September 21st, 2007
Cosmos, the Tall and Short of It

Cosmos sulphureus
2007-09-21. Differing habits of Cosmos sulphureus despite being from the same seed packet and planted in the same site.

I planted a packet of orange cosmos, Cosmos sulphureus, early last summer and the seeds sprouted and grew during our very rainy June. When I returned from vacation in July, the meadow was populated with lots of cheerful orange flowers growing on plants with a branching habit about three feet (1m) tall and wide. Those plants are just now starting to look a bit ragged.

In their place Super Cosmos has sprung up. These are orange cosmos on an incredibly thick stalk. The first one shot up to almost 6 feet before flowering. I had to stake it, as it was leaning precariously. I thought this was just a freak but all the orange cosmos coming up now are following the same pattern.

All these cosmos were planted at the same time from the same seed packet in the same location. I have not fed them anything. (Most wildflowers thrive on poor soils; feed them and you’ll get a lot of green and few flowers.) I have not given them supplemental water, as we’ve had so much rain this year. And yet they look like different plants. Were there different varieties in the seed packet? Did the early sprouting type have a different habit. Are they responding to the different amounts of rain we received at different times over the summer? Or did the ones that sprout earlier grow differently because of the time of year they were growing? I read once that cosmos grow best after the summer equinox. Certainly the plants that sprouted before the equinox behaved quite differently than these that sprouted after.

This is the first year I’ve grown orange cosmos. (Pam/Digging assures me it won’t be the last as they are prolific self-sowers.) So I have no basis for comparison. How do your orange cosmos grow? Short and wide? Or tall and straight?

by M Sinclair Stevens

42 Responses to post “Cosmos, the Tall and Short of It”

  1. From Pam/Digging:

    That’s exactly what my orange cosmos did. I always had several “strata” of cosmos, and by the end of the summer, the top layer was as tall as I am (almost 6 feet).

    I sowed the initial crop from one seed packet. That fall, I intentionally scattered seed from the seedheads throughout the garden. I never had to do it again, as it self-sowed exceedingly well. When I cut it back in the winter and dragged the stubble out to the bin, it self-sowed along my path as well.

    Interesting. So I guess I haven’t discovered a strange strain of Super Cosmos. –mss

  2. From Steve Mudge:

    To compare, we planted okra too early, in April, and again in June. The early okra had spindly, veiny leaves while the June crop had fat lush green leaves. Even with all that rain the early crop never changed the way it grew. The same DNA (genotype) can elicit several different physical representations (phenotypes), depending on the conditions under which they are grown.

    That’s a mouthful, Steve. I think you’re on to something. I’m going to start experimenting with my sowing dates now. — mss

  3. From Annie in Austin:

    This is kind of cool – I can see this will be an ongoing experiment, MSS!
    The shorter orange cosmos could fit in my garden, but I have no idea where to put a six-foot orange flower.

    Annie at the Transplantable Rose

    That’s how I feel. The three-foot bushy cosmos were just perfect for the middle of the meadow. The six-foot tall ones look like ominous sentinels. But I’m happy to have any flower so I won’t be taking them out even if they don’t “fit” in the scheme. I’m a plant person more than a garden person. –mss

  4. From Yolanda Elizabet:

    I don’t grow this variety of cosmos but have noticed that plants can turn out very differently from the same packet of seeds. I’d sown some deep purple pansies in Spring and most of them were deep purple but some were yellow and red.

    The surprises you get in the garden eh? 🙂

    Absolutely! Surprises makes gardening interesting at every turn.

  5. From Libby (Austin):

    It’s my totally uninformed opinion that the giant cosmos are actually retrogrades to the true plant form from which the hybridized seed was derived.
    As long as you put them behind where they can range freely they can be a welcome burst of dayglo at September.
    I first collected seed from a plant that was:
    1. growing from a crack in a concrete retaining wall on South Lamar in full sun
    2. blooming in July

    I figured any plant that tough was my kind of plant. Even though they self sow prolifically the baby plants are easy to pull up if you don’t want them.
    Their only downside is the color, the screaming Cheeto orange is not for every garden spot.

