Photo by Lorna Kring.

These 1- to 6-foot-tall plants can become top heavy and floppy, so plant them in masses and they’ll support each other.

These cosmic gems flower best in full sun, but the plant will tolerate a bit of shade. It requires only a moderate amount of water.

Plant tall varieties at the back of borders or as a central focal point, and use smaller varieties as mid-sized plants in mixed beds.

A field of orange, pink, red, and white cosmos flowers in bloom.

For planters and containers, make sure to use dwarf varieties. Full sized specimens will crowd out the other plants, and their roots will dominate available soil.

Deadhead spent flowers to encourage more blooms, but leave some in place to develop seeds – they’re a favorite of visiting winter birds!

Pests and Diseases

This Asteraceae plant family member can be plagued by aphids and thrips.

For both of these pests, try insecticidal soap, such as this one from Garden Safe, available via Amazon.

Garden Safe Houseplant and Garden Insect Killer, 24-Ounce Spray

Also look out for aster yellows and powdery mildew.

The only cure for aster yellows is prevention. Use diatomaceous earth or insecticidal soap to kill the insects that spread the bacterial disease. Plants infected with aster yellows must be pulled up and destroyed.

Safer Brand Garden Fungicide, 24 Ounces

Treat powdery mildew with a fungicide, such as this one from Safer Brand, available via Amazon.

A Little Order, A Lot of Beauty

If your garden universe doesn’t include this worldly annual, perhaps it should. This easy-care plant thrives on sun and heat, offering glorious color in return.

Add Harmony to Your Garden with Cosmos |
Photo by Lorna Kring.

Look for seeds online, plant indoors a few weeks before the last freeze, or outdoors in early spring. Keep diatomaceous earth and insecticidal soap on hand and you’ll be set.

Cosmos Quick Reference Chart

Plant Type: Most are annuals, self-sowing Flower Color Var. including red, pink, orange, white
Native To: Mexico, Central America, Northern South America Tolerance: Drought (when mature)
Hardiness (USDA Zone): All Maintenance Minimal; slightly invasive
Bloom Time: Summer, early fall Soil Type: Loamy, poor to average soil
Exposure: Full sun Soil PH: 6.5-7 (neutral to slightly acidic)
Time to Maturity 55-100 days, depending on cultivar Soil Drainage: Well-draining
Spacing 4-6 seeds, thin to 20-24 inches Companion Planting: Makes an excellent trap crop for aphids
Planting Depth: 1/8 inch Uses: Borders, beds, containers, cut flowers
Height: 1 - 5 feet (depending on cultivar) Family: Asteraceae
Spread: 1-2 feet Genus: Cosmos
Water Needs: Moderate Species: Cosmos spp
Attracts: Birds, bees, butterflies
Pests & Diseases: Aphids, thrips, aster yellows, powdery mildew

Are cosmos growing in your garden? In the comments section below, tell us about your experience with this galactic favorite. And learn about another Asteraceae family member in this article about Swan River daisy.

Don’t forget to Pin It!

A collage of photos showing pink and orange cosmos flowers in bloom.

Photos by Lorna Kring, © Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Product photos via True Leaf Market, David’s Garden Seeds, Safer Brand, and Garden Safe. Uncredited photos: Shutterstock. With additional writing by Lorna Kring.

About Gretchen Heber

A former garden editor for a daily newspaper in Austin, Texas, Gretchen Heber goes through entirely too many pruners and garden gloves in a year’s time. She’s never met a succulent she didn’t like and gets really irritated every 3-4 years when Austin actually has a freeze cold enough to kill them. To Gretchen, nothing is more rewarding than a quick dash to the garden to pluck herbs to season the evening meal. And it’s definitely time for a happy dance when she’s able to beat the squirrels to the peaches, figs, or loquats.

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Jane Anderson
Jane Anderson (@guest_992)
3 years ago

Hello Gretchen, I love flower gardening. I always spend some time with my garden and family. I always teach my kids about gardening. You have such a beautiful garden. Thanks for sharing this post.

Elly (@guest_3637)
1 year ago

We recently moved and I planted cosmos for the first time this spring. I now have a few, dime-sized pink blooms. The plants are only 8″ tall or so. I’ve given them no care whatsoever in the corner of our garden and though they’re tiny, they are still pretty. In WA, I remember seeing large cosmos plants with 3″ blooms. Hopefully these bitty ones will grow a bit make it through the TX summer.

