Sorry. I was slapped with the surprising admonition that cosmos is not an annual and that I had posted on the wrong forum and that I should bugger off.

Albert,
Huh? Cosmos is an annual : ) Maybe in really hot climates it is not, or maybe certain types like Chocolate Cosmos is a tender perennial, but for most people it is an annual.
I'm not sure how much variation there is. I do know they like it lean and the bigger ones may be in spots with more water and/or fetilizer. Hopefully the big ones bloom soon. I do know they will bloom through autumn and even light frosts.
Remy

My two big cosmos are now 6 and 7 feet tall and still no blooms. They are growing with the others so fertilizer and water are the same.

So, now I am wondering if the big ones should ever bloom (I might still have eight weeks before frost or it might frost next month.) should I make some effort to self pollinate them and collect the seed?

Or is seven foot and a late bloomer still within "normal"?

Persons on Winter Sowing forum are discussing tall cosmos, some that don't bloom before frost. I'm still curious. When do these 6-8 foot cosmos bloom when weather allows?

Most Cosmos are annuals, and most Cosmos are not seven feet tall, but some do get that tall and will bloom if planted in enough sun and the season where you live is long enough. I am sorry you were chastised for your post, some gardeners, like most people are "up tight" sometimes. Al

I live in Arizona and just I few months ago in November my cosmo plant had reached about 8 feet tall and just barely had time to flower before we got hit with a really hard frost that ended up killing half the plant. But never the less I had also had an experience similar to yours and wondered if it was ever going to flower :p I had planted my seedlings in the middle of spring witch for Arizona was around mid march so I would Have expected it to flower much earlier in the season, but I would now say it is quite typical and possible to happen again if you plant during the same time of year some cosmos just don't flower till the photoperiod shortens dramatically.

excessive green growth CAN BE an indication of excessive fertilizer .... especially the nitro side ... as in lawn fert applied to the flower bed ...

this is echoed by the comment above that said:

in order for Cosmos to bloom, it must be neglected. Poor soil is ideal.

fertilizing .. simply for the fact of 'feeding' your babies can become problematic ...

i learned this lesson one year.. when i put FRESH manure all over the beds .... boy did i grow a jungle that year ... at the expense of proper flowering ...

but look out.. the following years i had super soil ....

ken

Hi there,
I think I remember from some German book on annuals that Cosmos used to be/are a kind of "short day plant" meaning they require rather short days to induce flowers. So that means after the summer.
The modern or present cultivars are bred for earlier flowers and often for shorter stems (better for small gardens, less flopping over...).
So could be that the tall ones are of the more old fashioned kind, reverted to the more native type by mutation or whatever.
I watched some Cosmos grow and flower happily in a friends allotment last summer, on heavy clay soil, lots of rain, so no starving for those.
Bye, Lin

There has been a thread about this same issue on the wintersowing forum since last summer or even before. Lots of people experiencing very tall cosmos with no blooms for extended seasons. I've had the same issue with all of my cosmos--probably because I'm growing seeds that I collected late in the season from some of these tall plants.

Martha

Last year, 2010, some of my tall cosmos were just beginning to bloom when we got our first serious frost. I cut off the tops of some and put them in a vase of water. I got blooms with seed and vigorous roots. I could not keep the rooted cuttings alive.

Some of the seed that matured inside were viable and I now have cosmos blooming in pots in February inside. They are not particularly impressive but it is happening nonetheless.

Cosmos with little water and poor soil will grow up to 8 feet tall and bloom late unless they are the varieties that have been bred to be shorter. I grew them last year with NO water and NO fertilizer and the orange and yellow natural variety grew almost 9 feet with no blooms until August(with some very hoary thick stalked bushy ones at 10 feet that only bloomed almost a week before frost in October. The same seeds with water and fertilizer grew only three feet and bloomed in July.

I'm having the opposite problem.My cosmos is only 5 or 6 inches tall and now has started blooming. We had a cold wet spring and summer heat then hit us hard. I'm hoping their strange behavior is the result of the weather and not the gardener -- although I can't think of anything I've done that could stunt them so.

I usually sew a few packs of cosmos every year. Last year I got several 5 and 6 foot plants. They flowered the same as their smaller brothers and sisters. Sur
e was cool to have those cosmo "trees" in the garden. :)

Maybe my ground isn't radioactive after all! I planted Bright Lights and a purple mix in the spring and they grew to three or four feet. As they finished, new plants quickly grew under them from the seeds they set. The tallest is now over seven feet and they are covered with flowers in various shades of orange. And they're still coming up everywhere. I just cut the ones in the picture today. I'm hoping they'll continue to naturalize because I love cosmos! I'm in Central Florida.

One of my tall cosmos near a sprinkler fell over a couple of months ago and has rooted in several places and has put up several shoots near the nodes that rooted. Now there are many fine flowers from these shoots. These flowers are larger than the other on taller stems nearby.

I have very rich soil and my cosmos do fine. They are in full sun. The grow quite tall and begin blooming in August until a heavy frost kills them. (I do pinch them to encourage lateral in July).