    Hey, Libby. Nice to hear from a new voice. Especially another Austinite. Like you, I don’t mind self-sowers. I think it’s easier to pull out what I don’t want than to try find plants to fill in blank spaces. I don’t find the cosmos a hard orange to blend in the garden because the plants are so airy and the flowers small–not like marigolds or mums. I have quite a mix of shades of orange, even a bicolor and a lemon yellow. — mss

  6. From maryline (toronto):

    These freakish mutants are growing in my garden as well. Three cosmos grew from a seed packet I randomly scattered on the garden (early June) and they have thick stalks like sunflowers. They have all had damage to the bottoms of their stalks and to some of the heavier bottom branches. I pulled the branches off. However, one cosmos has only bottom branches left. Months of growth later (Sept 30th) my cosmos have just started to produce buds and one purple flower just appeared. I was going to pull them out because they are so tall but no flowers. The tallest one is 6 feet and the top looks like cookie monster with a series of cable-like branches all connected together. Weird, but I’m so happy to finally see flowers. Also, my tallest fell over and I staked it and noticed ants all over the wound at the base (black and hollowed out a bit).

  7. From firefly (maine):

    Well (as you know, MSS), I grew white cosmos this year. They started blooming when they were short (about 2 1/2 feet) and kept at it all summer, and are still blooming now that they’re taller than I am.

    The Ammi I started from seed, though, had two different forms — one like the catalog description, big round Queen Anne’s lace heads, and the other in a looser form with somewhat different leaves.

    Now you’ve got me curious and I think I’m going to e-mail Select Seeds to see what they say about the two different Ammis.

  8. From Bob Pool:

    My orange cosmos does almost the same as yours.The short,early bloomers only get 18″ to 24″ tall and seem to wither in the summer heat. But the others don`t bloom at all till late September and after this great summer we have had they are now close to 10′ tall and magnificent.

  9. From Connie Kupke:

    I got a packet of these mixed size orange cosmos flowers in Bastrop County, Texas a few years ago. I dropped a few saved seeds in a pile of excavated clay at our new home in Denton County. I have pretty much ignored them in the 12-14 hour sunlight with little to no feeding or watering. They are just starting to bloom with tons of buds. We enjoy speculating where the giants came from – the package said they would grow to be 1-3 ft tall. What an easy way to draw butterflies and other bugs into your yard!

    Thanks for sharing your experience. This is the first year I’ve grown them and it’s great to have flowers all through the summer. Most of my other annuals bite the dust by Father’s Day. Isn’t it great that the butterflies love them. I’m so glad that they’ve found something they like as my little scarlet milkweed doesn’t get many visitors. — mss

  10. From Kathy (New York):

    I really enjoyed seeing the cosmos in person. Weather and climate have a profound effect on plant growth, but there are so many factors it can be difficult to see the cause and effect relationship. I am still trying to figure out why my bloom-on-new-wood macrophylla hydrangeas didn’t bloom, and why my colchicums are blooming later than usual.

    Gardening is never dull.

    I was so glad to meet you. Thanks for stopping by the garden…and for the little candle. It’s lovely. A new batch of orange cosmos is coming up from seeds thrown off by the first batch. Flowers are starting to form on plants only a foot tall. This makes me think that an important factor is the amount of rain received. — mss

  11. From Robin Tucker-Little Rock, Arkansas:

    My wife and I have these orange mutants as well. This will be the third year.They showed up the following year after my wife put the packet seeds in one of our beds.tThe first year we had no idea what they were and pulled them up except for one plant(curiosity). now they sprout everywhere and I mean everywhere.This year we saved six plants and planted them behind all our mexican sage which blooms about the same time.brilliant contrast of color.They are monsters but they will bloom until first frost.We think they are great.Wonderful late summer early fall butterfly magnets.

  12. From Talia (East Texas):

    I planted a package of cosmos from Wal-Mart and got a sulphureus and a bipinnatus. The “super” cosmo is topping six feet, maybe even at seven now, it’s kind of hard to measure! It hasn’t budded or flowered yet, but the spiders have made a pretty home in it!

  13. From Catherine Tucson, AZ:

    When I first saw a giant cosmos it was seven feet tall and full of flowers and seed…a few of which fell into my pocket. This Spring it sprung up amongst other wildflowers. And it grew quickly- to over five feet tall. Beautiful! My friends and I pondered our gorgeous monument as no sign of buds were evident. We adored our plant; waiting for flowers and seed to share. No…not yet. We were patient. Maybe make some bets as to when the first buds would appear? Oh so patient. Then, SLAM, overnight somebody stole our precious angel- cut her off at the roots- ouch. My only conclusion is maybe it was mistaken for Good Smoke???? Such a loss. Mostly we all were deprived of fruition…seed to try again next Spring. Can anybody help? Our loss hurt but heck, it’s great if you can help us try again.

