What kind were the ones you planted from seed? I grow huge beds of cosmos and every year the Sulphur Cosmos are the last, and the tallest to bloom for me.....usually after all the others have faded away. The Sulphur Cosmos, such as Bright Lights have just started to bloom for me a couple of weeks ago here in Zone 8.
Alice

Common problem in good soil or with too much fertiliser. