Cosmos are annuals, grown for their showy flowers. The flowerheads may be bowl– or open cup–shaped and are atop of long stems. Cosmos are easy to grow and make good border or container plants. They make for good decorations in flower arrangements and also attract birds, bees, and butterflies to your garden.

Sun Exposure: 

Full Sun

Soil Type: 


Flower Color: 


Bloom Time: 


Special Features: 

Attracts Butterflies
Attracts Birds

Botanical Name: 


Plant Type: 



  • If you want a head start, you can plant cosmos indoors 4 to 6 weeks before the last spring frost in trays or pots with a good seed-starting mixture. Seedlings grow fast, so move them into 5-inch pots as soon as they're 3 or 4 inches tall.
  • Plant seeds in moist, well-drained soil about ¼-inch deep and 12–18 inches apart after the danger of frost has passed. You can also plant transplants instead of seeds. They also like soil that is not too rich.
  • They can tolerate warm, dry weather.
  • Depending on the type of flower, cosmos can grow anywhere between 18–60 inches tall.
  • If you are growing cosmos from seeds, be mindful that it takes about 7 weeks to first bloom. After that, though, your flowers should continue to bloom until the next frost.


  • In order to prolong flowering, you should deadhead the plants (remove the dead/faded flowers).
  • Because some of these plants can grow really tall, staking may be necessary.
  • Water regularly, but make sure you don't over-water the plants. Over-watering and over-fertilization can lead to plants with fewer flowers.
  • Cosmos beds may become weedy due to the fact that they self-seed, so remember to check them.



  • To harvest more seeds, remember to leave a few flowers on the plant because they will self-seed.
  • You can cut the flowers off anytime after blooming, but it's best to pick some right when the petals have opened.
  • If you cut the blossoms on good stems when they first open, they'll last more than a week in water.


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I want to know may I plant

I want to know may I plant the plant of cosmos now?

We're not sure where you

We're not sure where you live, but probably not. As written above, cosmos are best planted in the spring and need 7 weeks to grow, and will not survive the first fall frost.

Hi, I grow my Cosmos in

Hi, I grow my Cosmos in planters and was wondering with winter coming how I should care for them so that they may grow back in the spring. It gets quite cold here in Indiana so I am concerned. Thanks!!

Hi Jane, Cosmos are annuals

Hi Jane,
Cosmos are annuals and will not survive the winter. It's best to start with fresh seed next spring. You can collect the seeds from your cosmos at the end of summer. Make sure the seeds are dry and save them in an envelope or jar.

I love cosmos and they always

I love cosmos and they always do well. Do only the orange ones have the seed heads that can be pulled off? I've gotten other colors and they don't seem to have the dried seeds to pull off like the orange ones, wondering how to know which varieties has the dried seeds heads. I can't seem to find the answer anywhere online. Thank you

Most cosmos varieties develop

Most cosmos varieties develop seedheads if you leave the faded flowers on the plants. The seedheads may look a little different but you'll be able to see and collect the seeds after they have dried.

the stem of a Cosmos plant

the stem of a Cosmos plant broke, I buried the entire stem, will the stem grow new roots ?

I have about 10 cosmos' in a

I have about 10 cosmos' in a large raised bed, they were grown from seed in a greenhouse and planted out mid June, it's now mid August and I don't have any buds or flowers. They are nearly 4ft high and still growing. Do i need to do something to help them bud. They are in full sun. Thanks

Hi, Vicki, It sounds like the

Hi, Vicki, It sounds like the soil that your cosmos is in may be too rich, possiblyl especially heavy with nitrogen. For example, if you fertillize with a 20-20-20 (nitrogen, phosphorus, and potassium) the balance may be too much of a good thing. Nitrogen promotes leave growth. In future, you might try tomato fertilizer, a blend that promotes fruit (don't expect tomatoes to form on your cosmos; it's just that the blend of ingredients provides less nitrogen than the 20-20-20.)
They like sun, and it sounds like you're giving them plenty.
We hope this helps!

Thank you that does help. I

Thank you that does help. I am just impatient for them to flower. They do look lovely and healthy though.

Mine also took until the

Mine also took until the beginning of Sept. To bloom, but I started them a little late from seeds. This is great info, thank you

I have a Cosmo that I planted

I have a Cosmo that I planted at the end of May, not from seed though. It continues to grow in height, but there still is no sign of flowers getting ready to bloom. Why?

Cosmos usually take a long

Cosmos usually take a long time to grow the stem and leaves before the buds show. You should see some flowers soon. Remember to dead head the faded flowers to have more buds and flowers through the end of summer.

I have cosmos in containers

I have cosmos in containers on the deck & while the plants are growing well, the original hot pink coloris all washed out. They are a pinkish gray or dull looking pink. I bought these as sedlings at a nursery in a 4-pak. What blooms they had at the time were very vibrant. Is it not enough sun? Most of the sun is indirect, with the strongest & most direct sun after 2 p.m.

The flowers on my cosmos are

The flowers on my cosmos are getting smaller. What am I doing wrong? Thank you!

Cosmost likes full sun. It's

Cosmost likes full sun. It's daylight sensitive, so if it's not getting enough sun, it may be failing in health. Are you deadheading? Removing spent blooms encourages the plant to put its energy into new flowers, not seeds in old ones.

I'm getting ready to plant

I'm getting ready to plant beginners that are currently in Dixie cups. I'm in eastern Nebraska. The area I will be planting in is mostly shade. Will they grow right or do they need mostly sun.

I live in Maryland. Last year

I live in Maryland. Last year I put half my seeds in full sun and half in mostly shade. I got tremendous results from the full sun. The mostly shade grew a lot slower, were much smaller, and had a lot fewer flowers. - Good luck!

is it advisable to cut the

is it advisable to cut the cosmos in half when still growing to promote stronger thicker stems

We would not recommend it.