  14. From Terese (Chicago, IL):

    I was doing an internet search on this very topic. Is there a difference between “Giant” cosmos and ‘Cosmic Orange’ (the ones i bought at the store)?

    My “Giant” or “Super” were HUGE. I had two of them, where all the others were between 10-30″ tall, these were 4-6 feet…. same late bloomers, covered in spiders and thick like a sun flower.

    Very weird.

    Glad I found this thread.

    Different seed companies select flowers for specific attributes. My cosmos were Cosmos sulphureus ‘Bright Lights Blend’ from Botanical Interests. Being a blend, the packet produced plants of various sizes and flowers of various colors, supposedly brighter than the average cosmos. Your ‘Cosmic Orange’ is a selection by Park Seed, selected for its double and semi-double orange flowers. The plants are supposed to be about two feet tall. When I referred to “Super Cosmos” I was not referring to a specific selection; I was simply employing poetic license. — mss

  15. From Cathy Stewart, Sydney, Australia:

    Fascinated to read all these giant cosmos stories. Last November (southern hemisphere timing!) I scattered orange cosmos seed to fill in my orange summer garden of Dicliptera, marigolds, Dahlia and Gloxinia. About half a dozen small plants came up and flowered at about 60cm (2 feet)……and then, just as they were dying back…… 2 enormous ‘triffids’ sprang up and just grew and grew and grew to well over 2 metres (7 foot). They’re just flowering now in early April and look spectacular – if only they were further to the back! Glad to hear I’m not harbouring some world first mutation or have some steroid drenched soil. Would have been fun if the flowers had been proportionately sized. I shall investigate this further with some botanist friends and try and find out WHY.

    That’s always my first instinct. I want to know WHY. If you find out more information, please share it. — mss

  16. From Heather:

    I think that gardening is NEVER boring. After all you need lots of patience to be a good gardener. Genrally, cosmos are my favorite flower by far.

  17. From karen north carolina:

    I really think something weird is going on with bright light cosmos. I’ve been growing them from seed for at least 20 years and they have been a predictable and lovely front of the border filler, blooming mid-July till frost, reaching 2 to 2.5 feet. Last year they got huge—5-6 feet tall, with tree-like “trunks”— and not until late September did I get a pitiful scattering of insignificant blooms. I’ve not fertilized or otherwise changed their growing conditions. This year the same thing appears to be happening. I have to cut them back because they’re hiding the plants that ARE blooming, and even the ones I haven’t cut back have not produced a single bloom. What on earth has happened to bright light cosmos??

  18. From Joann- Reno Nevada:

    The above experiences mirror my own. I thought it was a problem with me only, or my packet of seeds. The problem with the huge plants is that they block out my other flowers, even now when they are about 3 to 4 feet tall. Last year I had only the shorter variety, with many bright blooms, and that is what I expected. I did get some like these, but also a great many treelike, so far budless plants. Reading the above, this seems to be a very widespread phenomenum. I think I might have to get rid of most of the giants, as they are mainly in planters and large pots with other flowers, and are drowning them out.

  19. From karen north carolina:

    As of today only 2 of my 16 cosmos bright lights have flowers, and the other 14 don’t even have buds. And again this year they’re gigantic, overtaking every bed they’re in. I’ve corresponded with the seed company, Terrestial Seed, and a month or so ago they said they hadn’t noticed anything unusual in their trial gardens. I find it hard to believe I got the only 2 Territorial Seed packets (this year and last year) that produced these freaks.

  20. From Monica(Scurry,TX):

    I also have a cosmo that keeps growing and growing.Right now it is about 8 feet tall and not a sign of blooming or slowing down.I have 1 smaller plant blooming it is a pinkish-purple.I bought these seeds at Wal-Mart.I have never seen a flower get so tall

  21. From Tom Ft. Worth, TX:

    I grew orange and yellow Cosmos this year in untreated soil. I had a few of them that grew tall with no blooms so I deadheaded it at 2ft and it went ballistic branching out and blooming like crazy after that. The taller ones were also the second round of cosmos that had sprung up later in the season. These had a maximum of 3 hours of solid sunlight and turned out excellent. I’m curious as to how well the seeds will handle our winter as I read they are not winter hardy. What a bargain with 5 solid months of blooms. 🙂

  22. From chris mccasland brazoria texas:

    Mine did the same thing. the second year, the seeds of the yellow and orange cosmos that fell into the gravel driveway in the worst possible soil got to 7 to 8 feet tall.