Allison Sidhu
Allison Sidhu (@allison-sidhu)
Noble Member
Reply to  Elly
1 year ago

These flowers do love hot and dry conditions, so they should do well in your area! Keep in mind that the size of the blooms is dependent on the cultivar- different varieties may grow to a range of different heights, with blooms of different sizes as well. If you love large blossoms, try the Cosmic Mix. The Apollo, Sensation, and Double Click series are also known for large blooms.

Jack (@guest_3938)
1 year ago

I love planting colorful flowers and I think they are very much perfect for the Spring season! 🙂

Mike Quinn
Mike Quinn (@mike20)
Active Member
Reply to  Jack
1 year ago

We’re with you there Jack! Thanks for reading.

Michelle (@guest_3982)
1 year ago

Great article! My cosmos are coming up again this year having reseeded all over the place. I am in no way upset about that. My first year growing them, they grew taller than the house. 7ft.+, those crazy, happy, cosmos.

Mike Quinn
Mike Quinn (@mike20)
Active Member
Reply to  Michelle
1 year ago

Hi Michelle! Sound beautiful and very cottage gardenish (my favorite ornamental style…I’ve been watching too much “Escape to the Country” via Britbox).

Do share some photos with us when they reach maturity! You can attach them to the comments using the little camera icon at the bottom of the comment box.

diane (@guest_9401)
Reply to  Michelle
3 months ago

Hi Michelle! Did you fertilize or add anything to them? I need some help getting them growing!

Sheri Davis
Sheri Davis (@guest_4355)
1 year ago

I have seeds and was unable to plant this last spring. The seeds are dated 2/19/19 will they be too old to plant next spring?

Apollo GT
Apollo GT (@guest_4444)
1 year ago

Thank you for your advice 😀 I am just now starting to collect these. wanted to mix them with marigold and coreopsis. you think it will be ok in the same pots?

Lynn (@guest_4539)
1 year ago

I have a hillside too steep to mow–a hill whose wild growth the butterflies love in the fall. I thought to plant cosmos there…will scattering seeds be enough to do that?

Richard warren
Richard warren (@guest_4677)
1 year ago

Hi I have Cosmos but the flower never seems to fully bloomed it turns like a brown black what causes that

Sandy (@guest_4748)
1 year ago

After 2 attempts with cosmos from store plants that failed, I started from seed this year. My plants are 3-4 feet tall with only 1 bloom😣. Thought maybe the needed more water as there is brown, dying foliage at the bottom and then have also fed them twice with Miracle Grow. And now I read that they do best without this. I live in Plano and want blooms now!! Soil here is more alkaline clay. Help!!

claire (@guest_4786)
1 year ago

This is my cosmos. I planted a packet of wildflowers and these appeared. They are nearly 5ft high now. Im hoping they come back next years as they really are beautiful and very colourful and make a lovely sight all over my border.

WP_20190807_12_20_17_Pro (2).jpg
Linda Baley
Linda Baley (@guest_4838)
1 year ago

We threw these seeds out in an area that was bare, not knowing what they would do or if they would grow. They have grown into tall, lavish flowers, the most beautiful flowers we’ve had! Super simple to grow and they grow abundantly! Love the Cosmos and will have them every year from now on!

Allison Sidhu
Allison Sidhu (@allison-sidhu)
Noble Member
Reply to  Linda Baley
1 year ago

Beautiful, Linda. Thanks for sharing!

Sharon (@guest_4979)
1 year ago

I planted a rabbit and deer resistant flower seed mix along the fence line of our large veggie garden last year. This year nearly everything came back and the cosmos are gorgeous!
The mix contained daisy, blanketed Susan, baby’s breath, alyssum, California poppies and more but the cosmos are spectacular and in full bloom on Sept 1st in So. Oregon garden which is visible from the street. Neighbors and passers by seem to live it as we are known as the “place with the big, beautiful garden.

Sarah Scott
Sarah Scott (@guest_4989)
1 year ago

Another wonderful use for orange and yellow Cosmos is as a natural dye, used with a mordant on natural fibers. The soft yellow color is beautiful!

Audrey (@guest_5055)
1 year ago

My Cosmos, I bought the seeds at a Dollar Tree not knowing what would appear because it was called a Spring Mix lol

Twila Wenger
Twila Wenger (@guest_5279)
Reply to  Audrey
1 year ago

Me too!! Hope they come back ❤️

Jennifer (@guest_5177)
1 year ago

I planted cosmos 3 years ago, last year they didn’t grow back. This year they have taken over!

daniel girard
daniel girard (@danielgirard242)
1 year ago

Hi, I started my first planting of wildflowers this past Spring. They all have done well. I’ve been anxiously waiting for the Cosmos to bloom (it’s the middle of October in Maine). Wondered if you knew what kind and colors these might be. Also, some are upwards of 6′ tall and some are 12″ or so tall.