We would not recommend it. Cosmos do not ask for much: they thrive in fairly poor soil, just make sure the soil drains well (and the plants are not in puddles). Too-rich soil may result in thin-stemmed, weak plants; cutting them will only hasten their demise. Stake tall stems again heavy rain or wind, when forecast. Or plant the flowers closer together than seed packages or plant labels advise so they can support each other. Pinching off flowers encourages blooms. Pinching stem tips can reduce height and encourage branches to grow but it is not necessary.

I want to plant cosmos for

I want to plant cosmos for the first time this year. The bed is all prepared: weeds are pulled, soil was tilled and raked flat, and it's finally stopped raining enough that my flower bed isn't sticky clay-mud.

But it's pretty late in the season - we had our last frost in early May and it's been a cold, wet, rainy mucky month, so I won't have a chance to get these planted until June first. Will they still germinate, grow, and flower in that time?

You should be able to get

You should be able to get some flowers before the end of season if you plant the seeds now. It all depends on when you get your first frost in the fall. Cosmos are very sensitive to the cold.

Yes but it will take about

Yes but it will take about 7-8 wks...I live In zone 4a-b and seed when there's still frost end of April early May as cold helps cosmos to germinate... My plants are only 4 inches and I only seeded a few weeks ago this year but as soon as it gets and stays hot hot they will have a huge growth spurt! last year I seeded eight weeks before the last frost indoors and it was a waste of time I could've sown straight into the ground and the plants end up the exact same size ! Make sure they are planted in almost sand not a rich organic soil - they do much better this way as they are native to Mexico...and plant very thick -4 to 6 inches apart as this supports the tall stems in a fluffy green hedge ....mine were almost 4 feet high last summer and I do it this way every yr. ....think of it as a burst of colour for end of July when everything else is on the wane or looking faded -they will last right up until it freezes and prolifically self seed for the following year. I also let seeds mature on the biggest and best flowers and collect and keep in a ziplock in freezer to supplement all the volunteers in spring. Otherwise they are spindly and fall over. Ignore spacing guides and plant much closer together and u won't be sorry! Hope this helps...I learned the best way how from Mr. Lim who owns a variety store with a 3 foot deep 20 foot long hedge of cosmos every year -they look so striking and fantastic!! Even if u only have 2sq.' U can fit in 18 or so plants!

It all depends on when you

It all depends on when you get your first frost. I planted cosmos, cornflower, zenias and forget-me-nots last year in mid-July, zone 5b. I had flowers in 6 weeks or so up until the first frost, November I think. I just sow the seeds on some loose soil, cover them with mulch then keep them watered.

Hello, My cosmos have

Hello, My cosmos have flowered and some of the flower are dying off. At what point do I collect seeds? I'm not sure what the seeds look like? How will I store them? Sorry I'm very new to all this and just love this flower and would love to plant and nurture again next year. Thank you

Hi Jacqueline, If you just

Hi Jacqueline,
If you just cut off the spent flowers now you'll get many more blooms to enjoy during the summer months. You can cut some of the stems with flowers to put in a vase and this will also encourage the plant to produce more stems and blooms.Toward the end of summer you can leave the flowers on the plant to go to seed. Just leave them on the stems and after a couple of weeks you'll see the spiky seeds where the flowers were. You can store the seeds in an envelope or container in a dry dark place.

...they are in the center of

...they are in the center of the flower in a crescent moon shape -as the flower dries they start to separate and you can see them quite clearly about an eighth of an inch long ....let them dry right on the flower but make sure you get them as they start to open up and separate or They'll self seed the petals will have died back at that point... I actually counted over 4000 seeds from a hedge only a foot deep and about 10 feet long ...I store in the freezer until about the end of April here in zone 4a. Takes about 11/2-2 mos. from sowing to flowers next yr...

Hi iwould be happy to answer

Hi iwould be happy to answer this question for you after your cosmos finish flowering and fall of the head will be green the seeds will turn brown or black that will tell you that they have ripen on the flower head grab the whole flower head to pull off the seeds you can store in a paper bag next yeat to dry brad hopes this help

I used my cosmo seeds from

I used my cosmo seeds from last year which I planted about 6 weeks ago (approximately), & they were all around 1" tall now. Unfortunately my landlord decided to spray for weeds & sprayed my flowers, since it is already the end of April, is it too late to plant them from seeds again in order to enjoy them through the summer or should I have them replace them with flowers & do you think it is safe to plant again since they sprayed weed killer on the soil? (I did the same with my zinnias)

I saved seeds from my cosmos

I saved seeds from my cosmos last fall--also seeds from calendula, zinnia, verbena bonariensis, and one called Kiss Me
Over the Garden Gate. I kept seeds inside all winter. Do I have to treat any of them to a freeze before planting them this spring?

It is not necessary to freeze

It is not necessary to freeze your seeds before planting them.

Let the cosmos flowers bloom

Let the cosmos flowers bloom all along the roads and railways!

I've had Cosmos in the yard

I've had Cosmos in the yard for a few years. I allow them to self seed but last year not many came back. I have more seeds but am not sure of the best time to sow. I live in zone 9/10 in Southern California where we don't have frosts. When should I sow?

Hi all, am new to gardening

Hi all, am new to gardening but I am keen on having my own flower garden. I have bought a pack of cosmos seeds and plan to grow them in pots. How deep should each pot be? How many seedlings can I plant in one pot? Am planning to germinate the seeds in a seed tray.

Please advise.

You can start the seeds in

You can start the seeds in the pots directly. Sow them about 1 1/2 inches apart. The pots don't need to be too deep. Put the pots in a spot where they will get about 8 to 10 hours of sunlight a day.

I've grown cosmos for many

I've grown cosmos for many years. It is one of my favorite flowers. Sometimes I have a white slimy substance on the plants. What is this and will it hurt the plant?

It sounds like it might be

It sounds like it might be white smut. Improve air circulation around the plants as well as light. You should remove and destroy plants with any signs of white smut and then treat with a fungicide (ask at your local nursery for fungicide suggestions).

Hello Bettye, I've been

Hello Bettye, I've been growing Cosmos my whole life. The white slimy substance is a bugs cacoon. If u look at it very close u can see the bug inside of the slime. Take ur hose and a rag and get it off. The bug will eat ur plant and infect the others. Hope that helped u.