  23. From Ruth from Ottawa Canada:

    Well was I happy to see comments on giant cosmos. I picked up a packet from a dollar store a couple of years ago and was so pleased and surpised at how giant they actually were. I started them indoors last year and was I glad I did, as the self sowers took considerably longer to come up. But what I was really surprized at was I planted some in long rectangular planters in front of a tin storage shed. and like some of you have stated, these grew exceptionally tall and didn’t bloom until way late in the season. I figured it was due to a combination of full sun and heat emanating from the shed??? I’ve had to change my gardens due to the fact that these plants drown out everything else. But I love them so! Everyone comments on the orange colour and the look of the plant and I have given many seeds away, however I would now like to try and find another colour. What else is there in the giant variety…white and purple?

  24. From Sheila-Mason, MI:

    I have Cosmos that are taking over all of my beds. I have really pretty perennials-lavender, catmint, etc. but I can’t see them because of the Cosmos. How can I control them? Do I need to pull them up or move my perennials?

  25. From Doris-Panama City Beach:

    I thought I had a wonderful freak growing in my garden; I’m happy to hear that others have the same plant – the giant cosmos, the only one among many small plants. It is loaded with buds and blooms. A lovely gold color. This is such a pleasant surprise. How do I salvage seeds for next spring?

    Just wait until the seeds ripen. They will be hard and black. Usually they will self-sow, too, so you’ll have cosmos popping up everywhere. I just move them where I want them. — mss

  26. From Mary Lou-La Mirada, CA:

    I’m happy to have found this thread. We weren’t sure what we were growing but suddenly we had a crop of exceptionally healthy-looking plants throughout our garden. I thought I’d planted Shasta Daisy seeds. These plants seemed to be growing right before our eyes. We attributed it to composting and a leaky soaker hose. When the plants reached about seven feet tall we didn’t think they were the daisies. We recently noticed a few buds beginning to open but now I realize we have a crop of Super Cosmos. My boyfriend just measured the tallest plants at 10′ tall! We’ve decided to let the plants bloom but I’m hoping to remove them before they reseed because I don’t want my garden to be taken over by giants. My neighbor is fascinated by the size of our super Cosmos! They are still growing taller!

    Thanks for sharing your experience. I don’t mind most flowers reseeding because it’s easy enough to pull them out or move them where I want them. My entire garden is “designed” on this practice. I couldn’t afford to have a garden if I didn’t have so many successful self-sowers. — mss

  27. From Mary Ann in Sugar Land:

    I am thrilled to find these posts in response Googling “giant second growth Cosmos!” Mine are taller than me and amazing but not yet blooming. We had a much wetter July than usual, but now in the throes of August 100 degree days, these plants look like I fed them super vitamins.

    I’m glad that we’ve shared a common experience. — mss

  28. From George in Chicago:

    I too have discovered a giant cosmos growing amongst the regular size cosmos and I feel like Jack and the Beanstalk has come to Chicago.

    It’s presently over 6 feet tall without any buds at the moment but cannot wait for the blossoms!!!

    The plant itself looks beautiful and I’m anxious to see what color the flowers will be and plan to keep seeds as well as spread some around this fall.

  29. From Katherine in Schaumburg:

    I also have this monster cosmos which just today displayed one single purple flower. It has a VERY thick hairy stalk, is heavily branched (3 1/2-4 ft wide) and is about 6 feet tall. Last year I purchased white cosmos from the Home Depot. The “new guy” is a self seeder or volunteer from this stock.

  30. From Rebecca from Dallas:

    HI! — I’ve been so glad to find all these comments, because I’d started wondering if my cosmos plant had somehow merged with a sunflower plant, of which several are also growing close by, or if the ground had mutation-causing chemicals or radiation! I love the plant — the way it looks — it’s thick and ferny and deep green — no buds or flowers, but judging from what your other guests have written, those may still come. I loved the other cosmos, too, from the same seed packet, but they were much smaller and are on the way out here at the end of August, but oh! they had dancing, joyful golden flowers! Thank you for your site!

  31. From Pat in Florida:

    I was just about to dig it out. It looks like ragweed, but the leaves are exactly like the cosmos. It’s the only really giant specimen I’ve seen in at least five years of volunteers. Guess I’ll wait to see if it blooms. No bud, Sept. 3, plant 5 feet tall, needing a stake. Lost among the passionflower incarnata vines.

  32. From Tom:

    I live in northeast , ohio and have a cosmo plant/flower over 109 inches tall, and it is BEAUTIFUL!

