Blind Cosmos

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?

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

Pinch the tops out.

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!

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.

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!

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.

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.

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. 🌸

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

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

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.

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

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.

I was invited into my neighbours today and her cosmos are flourishing with lots of flowers. 🤔

What is the micro climate like where they are planted? Is it sheltered/in full sun/partial shade/exposed as this might have an influence perhaps.
I have done them from seed and planted them out in sheltered garden in partial shade and they were slow to flower, September, whereas the ones I put on the allotment in full sun flowered in August. Uk north midland area.

I think that it was 2018 /9 when I recall many gardeners having blind cosmos .

It could have been caused by adverse weather conditions .
Poor /old seed will cause it .
Poor drainage is another culprit .
The wrong or too much fertiliser .
Too shady a spot .

Pinch out the tops and leave them alone - they just might surprise you !

Pssst, I don’t want to speak too soon but there re buds on my cosmos! Yay! At last

Glad you’ve updated Sidelined. The cosmos in my borders now have lots of buds too and some flowers just opening. The variety I sowed this year are “seashell” and a little different to the usual flowers, but very pretty.

Seashell, sounds very pretty!

In answer to the last couple of posters questions both seed and compost were fresh this year. Grown in trays in the potting shed on a window sill until big enough to go outside then in a sheltered but sunny spot. Tops pinched out as recommended. I suspect it was our odd weather - we had a warm spell followed by a cold grey spell early on, followed by that mini heatwave and now it’s relatively cold and wet again. Ho hum!

We have sown our own cosmos this year and like others on here have lots of foliage but only one flower. Thanks to this thread I think I now know the answer and will tell DH who insists when planting up on adding some compost and fertiliser.

I’ve now got three buds on six plants. Meanwhile, my neighbour’s cosmos are still flowering away beautifully!

Mine are getting well watered today so I'm not going out to look.

I also planted dwarf sunflowers and they show no signs of flowering either.

Well, unlike my dahlias, the cosmos are being uncooperative! Last weekend there were buds looking close to opening … a week there’s no progress! It has been very wet and a tad cold for the time of year but everything else is coping. It’s a shame…😩