Love the look of this plant.

Love the look of this plant. I have bought some seeds but it is already the end of AUG and I am wondering when is the best time of year to plant these seeds...? How do I store the seeds until planting time?
I am a novice at this

What climate zone do you live

What climate zone do you live in? It is probably too late to plant seeds unless you live in Zones 10 or 11. Otherwise, plant seeds in Spring after last frost.

Question about color genetics

Question about color genetics on Cosmos. Do they breed true to color or cross pollinate with other colors? Every year I try to increase the amount of white cosmos, but it seems no matter how careful I am in harvesting and separating out my white seed, some purples come out in the beds of what should all be white seed. And what about the more exotic colors/types, like the physco white, and coral bells, etc? Will those breed true from the seed I save this year?

There are a lot of species of

There are a lot of species of Cosmos. Many of them cross-pollinate to create hybrids. You will have a better chance to get true colors if you start out with heirloom or open pollinated seeds.

I have been growing cosmos

I have been growing cosmos for years, and never had a single problem with them, until this year. I always like to collect the seeds and plant them the following year, but this year I found a package of candy stripe cosmos and had to have it. They are growing fine in a planter box, and they flower, but as soon as they flower, the stalk right under the flower starts to die, and then I am left with 2 or 3 inch dead section, with a flower hanging off the end. But the rest of the plant doesn't die, and appears healthy. I am wondering if the package I bought has a disease maybe? Or if it's the soil. I tried a new dirt this year, maybe it's too rich? I Can't recall the name, but it's the kind that expands three times it's size and has 6 months fertilizer in it. The others in the yard, and doing fine. Those are last years seeds. Any help would be great. I do have a picture I can email if anyone wants to see.

It might be stem caker or it

It might be stem caker or it could be a fungi in the soil or it could be something else. The source of the problem is not always in the place that it manifests/appears. More water is not the answer. Here is an (admittedly detailed) page on a wide variety of plant problems that may give you insight.

Cosmos are not fussy feeders.

Cosmos are not fussy feeders. They need very little fertiliser and can tolerate dry conditions. See the web page on Cosmos hints on growth.

I live in a tropical country

I live in a tropical country so it's sunny all throughout. I just bought cosmos that's about 2months old. About a few weeks or so after, the leaves started drying out until one stalk just died on me. Flowers don't bloom completely and some buds just turned brown. I water them everyday, even put the crystal fertilizer once but it's continuing to die on me.

These plants can thrive in

These plants can thrive in fairly dry soil. Perhaps you are overwatering them. Also they do not like rich soil so leave out the fertilizer.

Hi Cosmo world! I live in CT

Hi Cosmo world!

I live in CT and have have head started cosmo seeds indoors in April. I transplanted them outdoors when they were about 3-4 inches tall. My cosmos have not grown too much taller, they are about 6 inches tall and are already flowering! Are they flowering prematurely? Their flowers are only a half an inch wide and I have only had 1-2 bloom. I dead head them in hopes to get bigger and more blooms! What can I do different? Is it a mistake to have them in the same bed as Zinnias?

Cosmos and zinnias are fine

Cosmos and zinnias are fine together. I've raised them that way for years. Zinnias bloom first, and then about the time fungus starts to take them, the cosmos take over, soaring above the zinnias making a very nice display.

I planted cosmos for the

I planted cosmos for the first time about 8 weeks ago. Currently there are lots of stems, but no flowers in sight. To my dismay I am reading here that I have obviously been too "nice" to them! I water them almost daily and fertilize every few weeks. My question is that if I lay off the love, with they start to flower? I am such a newbie gardener, I'm hoping they aren't a total wash this season!

Cosmos usually grow tall

Cosmos usually grow tall stems first before they put out any flowers. Cut back on the fertilizer and only water if the soil is very dry.

I think you are right. They

I think you are right. They can thrive in fairly dry soil and do not like rich soil. Lay off the love yes.

Every year I have been

Every year I have been planting Cosmos in a longish narrow strip outside my back veranda (I am in a rented suite) and they have come up beautifully. I always grow from seed (3 packages) and by June to July I have a Cosmos "forest". This year I planted as usual in March and just checked the bed. There are only about 12 Cosmos that have come up and we have had a lovely warm spring so far (I live just outside Vancouver in Surrey, B.C.). What I thought were the usual number (often 30 or more) I can see now is grass weeds! The only thing I did differently this year is not adding a couple of bags of fresh soil over the old soil. I just raked some compost in the bed and took out old roots and rocks. Is this what I've done wrong? (I'll go and buy some more seed but it's a bit late to start them now!) Thanks for any suggestions.

Hi Louisa, In past years you

Hi Louisa,
In past years you have smothered the weeds with fresh soil. This year the cosmos seed had to compete with the weeds. Pull out the weeds, add a bit of fresh soil and plant some more seed. There is still time for the flowers to germinate and bloom this summer.

I have grown cosmos from seed

I have grown cosmos from seed for the second year, but the plants are quite leggy again. I note the comments about no pampering and treat them mean, but should I pinch out the tip of the seedlings to give a more bushy plant?

Not too late at all to start

Not too late at all to start by June 1st -u will have flowers end of July and longer than Toronto cuz we get frost quite early....

I have some cosmos in my

I have some cosmos in my garden and I have a black & whit speckled beetle that is sucking on the flowers so the flowers die. What can I use to keep the beetles away?

Use neem oil or spray with

Use neem oil or spray with insecticidal soap which you can find at any garden center (or make yourself).

i have cosmos plant something

i have cosmos plant something around three feet.i shock my plant height three feet and above. i give watered regular in a day at evening and i am very happy today morning on the roof plant have white colour flower also some defferent honey bees on this flower.some hour after i see a ladybug.