  33. From Ethel Nylund:

    I couldn’t figure out what these flowers were, got them from a packet of cosmos. The leaves are not like the cosmos but like a ragweed. Mine didn’t bloom in time for butterflies to be attracted to them. They are now about 8ft tall and are still growing. It it is almost time for frost here so they will not be growing much longer. I am going to collect some seeds from them for next year. Thanks to everyone who got the same ones now I know what they are.

  34. From eileen, nj:

    I bought a pack of cosmo seeds at the dollar store for 25 cents. sprouted them inside in april, transplanted them outside by the walkway. but they had no flowers. they shot up to 7 feet tall, i had to keep tying them back to clear the walkway! stalks are 2 inches around and they keep growing even as they get pulled and twisted-some stalks knocked horizontal by the wind are now growing up vertically from the main stalk! but not a flower until the end of september. they’ve been covered in blooms the last 3 weeks. amazing! 🙂 will def harvest these seeds!!

  35. From Vicki Pepper:

    Hey everybody try googling Giant cosmos – These are not mutants – but rather a related family of Cosmos that once were the most popular kind. Then they were hybrid to make them smaller and more compact and for a time these became the more popular version because not too many people can fit in 6 foot plants in their gardens. I grow giant ornage cosmos every year because here on the Pacific Coast they bloom right through Oct and Nov. Makes for great fall color through the holidays.

  36. From Martha Lakeview, Ohio:

    I planted a package of Cosmos and they were bright lights mixed on the 21st of March. I have some little sprouts that look like weeds, is it possible that it is the Cosmos making a appearance?

    Anything is possible. Sorry I don’t have any photos of cosmos sprouts to share. — mss

  37. From Sharon/Ithaca, NY:

    I’m bewildered by the similarity of leaves in the ragweed and orange cosmos. The plants grew side by side until about 4 feet tall when a bunch developed bountiful beautiful orange flowers and the others developed the ragweed “flowers”. They looked identical until then. How is this possible? Is there some identifying mark I am not registering before the flower stage so I can pull the ragweed?

    It’s also strange to me how the leaves of this orange cosmos (lobed, like ragweed leaves) are so different than the ones of my other purple and pink cosmos plants (a wispy/feathery look.)

  38. From Meg:

    I finally decided to Google this plant and see if there were others who had the giant plants. I’m surprised to find so much information.
    Mine came from a free package of seeds sent in an ad I received last year.They grew normally (small) and bloomed. Then some of them began to turn into giants, about 6 feet tall. I thought I had some kind of mutation.
    They reseeded themselves this spring and some are even bushier and more lush than the last ones.
    The smaller version reseeded too, but only a few of them came up as opposed to the large ones.
    It’s interesting to know that the large ones were the originals!


  39. From karen mulhern Vero Beach, FL:

    just read through this entire “mutant super cosmos” thread in an effort to find out why my seeds grew this crazy way. my plants are between 6-9 ft tall with no flowers yet, but they look incredibly healthy despite outrageous tropical heat. just wanted to say hello! Its been 4 years since the first post in this thread btw!!! i guess these huge plants are here to stay!

  40. From Martha Lakeview,Ohio:

    I now have several Cosmos that are VERY tall, one is taller than I am, I looked at them yesterday and I have 6 buds on them! I am glad I found this website and read that other people have these giant orange Cosmos plants. The one that is taller than I don’t have buds yet, but several of the others do. Hopefully they will bloom before the frost gets them, we are supposed to get quite a bit of rain the next few days, do you think that will delay blooming? The one plant I looked on looks like it has 3 buds on it, tomorrow I am going to tie a wire from one side of the lattice to the other to help hold them up, thanks for having this page. I was thinking of putting a thin layer of potting soil around the bottom of the Cosmos plants, what do you think?

  41. From Martha Ohio:

    My Giant Bright Lights Cosmos are budding now, the tallest one is taller than I am. I was wondering, the plants that are not budding, would it be a good idea to cut them back, they are pretty tall. The one that is taller than I am, would it kill it if I cut it back some? The bottoms are looking rather scroungy, but there are some green on them too. Anxious to see how big the blooms will be.

  42. From Darrell:

    I’ve been looking for the giant Cosmos sulphureus seed for quite some time and it looks as if it is becoming too hybridized. I wish that they would just leave the cross-polination up to the bees and not create a bunch of mutants. Over time we could loose the oringinal species if we become
    distracted and delusionized by the tinkering results of the the human made culture.