Cosmos- what did I do wrong?

[MessySurfaces]

So, I have had a total failure with growing cosmos from seed. I planted the seeds in wee pots last spring, planted them on when they grew (two into a sunny border, one into a pot), they have grown away nicely, but NO FLOWERS. I tried cutting one back, to see if that helped, but nothing. Not even one bud! And now the Sarah raven seed catalogue is mocking me by saying they are so easy and you'll have armfuls of flowers. Not I! I have heavy clay, but I put proper potting compost in the pot and everything!

Clever gardeners, what did I do wrong??? I do love cosmos!

I’d help you but mine were all eaten by slugs

I’m sticking to godetia next year, nothing eats them and they flower easily, even in my cold northern garden.

Yes, I planted considerably more than three, the slugs don't hang about round mine either...

Maybe your compost was too rich. Last year mine grew like Triffids without flowering till September. The reason seemed to be that my new flowerbed was too rich in Nitrogen, which makes plants put on leaf growth.
Try mixing some soil or old compost with new in the pots, next year.
Also the extreme heat has made some of my plants reluctant to flower.

Next year just throw the seeds n the ground

It has been an odd year.

Cosmos grow in the most rubbish soil, we used to just chuck the seeds where we wanted them and leave them to it.

Thank you all- next year handfuls on the ground it is! And I'll keep my fingers crossed in case I get a magical September flush...

Mine were rubbish this year too. I only ended up with one plant from a full pack of seeds, and it’s yet to flower too. You’re not alone op.

Ah well, at least I'm not alone!

Lots of people are having better success with their late sowings (July/August) than the traditional sowing times because of the extensive heat this year.

Try again next year but sow a little and often, every 3 weeks is good.

Thank you- I will do just that

Like JT05 I grew Cosmos from seeds last year and ended up with triffids with no flowers until late August. Honestly, they were 6ft tall! And I'd been so proud of them early on as they grew...and grew😬
Did a bit of research and discovered that the Cosmos we buy in garden centres are usually miniature Cosmos. So I bought seeds for miniature Cosmos to sow this spring. But then I saw small white Cosmos plants at four for £5 in my local independent garden centre in April so I bought them and they're still flowering now.

I’ve planted cosmosfrom seed for the first time this year and they have gone absolutely bananas. Not what we expected at all. 6ft tall and covered in flowers constantly - we can’t deadhead quickly enough.

I’m not just here for the humblebrag but to say we also put some of our seedlings in a very large pot that is more shady (main flowerbed is in fullest sun) and they have given a lot of green growth but only one (really crap) looking flower.

So either in this case - they don’t like the compost I put in the pot and prefer my crappy main soil or they really need full sun to do their best.

Maybe it is the soil one because of the weather this year- it doesn’t make sense with all the previous posters also having issues!

I've successfully grown cosmos every year. However the one lot of seedlings that I planted in clay soil died. The rest have flourished as always although maybe this year not quite as tall

Can you ask a local garden centre for advice? They should be able to answer your questions and recommend effective solutions to your gardening problems. When I purchased some plants in the spring I asked someone working there for advice.
I’m sorry I cannot help you but I have no gardening skills.

I might know the answer. Lack of rain and dry soil caused many of my veg not to sprout, even though I did water them. Every gardener I know had some issues.

Hmm, so it sounds like a mixture of it being a bad year for cosmos, and clay being a tricky soil for them. And bad luck!
Next year I'll try succession sowing every couple of weeks, and I'm working on gradually improving the clay. Fingers crossed...

So, a coda to my failed cosmos story. I just went to pull up the last of the plants, to put in some tulip bulbs. The bloody thing is covered in buds!!!! Great timing cosmos...