We live in New Zealand and

We live in New Zealand and must be doing something wrong. My wife is in charge of the cosmos, which she grows from seedlings purchased locally, although there are also some self-sown plants here and there as well.
I planted the seedlings about a foot to 18 inches apart; my wife scattered all-purpose fertiliser pellets among them. The cosmos formed dense bushes about 6 feet tall with dozens of flowers. They are watered daily at ground level and are thriving. According to the postings here, we are doing it all wrong, but we've actually had passers-by call in to express their admiration of the plants!
We've been growing them for about ten years now and have always been very successful with them - but will now bear in mind that we should cut back on the watering if they do start to look sickly.
They are not dead-headed - the plants are grown specifically to attract goldfinches who love the seeds.
There are not many butterflies in this country, but the few we do have like the flowers as well.

Yes, me too. I live in New

Yes, me too. I live in New Zealand and my cosmos have reached great heights with a few with flowers reaching nearly 7 feet tall and others around 6 feet an 4 feet wide. Like you, I don't deadhead, and as I'm an amateur gardener who knew nothing about cosmos, was delighted when babies started shooting up, so am hoping to grow some more large ones. Did any of your second-generation not grow tall? I'm thinking it was because I left them to grow naturally and did not give them the TLC I gave the others, so am doing that with the new ones coming on. Now I have so many I don't know what to do with them! However, am loathe to get rid of them as I love them so much. Do they still grow during winter? What happens to those who are still large?

Good to hear of your

Good to hear of your experience with cosmos, Raewyn. We too have little chaps sprouting up all over the place - and they don't seem to get any higher than about 6 inches.
The sad part is that they all die back as soon as there's a frost and in no time at all, there's just a dried up white skeleton. The babies come to nothing despite their healthy beginnings.
There's always next year and a plentiful supply of seedlings at the plant shop - and we always seem to end up with the taller varieties!

I'm in the UK and bought a

I'm in the UK and bought a packet of wild flower seeds. The only thing that relly stood out were the wonderful tall light purple cosmos. I am looking forward to next year.Yes they only flower until the frost so maybe they keep going in hotter countries?

The cemetery where my

The cemetery where my father-in-law is buried gave us some wildflower seeds they said were perennials to plant as a memorial. They turned out to be cosmos which grew into a very tall (over 6' & still growing), spidery bush with long arms and gorgeous hot pink flowers. I'd never seen anything like it and absolutely love it! I'm very disappointed to read here that it's an annual! Any chance it could be a perennial?

Cosmos are an annual.  There

Cosmos are an annual.  There are also perennial species in cultivation, but it wouldn't be grown from seed. Cosmos comes from the Greek word kosmos, meaning “beautiful" and is a member of the aster family. Though it's an annual, cosmos has been known to self-seed and bloom again. If you do not deadheaded (remove the spent flowers), it will self-sow in warm regions.

I thought I remembered

I thought I remembered another name for the Cosmos flower. I seem to remember it as ' ? in the mist' Have you a clue?

Could you be thinking of

Could you be thinking of 'love in a mist'? It also has fine fern-like foliage but not actually a cosmos - a nigella. Although there are white and pink varieties (I believe) the traditional love in a mist are more commonly blue.

There may be a very good

There may be a very good chance the Cosmos can be a perennial. I live in a colder climate and get Cosmos back every year. Just let the flowers go to seed and drop in the fall.

I meant that let the seed

I meant that let the seed heads drop in the fall!

Doesn't that mean they are

Doesn't that mean they are annual if it's the seed that keeps them going. Perennial means they grow again from the root doesn't it?

Most of the Cosmos varieties

  • Most of the Cosmos varieties are annuals and are started from seed in spring. There are a few perennial varieties of cosmos that have rhizomes and can be propagated by division.

First of all, I live in

First of all, I live in Calgary, Canada where the growing season is short, but it gets to between 25 and 30 degrees Celsius in the summer I grew 60 cosmos plants this year from seed, as it takes too long for them to come up before the frost hits. I had wonderful success with them, some getting over 5 feet tall and full of blossoms. Some were planted directly in the beds and others in pots. Some had full sun and others had partial sun. Everything grew beautifully. I put compost in the soil at initial planting and then only fertilized once with a fertilizer for flower plants. Everything was beautiful until the city got an aphid infestation. I sprayed every week with Safer's Insecticidal soap and that helped a lot. After a while I got tired of spraying, so did a lot of clipping off of branches that had aphids. This an spraying seemed to bring the aphids under control. I water fairly well every day, before they droop, and always in the morning or before supper, and from the top of the plant. I have not had any problem at all with mildew (which I do get on other plants). Mildew comes when the water on the plant's leaves don't get a chance to evaporate, and they stay damp, especially if the temperature dips at night. I will be very sorry to see the end of the season arrive as my yard is full of these beautiful, unkempt looking flowers. When branches have broken I have taken them inside and within a few days any buds have opened and they continue to blossom beautifully.

how long does it take for the

how long does it take for the cosmos to grow from a seed to a flower?

I would say six weeks but

I would say six weeks but that is in the UK. Not sure about other climates.

Aphids can be cleaned up

Aphids can be cleaned up really quickly with ladybugs. They are a natural predator for aphids. They can clean up an infested tree, rose bush, or garden plant in just a few days. You order them, then keep in frig until needed. The challenge is keeping them in your yard. They will leave, eventually, but their offspring, in various stages of development, continue to feed on aphids.

we had 3 cosmo plants that

we had 3 cosmo plants that got big enough to do something this year. it was our first time with them and im sure we watered them too much. anyway one flowered several times and died but the remaining two are now like 3 feet tall, very bushy, but not a flower in sight. not even any little buds anywhere on the cosmo trees as i now call them. whats going on with them?

Hi, Clair, Cosmos hate TLC.

Hi, Clair, Cosmos hate TLC. Treat them poorly! That means almost no watering (once a week) and NO fertilizer or compost and not much care.
Blooming is reduced if overwatered or managed. Soil that is too nutrient rich produces plants that are weak-stemmed and have sparse to no flowers.
Do make sure your soil drains well but, otherwise, soil with average to poor fertility is fine. Cosmos PREFER pool soil so not much soil prep is needed. Plant in a drier area of the garden; they are from Mexico so think of their native climate.

