I have grown Cosmos from seed, they are planted out in the garden but just keep growing, some are 3 ft tall, lovely bushy plants but no flowers, what can I do to encourage them to flower?
They will flower. Just give them a feed of tomato fertiliser to encourage flowering. Too much nitrogen and they will grow huge before eventually flowering.
I've been waiting a while for this one to flower now it's 6ft 6-
Keep dead heading too, the more you do, the more flowers you will get. I've grown them from seed for the first time too and have completely fallen in love with them.
Im definitely growing again next year, the bees love them and get cross when I'm dead heading the flowers. I now do it in the evening when not so many are about.
I am still waiting for my Cosmos to flower & they are now 5ft tall!
Have you got flower buds, are they in the sun?
I'm growing 'Dwarf Cosmos Sonata mixed' and they are only dwarf compared the the 6ft monsters (ie the normal types I usually grow!) These are 3-4ft and most are now in flower but it was a long time coming which I'm putting down the the weather - just not a very warm summer which is what they need and get in their native habitat (Mexico.)
Finally my Cosmos are in bud & about to flower.
Better late than never