It's always good to know we're not alone when something in the garden acts weird! I planted an orange-flowering cosmos years ago and let it reseed on its own. Sometimes after the earliest plants went to seed & looked ratty I'd pull them up and let a new crop grow for fall.
But like passion4tropicals, this year the early plants were normal height & were blooming & setting seed by mid-May. Now in July, the second crop of seedlings have become enormous without a hint of a bud. I don't think much has changed in that bed, but now I'm wondering whether the original seeds were a cross, and these titanic Cosmos are actually one of the parents.

Annie at the Transplantable Rose

Just wait. Those really tall ones will have 100 flowers. Every year someone posts here about those tall ones. They just take longer to flower. But what a show.

Thanks for the answer, Susanzone5. There were too many large seedlings for the space & they were shading out everything else, so I pulled some, left some, and will now try to be patient!

I sowed seeds for six cosmos plants indoors on 4/28/13. They all varied in height and bloom time. My tallest started blooming on 9/30 (which is just bizarre). At 6.5 feet, it is absolutely statuesque.

How funny, SingSk8! We're many miles apart but the first buds on my weird cosmos formed the last week in September and are in full bloom now. One is over 7-ft tall and others might have been taller if staked - instead they've been bent over by wind & rain.
In the meantime, other self seeded plants popped up, stayed under 20-inches in height, and bloomed in early September.
The giants are fun & interesting, but the 2-ft plants fit the bed much better.

Annie

I was so happy to find this forum a couple months ago when my 2nd generation cosmos plants here in AZ were getting huge without any buds.. so I gave them time and sure enough, buds started appearing in Sept and are now in full bloom, mid Oct with more plants spreading across our gravel front yard. They are so hearty and easy to grow and originally came from a wildflower mix from High Country Gardens that took off after the others died off, along with Indian Blanket flowers that look great together.

I have 8 ft ( and over) cosmos that bloom in Sept and Oct ( weather remitting in N. Minn.). Love these flowers! Oh--- and I collect their seeds and grow heritage plants every year.

We had grown tallest Cosmos plants to the height of 11.5 ft. and 14 ft 3 inch. in different years.

9 Balsam plants grown to more than 10 ft tall. All in pots.

One French Marigold plant covered an area of 105 sq.ft..

One Balsam plant covered an area of 50 sq. ft.

We couple, Balaji Dakoju and my wife Padma Dakoju speak to the plants and request them to grow taller and wider.

The plants responding to our requests.

We love plants. We treat them like our children. We have great experience with plants for the last 32 years.

Hundreds of plants responded. They show their happiness in their growth.

All these plants for all these years we are growing in rented houses in a open yard. . Sometimes growing plants in pots, keeping them on side of footpaths without disturbing the pedestrian in front of our house due to lack of place

We are happy to share about our plants with you all.

Thank you.

Balaji Dakoju.

Mobile: +91 9880819920

We live in Central Texas, very hot summers but we try to keep the garden wet. Many, many years ago I planted some ornamental cosmos thinking they would be the plants that get 2 feet or so. Not sure why, but some went crazy and grew to 8 to 10 feet...we didn't know what the heck they were until fall when they bloomed...and boy do they bloom...the Monarchs and humming birds migrating through love them. They seed so much that we pull the plants up EVERYWHERE, but we leave several plants or a patch of them in the garden....just for the fall show they put on. We have so many comments on them from folks passing by. A wonderful plant!

IIMM

I've hygrown some cosmos in some huge deep pots and another few in smaller pots... The one in the deep pot with lots of compost produced few flowers through June and July but since August they have been flowering continuously as long as I keep deadheading. They're about 6ft and are still going strong.

The one in the small pots grew nice and round and short with tons of flowers but tiny in comparison to the large flowers on the big plants.

The larger plants had marginally less flowers and were smaller but much better looking plants and flowering later on in the season. I fertilised all of them too.

I think the bigger or more space you give the plants the larger they are with more foliage and the smaller the pots are the more compact with more flowers but smaller.

I bought a dollar general box of flower seeds and sprinkled them in my garden. I had no idea what this one 7 foot monstrosity was until it bloomed. My family wanted me to pull it up, insisting it was a weed. I just couldn’t do it and now I’m rewarded with beautiful white flowers and the joy from having the patience to see what would happen….these Cosmos are beautiful!

I've grown the Sensation Mix cosmos and got huge ;plants that didn't bloom till fall. I bought Dwarf Cutesy cosmos which starts blooming in May and stays a nice height...about 3'. The dwarf types have consistently bloomed earlier.

Hello Tenessa R,

" ...and now I’m rewarded with beautiful white flowers and the joy from having the patience to see what would happen….these Cosmos are beautiful! "

It is the middle of Winter here in Kansas. You must be in the Southern hemisphere.

Am I wrong about that?

ZM

Hello erasmus_gw,

" I've grown the Sensation Mix cosmos and got huge plants that didn't bloom till fall. I bought Dwarf Cutesy cosmos which starts blooming in May and stays a nice height..."

I suspect that not blooming until Fall suggests a strong Photoperiod Response of not blooming until the dark period is longer. I have never grown Cosmos, although those huge plants are a temptation. I grow and breed Zinnias as a hobby and they bloom early like your Cutesy Cosmos, which could be a Photoperiod thing. I probably should do a little further investigation into Photoperiod. I seem to recall that what is usually regarded as a Long-Day photoperiod is actually Short-Night, but I could be wrong about that.

ZM