I live in SE Wisconsin and I

I live in SE Wisconsin and I have four orange cosmos plants in a big pot that are growing very tall and leggy. There are tons of seed pods everywhere, but fewer and fewer flowers. I thought cutting them back a bit would help, but I don't think it did. Some of the stems I cut back just turned brown and died, while others sprouted new flowers down below. I guess my question is: what is the best way to prune these guys? Is there a rule of thumb (i.e. with roses, you always look for three leaves) or should I just remove the dead flowers and let nature take its course?

(Amended answer) I think you

(Amended answer) I think you need to wait until the flower dies and the seed head starts forming on the plant before bringing it indoors. If you cut the flowers when blooming and bring them inside they will not form seed heads. Tying a paper bag over the seed heads in the garden is a good idea.
It sounds as if your cosmos grew quite tall; next year, try pinching them back when they're young and they will stay more compact and bushy.

Just a quick comment to

Just a quick comment to answer yours Almanac. You do not have to cut off spent flowers to get further blooms. I started off doing that, but quickly discovered I kept getting many, many new flowers, even more than before, by not cutting them off, as sometimes a new bloom will come off the same stork, so you could actually get less in the long run. Another secret that some may not know is milk and water. One part milk, two parts water - its amazing and gets rid of black spot, plus can make a sick or very dead looking plant or vine come back to life. I had a vine that was completely barren, devoid of any life. After months of putting milk and water on it (I thought I had nothing to lose), I now have a flourishing beautiful vine! It was quite miraculous. Great website by the way!

Thank you, Raewyn. We have

Thank you, Raewyn. We have amended our comment—and we really appreciate our tips. Thank you for sharing your experience!

Please would you help me with

Please would you help me with a question about harvesting cosmos seeds. In past years I waited for the seeds to dry completely on the plant and split open before harvesting them. This year however, birds and chipmunks have been eating about 95% of the seeds before I can get to them, and I do check them daily. If I pick the seeds with the long stems before they dry and then dry them indoors inside a paper bag, will they be viable for planting next year? Thank you very much,

We suggest that you pick the

We suggest that you pick the flowers. Then dry the flowers completely in a place where they will not move—or if moved, will drop their seeds in a way/place (on paper?) that they are easily retrievable. When the flowers are dry, remove the seeds from the heads, and place them in a paper bag in a cool, dry location.

I was wondering would you be

I was wondering would you be able to wrap a paper bag around the flower head and simply hang it . The bag would catch all the seeds and it could still breathe through the paper. Its what was suggested to me for my sunflower heads. Worked well for me.

Thank you for your

Thank you for your suggestion, Troy, of wrapping the flower heads in paper bags and let them dry. It would be easy and practical with sunflowers but not with cosmos, as there are far too many blooms and the paper bags get all wet and torn when it rains. I simply cut off the mature seed pods after the flower petals fell and dried them on a flat tray until the seeds turn black. Then I took them all indoors and store them in a cool place inside brown paper bags. I look forward to hearing more ideas from you and other enthusiastic gardeners. It's great fun growing things. Thank you again,

I would think if you picked

I would think if you picked them when still just flowers the seed would never mature? I pick my seed any time from when it "stars" completely open or as soon as he seed in the still closed form has started to turn black. You do take the risk of loosing some seed if you let them open all the way as they shatter easily. I dry seeds completely on screens and then store in glass jars.

I buy several packs. Some

I buy several packs. Some plants grow to be very bushy but few, if any blooms. Some plants maybe grow to 15", scraggy growth, but blooms. Ohter plants grow to be "normal" This is the second year this has happened. Any ideas why the difference in the same bed. Thanks

Hardly anyone has a bad word

Hardly anyone has a bad word to say about cosmos; most sources indicate that they just keep on coming, so we will hazard a guess at your problem: As lovely as they are, Cosmos are sometimes described as a weeds because it heavily self-seeds. Well, sometimes even weeds fail to thrive. Speaking of weeds, control of them during cosmos germination time is critical to the flower's survival.
Cosmos seed germination is reduced when temps are above 80°F or below 65°F, so maybe many of the seeds did not make it through the winter. Or it was too hot during optimal germination time.
Another thought: Cosmos needs to fertilizer; in fact, it prefers ordinary to poor soil. In fact, too-rich soil can result in weak stems. Save the good sol and fertilizer for other plants!
Cosmost like full sun—at least 8 hours per day of intense light.
We hope this helps.

My cosmos are slowly turning

My cosmos are slowly turning brown & seem to be dying. I have a lot of brown stems & they aren't blooming very well anymore. I only water them when the soil is dry, I also deadhead them about once a week. Any tips.

If the entire plant, flower,

If the entire plant, flower, or leave is turning brown, then it's possible that your plant has a fungus called gray mold. You could bring a sample to a local nursery or your cooperative extension for a diagnosis. If gray mold is present, you need to remove infected plant parts and dispose of them. This fungus happens when plants don't dry out well--either due to wet weather or overhead watering or crowded conditions. Water at soil level and avoid getting water on leaves and petals. Allow more space between plants.

We have cosmos & moss rose

We have cosmos & moss rose planter in large cedar boxes on our deck, full sun. They are beautiful but are slowing dying off. Once the bud is spent I cut then down but most ( not all) do the stalks turn "woody" and die. Am I doing something wrong and is there anything I can do to prevent this ? We are also fertilizing.

Our first thought is that

Our first thought is that they are not companionable—that they have different needs—and on further research it appears to be the case. According to one source, moss roses bloom once and do best in afternoon shade and in a bed that is well mulched, ensuring that the rose is not water stressed. Cosmos likes full sun but tolerates some shade and does not do well in rich soil.

I just discovered Cosmos

I just discovered Cosmos double click cranberries and bought the seeds. CAn I plant them in south Louisiana now. It is the last week of July. I also have cupids dart, blanket flowr, sibrian wallflower, lavender and purple coneflower seeds. Should I just keep all of these until spring?

