Blind Cosmos

I love cosmos and grow them every year from seed but often there are several plants that grow very tall and bushy and do not bloom until late summer. The ones this year are at least twice the size of their brothers that are in full bloom but there is not yet a bud on the monsters. No idea why.

My cosmos isn’t flowering either big and strong but no buds at all.
Also put in decent soil ....

They’ve been good in the last couple of years so this lot are disappointing. Two years ago I planted lots of new tulip bulbs in pots and every one was blind! That was very disappointing and I’ve not bothered since. Well, I like the greenery too so they’ll stay in my display and be space fillers.

Thank you.

I grew lots from seed last year - they grew huge and lush - hardly any flowers at all! I haven't bothered this year

I planted seeds ages ago, and so far they're about 4" high!

Casdon

They don’t like rich soil, have you got them in potting compost rather than straight in the ground, or have you used plant food on them?

Oh no! I’m a cosmos novice and planted mine into containers with compost last week! The label didn’t say anything about conditions. Oh well, they were only £4 for six and the greenery is nice to look at. 🌸

It's funny OP but a few years ago I recall that a local nursery (when I lived in Devon) found that they'd got 'a bad lot' of cosmos because hardly any of them flowered - rather odd. Normally, they'd have had a really lovely display by their main entrance. It was rather disappointing and puzzling. I wonder if this is a repeat of the same problem which they never got to the bottom of.

Mine are all out, I sowed them in March in the coldframe. The hot weather brought them on, but they should be flowering by July normally. I’m a bit disappointed as I sowed some which were meant to be blush coloured, but they seem to be white.

None of my cosmos have started to flower yet, the ones in the borders aren’t even showing buds yet. I do have flowers on the ones potted up with compost in containers around the terrace. They’ve all had a weekly foliar feed with seaweed or comfrey for the last few weeks. I think they’re all a bit late this year!

Germanshepherdsmum

Pinch the tops out.

That will give you more flowers, but if you haven’t got any at all it’s definitely the compost.

Yes. If you can replace a portion of the potting compost with soil that would help, and the potting compost loses the nitrogen after about 6 weeks, so they will flower, just later. They are one of the ‘treat them mean, keep them keen’ plants!

Pinch the tops out.

Potting compost, no plant food. Is there any hope?

They don’t like rich soil, have you got them in potting compost rather than straight in the ground, or have you used plant food on them?