Jade (@guest_5930)
8 months ago

I grew lovely cosmos last growing season. I did not pull them up from the ground because my said he was going to deal with the garden beds over winter.. he didn’t though. SO.. they look pretty awful now. all gangly and falling down ( dead). Should I pull them from the ground? I assume that there will be more natural pop up’s ( reseeds).



jessica (@guest_5968)
8 months ago

I have partial shade, but would love to know if there is a variety that is more shade-tolerant than others. Maybe sea-shells? It’s the only one I see listed in “part shade” annual seed mixes. Not sure whether it’s just because it’s readily available or because it’s actually more tolerant of shade than say, the yellow-sulfur varieties. Thanks!

Allison Sidhu
Allison Sidhu (@allison-sidhu)
Noble Member
Reply to  jessica
8 months ago

Where are you gardening, Jessica? Most types of cosmos appreciate some afternoon shade in hotter regions, though they are typically “full sun” plants. It’s very difficult to get them to bloom in the shade.

You’re right, though – I’m not sure about C. bipinnatus ‘Seashells,’ but some sources say C. sulphureus can thrive in less light, as well as being heat and drought tolerant. In Vol. 2 “Problems” of his series “What Grows Here? Favorite Plants for Better Yards” (available on Amazon), Jim Hole suggests the ‘Cosmic Orange’ cultivar.

Denise Barham-Hall
Denise Barham-Hall (@guest_6322)
7 months ago

Hi Gretchen,

I have just been given 12 Cosmos plants which are young seedlings about 4-6 inches tall on single thin stems topped with two layers of delicate leaves.

Do I need to pinch the top out to stimulate more growth low down, or will it develop more thickness as it grows? I am fearful they may droop when I come to plant them out.

Please advise, thanks.

Allison Sidhu
Allison Sidhu (@allison-sidhu)
Noble Member
Reply to  Denise Barham-Hall
7 months ago

Thanks for your question, Denise. Pinching seedlings back is recommended, to encourage bushy growth. Are these growing indoors? If you think there’s any chance that they may be growing leggy in an attempt to reach for the light, you might want to try adding a grow light to your setup to give them what they need in the seedling stage. When they grow a little more, maybe to 8 inches in height, pinch back the top 3-4 inches just above a set of leaves. Even when they are encouraged to develop a more sturdy, bushy form, cosmos may still require… Read more »

Jean Smith
Jean Smith (@guest_6638)
6 months ago

Cosmos have grown from seed to about 4cm high what do I do with them now?

Allison Sidhu
Allison Sidhu (@allison-sidhu)
Noble Member
Reply to  Jean Smith
6 months ago

Are you growing them in seed starting trays Jean, or small pots? Cosmos can be planted out any time after all danger of frost has passed. If you aren’t ready to plant them out yet, to make sure your seedlings have enough room to continue to grow, you can move them into 5-inch pots at this size, and continue caring for them indoors until they reach about 8 inches tall. At that point, you can pinch them back if you like, to encourage bushier growth. When you’re ready to transplant, harden them off for about a week, exposing them to… Read more »

Patrick E McClaugherty
Patrick E McClaugherty (@guest_7798)
6 months ago

Great info! Bought some Cosmos at Bloomers Garden Center in Elgin.

Patricia Beard
Patricia Beard (@guest_9399)
3 months ago

I have yellow and orange Cosmos. Some of the flowers are double. I have bought seeds for the past 2 years with pink and white Cosmos picture on the package but they are orange when they bloom. The butterflies really enjoy them. I just want some different colors.

Allison Sidhu
Allison Sidhu (@allison-sidhu)
Noble Member
Reply to  Patricia Beard
3 months ago

That’s too bad, Patricia. It sounds like they were mislabeled. But at least the pollinators are enjoying them!

We have a roundup of cosmos varieties in the works- stay tuned for suggestions this coming spring!

ira e goode
ira e goode (@guest_10424)
1 month ago

why does the bottom turn brown

Allison Sidhu
Allison Sidhu (@allison-sidhu)
Noble Member
Reply to  ira e goode
1 month ago

I’m not sure exactly what you mean, ira. When you say bottom are you referring to the foliage, the stems, or the blossoms? Can you share photos? We’d love to help you with this! Perhaps this is an issue with over or under-watering, or it may just be that the flowers are finished as we come to the end of the season.