It is a bit late in the

It is a bit late in the season to start flowers from seed. If you grow them outdoors you need to be aware of your first possible frost date this fall (beginning of Nov. in your area). The double click cranberries take 10-21 days to germinate. If you save the seeds for next year you'll be able to enjoy these beautiful cosmos all summer long.

I live in AZ. I planted

I live in AZ. I planted cosmos with new seeds early in March.
They are about 3 ft. or more tall now with attractive foliage,
but still no sign of a flower. (The seeds that I planted in pots came up beautifully, but burnt up in May. What am I doing wrong?

Cosmos take 7 weeks to bloom.

Cosmos take 7 weeks to bloom. Are there buds yet? The usual reason for lack of blooms is fertilizer. Cosmos do not really like fertilizer. They thrive in weak soil! Cut back on fertilizing. Never coddle cosmos. Tough love!

The article was saying you

The article was saying you can harvest seeds. When should I cut the flower head off to receive seeds and how to handle them to produce seeds sun dry or sit them out only? thank you so much Blain W.
P.S. My beautiful cosmos are 5ft and I have short ones due to Deer eating tops off when young, also took since about 2.5-3 months for blooming at full growth. Worth the wait all the way, Thank You God for the beauty you created for us.

I have the orange cosmos

I have the orange cosmos flowers. My friend who gave me my first cosmos plant seeds said if they flower, they will come back the next year. I am about 5'4" and I have some that are taller than me. For seeds, I wait until they are dry and prickly looking, then just pick the ends (seeds) off and put them in a Ziploc bag to have for the next year, although mine came up by themselves this year, and they do spread rapidly. They are very pretty flowers, I agree.

I have gotten new seeds and

I have gotten new seeds and put them into a pot. They grow fine, but then after a week they tend to shrivel up. I am not sure exactly If I am over-watering or if they are not getting enough sun. I've asked a few people and they said since they are about two weeks old, I am giving them TOO much sun. I let them sit on my step outside for 8 hours a day, is it too much. I understand how to take care of them.. I am just confused. What do you suggest?

Cosmos can't get too much

Cosmos can't get too much sun. They are sun-loving annuals and enjoy 8 to 10 hours of direct sunlight. The usual problem is overwatering. Water them very sparingly. Basically, cosmos thrive on neglect! Only water when the foliage starts to wilt. They are drought-tolerant.

pinching out young Plants (COSMOS)


For cosmos, pinching promotes

For cosmos, pinching promotes more blooming. Deadhead spent flowers. When they are getting older with lots of seed pods, cut the plants back to 12 - 18 inches high.


How much water should i give my Cosmos everyday ?

Water only when the soil is

Water only when the soil is dry and when the plants look like they need some water. Cosmos plants don't like to be wet.

seedlings need help

I have two small greenhouse kits with white cosmos I planted them a week ago and now have a dozen sprouts around 2-3 in. tall with two leefs a piece they look good but I'm finding mold is starting to grow in the moist soil should I move them to pots already or maybe leave the lids off I'm at a loss any help would be Much appreciated~arkansas

Remove the lids and let the

Remove the lids and let the soil dry a bit. Air circulation will also help. The mold is not going to hurt your seedlings and may disappear with drier conditions.

Can aphids be in the city or greenhouse?

I've just heard that aphids will kill my cosmos and I am scared of bugs and I live in a city with lots of sun and I want to plant cosmos but I don't know where to plant it without it having aphids. I can plant it indoors(I have a sunny window),outside, or in my green house please help!

First: if you're growing

First: if you're growing plants, you are going to encounter bugs. Before you even spot aphids, spray your plants every couple days with a few stiff sprays of water. If/once you spot aphids, just spray with insecticidal soap (soapy water) on all sides of the leaves. This should work with minor infestations before it gets out of hand. You can always resort to chemicals, but staying on top of the issue is best for you. Finally, if you notice aphids, release tons of ladybugs, our sweet beneficial insect which lives on...eating aphids! Now, ladybugs are "bugs," too. :-) In a greenhouse, they are aphid-eating machines.


Thanks that help me a lot I'm just scared of most bugs that don't seem friendly and also do all cosmos get aphids?cause if some don't that'll be much easier and are they harmful to humans?

Hello, I planted a beautiful

Hello, I planted a beautiful Cosmos in my garden last year, it had flowers all the summer, it died off in the winter, I didn't do anything with it, will it come up again this year, or is it totally dead?

The most common species of

The most common species of cosmos are annuals. The seeds need to be replanted each spring. This showy flower is easy to grow if you have full sun. Enjoy!

Do cosmos come back in the

Do cosmos come back in the same color? Was thrilled to have great success with orange cosmos directly sown from seed this year. I have tons of seeds to save for next year. Will they come back orange, or another more dominant color? Thanks!

It should come back in late

It should come back in late spring, as long as you allowed the flower to reseed itself. It may not come back in the exact same spot that you originally planted it.

Yes, they will spread a lot

Yes, they will spread a lot each year, after the first year they flower and re-seed.

Lanky Seedlings

Hi from UK. I've read your comments and now know to 'treat them tough' my question is, my seedlings after sowing in one week indoors in trays are now approximate 2" with initially leaves. I'm concerned they are bolting and are weak plants. Although theses leaves are not the true leaves can/should I repot then leaving only 1/4 showing and hope they will not be weak or will the stem rot? I intend to transplant these early seedlings to small pots in a HEATED greenhouse, it's 1'C here today. Should I start again in the heated greenhouse full light and trash these indoor seedlings?

If the seedlings are too

If the seedlings are too crowded repot them in small individual pots and then transfer them to your greenhouse. The seedlings need air circulation and not too much water. Water from the bottom if possible (make sure your pots have holes in the bottom).
Good luck!


Thanks can I repot tem quite deep or will they rot?

Cover with soil about 1/4

Cover with soil about 1/4 inch. Follow our instructions on this page for seeding.


Thanks :)

Az. Heat in summer

You say Cosmos loves hot weather and sun. I live in Az where summer temps can get from 110 to 120 at times. Is this kind of heat ok for me to put in full sun?
Thank you

Yes, cosmos are great flowers

Yes, cosmos are great flowers that still bloom in AZ in the summer heat and they attract the butterflies, too. Direct seed outdoors in March.

when were the cosmos first

when were the cosmos first discovered

Cosmos will bloom until the autumn harvest.

I'm looking forward to a healthy house plant to have forever. I looking forward to profuse growth of color and leaves

Is artificial light ok?

I'm planning to grow 4 cosmos (1 in each pot) for a science experiment. It's going to have to be grown indoors, and since it's wintertime here, they won't be getting much sunlight. Would artificial light be ok for them? thanks for your help! :)

Use a growing light and make

Use a growing light and make sure the pots are in a warm area. Good luck with the experiment!

pot size

I forgot to ask along with the other message, how tall and wide should each pot be? and thanks!

If you are growing one plant

If you are growing one plant in each pot they don't need to be too big. A 6-inch pot will do great. Good luck!

Week seedlings

When I purchase Cosmos from the burserty they are usually 4" tall and have strong stems. When I grow them from seeds in Jiffy Pots they grow fast and long with weak flexible stems which bruise and die when transplanted. What am I doing wrong?

weak seedlings

'burserty' sorry meant nursery

Cosmos need a lot of sunlight

Cosmos need a lot of sunlight to grow well. You may need more light and warmth for your seedlings to become stronger. Use a growing light placed about 6 inches above the soil if the seedlings don't receive enough sunlight.

Great article, thanks for

Great article, thanks for posting!

I have very limited space, so I have to grow everything in containers. How many plants per container would you advise? And what size of container? Thanks!

You can use small to large

You can use small to large containers. Plant 3 to 4 flowers in a small container and up to 8-10 in a bigger container. Try different varieties as cosmos come in different sizes. Make sure to remove spent flowers for a bushier growth.

Winter ground care

After the first hard freeze, do I mow down the cosmos or do I pull them out by the roots?

Cosmos are annuals, so

Cosmos are annuals, so digging them up will be your best solution.

Thank you for your reply. My

Thank you for your reply. My cosmos have been returning every year for years so they must be reseeding themselves - is digging them up still the best solution? I have dug them up every year, but guess I am getting lazy and looking for an easier way if there is one.

2 1/2 feet tall cosmos-healthy, NO BLOOM

I started from seed indoors. Planted outside 8 weeks ago. Cosmos plants are thriving. But no buds at all. Non-amended soil. 6 hours sun. Spotty watering. HELP!!

Not sure what variety of

Not sure what variety of cosmos you have. Give them another week or so. The plants are still pretty short. With less daylight the plants don't grow as fast as in the summer.

Cosmos blooming dry and dead

i grew Cosmos from seed and they are just THRIVING! I have dozens of healthy beautiful neon orange flowers, but now some of the flowers are blooming already dry and deformed that I have to deadhead them right when they open. The leaves on one plant are turning brown from the inside out. I didn't realize I had been watering them too much(once daily, keeping the soil moist, I'll cut back) I have also been misting which I will stop doing(but it was working great). I haven't used any fertilizer, just the miracle grow I first put them in. They get plenty of blazing hot Utah dry sun. I'm in the middle of the city in a condo complex so I really don't see insects as the culprit. Am I just over watering?


Yes, stop watering and misting! The general rules with cosmos are: 1) do not overwater cosmos; water so sparingly that you wait until the leaves are wilting before you water again, 2) do not overcrowd cosmos which need lots of air circulation (and you sound as if you have dozens in a small space?), 3) withhold fertilizer as they love to struggle in poor soil, 4) look for mildew-resistant varieties, 5) hope for low air humidity, 6) use well-drained soil, and 7) do not water from overhead; water at soil level. All of above keeps cosmos from getting a plant disease such as powdery mildew or a wilt. You may wish to take a sample to your local county cooperative extension or garden center to get a diagnosis.

cosmo update

I've started to withhold watering until the very last minute. I have done no fertilizing. The first blooms are still going strong but new blooms are still struggling and I am constantly deadheading. I believe the crowding is the issue. There are about 4 plants in each grouping about 12 inches apart from each other so it is pretty crowded in there. I will completely seperate them if needed

my cosmos are dying...

My Beautiful Cosmo Plant is dying. I put in my flower bed with fertilizer it was growing pretty nice unti now its really dead the steams are turning brown and their dying
what can I do?

Well I just read in my garden

Well I just read in my garden magazine that they do not like fertilizer. In fact it says they grow best in crummy soil as long as it's well drained!

That is correct! For more

That is correct! For more bloom, hold back water and any fertilizer. Give them all-out, blazing sunlight and no shade. They like to struggle and are very drought-tolerant. Do not baby them at all. They want no lovin'.

Be sure that you are not

Be sure that you are not overwatering. Cosmos prefer to dry out in between waterings.

Also, check to make sure that they aren't crowded and that there are not aphids destroying your flower.

Sadly I think it may be crowded...

I let my little girl plant the seeds, while i was doing other things in the garden and told her to only put 2 in each hole and she put 4 in each. The are four big healthy plants coming out on each section. The majority of the flowers are just beautiful but some are coming out dry and dead now. I'm going to cut back on watering and see if it helps. Thanks

Leaf curling

My cosmos seem to be fairly healthy but a few plants have leaves that have rolled up. What's wrong?

Check underneath the leave

Check underneath the leaves for bugs; if you see aphids, spray them with insecticidal soap. Also be careful not to overwater cosmos. Water sparingly and at the soil line (not from overhead); they can take the sun and heat. Let them dry out completely between waterings and make sure they have enough air circulation and aren't crowded.

cosmos wont flower

our cosmos are growing nice and tall. We are fertilizing them but they haven't bloomed yet. Keep the soil moist and gettting good sun. Any suggestions?

You may be babying the

You may be babying the cosmos. They thrive on neglect--heat, lack of water, poor soil, etc. Don't feed them a high-nitrogen food or they won't bloom. Withhold water to the extent that you can. Keep giving them sunlight.


when I withhold water they get droopy and seem to shrivel pretty bad. Is that ok? How much sunlight do they need?


Cosmos like full sun (at least 6 hours of sun daily). If the plants shrivel give them some water.

Cosmos won't flower

I planted a combo of seeds purchased from a wildflower farm in Texas in March. The seeds came up but it appears I have two different types of Cosmos. The smaller / shorter plants ~ 2 feet tall are blooming. I also have another version that have very thick stalkes ~ 1" dbh and approximately 4' tall. None of the larger plants have bloomed. They receive full sun and the plants look beautiful but no flowers. ?? Help ??

Cosmos are great for Texas

Cosmos are great for Texas gardens. For more bloom, hold back water and any fertilizer. Give them all-out, blazing sunlight and no shade. They like to struggle and are very drought-tolerant.

Do not fertilize cosmos. They

Do not fertilize cosmos. They need "tough-love" -- very little if any fertility. And water sparingly. They want blazing sun and like it HOT and DRY!

Indoor Cosmos

I recently purchased a small Cosmos plant that had a small bud on it, however, I live in a flat so I can't put it outside. What should I do?

Cosmos make great container

Cosmos make great container plants so it should be all set as an indoor plant.

However, make sure the plant receives lots of indoor light!

Thank you for your interest in the Old Farmer's Almanac and our Web site.


I am wondering if they are candy for the deer. Hopefully they are deer resistant. Please someone. thank you

We like to say that there's

We like to say that there's no such thing as a truly deer-resistant plant, however, deer will usually pick other flowers over cosmos due to the stiff stems and less appetizing leaves. Cosmos is NOT candy. See our top deer-resistant plants here:

How are Cosmos Supposed to Grow?

I started my cosmos from seed in March, which now I'm thinking was a little too early for these guys. When I went to plant them in pots they had long lanky stems. As of right now they kind of look like ground cover because they can't stand up. Should they lie of the ground like that or should I prop them up? Thanks!

The cosmos stems are lanky

The cosmos stems are lanky because they didn't get enough light as seedlings. They are warm-weather annuals and you need lots of indoor light. At this point, can you direct seed? I'm not sure where you live but perhaps the seedlings will germinate at the right time and you'll have sturdy stems. Seed in FULL sun!

You forgot the Praying Mantis.

I am striving for a self efficient garden and have planted seeds all around my yard and fence to bring in the Praying Mantis. I'm a bit impatient too as bugs have taken over my plants and yard for two years with spraying being non effective so I bought some egg sacks too.

Praying Mantis travel at night too so leaving lights on outside for a bit helps to bring them in.

Cosmo blooms drying out

I am dead heading the dead and dying blooms. PROBLEM: The plants are blooming profusely, however, the blooms are drying out before they open even half way. I have them on a misting system and planted them with Kellogs soil amend. The soil was mostly decomposed granite and juniper tree and oak leaves. Why are the blooms drying out prematurely. They are getting filtered sun all day. Any suggestions?

A couple possibilities come

A couple possibilities come to mind - that perhaps they don't like the misting (or that the blooms don't tolerate it well, anyways), or that maybe they're not getting quite as much sun as they'd prefer (depending on how filtered the light is)?

I'm growing cosmos for the first time this year myself, so I'm afraid that I speak not from experience but just based on what I've read and heard.

Not sure where you're located or exactly what environment you have the plants in, but one other thought is to wonder if temperatures might have something to do with it - if it got a bit too cold, I could see that affecting any existing blooms.

Cosmo transplanting and germinating

I live in MD where Fall is almost here. my bushes are in 12 inch pots and are at least 3 feet high. Ideally I would like to remove them from the pot, split them I think and bury them along the side of my house. How do I do this first of all and will they germinate so that new cosmos grow and spread each year? How deep do I bury them and do I cut them down?. Last, do I cut them down and will they survive a cold winter?

Cosmos are annuals; they are

Cosmos are annuals; they are one-season (one growing year) plants; transplanting them won’t necessarily guarantee a repeat performance next year, in a pot or a plot. If you move the plants from the pot to the soil now, and the plants have flowers (which contain seeds) on them—even spent flowers—some of the seeds of those flowers might drop on the ground, survive the winter ,and self-seed as new plants next spring. Pssst: The Almanac forecast predicts a cold winter in your area this winter, and we know nothing about the site conditions of the area in which you want to plant, so it’s impossible to say for certain whether self-seeding will occur.
How about this: try it; you’ve got nothing to lose. Plant this year’s potted cosmos where you want them to grow next season. In spring, buy a packet of cosmos seeds, just in case. That way, you’ll be sure to get the plants where you want them. Maybe even twice as many.

cosmos care (or lack of)

Thoughts: Stop misting. Water very sparingly, just when foliage begins to wilt. Don't fertilize; they need very little if any soil fertility. And give them all-out sun, no shade. Avoid overcaring and practice "tough love" when it comes to cosmos who like to struggle in hot, dry weather. Also, when cosmos grow larger, encourage re-bloom simply by cutting the plants back to 12 - 18 inches high.

Check for burnt edges on the pedals and buds.

Plant lice and midges can give you the sense of over or under watering. Lice and midges plant eggs into flower buds so that the babies can be protected as they eat. This causes premature blooming with the look of burnt edges, deformation and lack of color. Prematurity and burnt edges along with a healthy plant are sure signs of lice and midges.

Step 1. Use a water and dish soap spray or a rose spray for midges and lice on the plant, blooms and buds. Let it dry.

Step 2. Immediately after drying, cut all buds and blooms off and place into a plastic baggie or such. Zip or tie the bag and toss in trash.

Step 3. Spray again to kill any that have fallen.

Step 4. Spray all of your flowering plants in cases any lice or midges escaped and ran to them.

This can be done with all of your flowering plants that aren't for human consumption.


I just measured by tallest cosmos plant. From the ground to the tip of the highest flower, it measures nine feet...not joking . I planted it as part of a plum tree guild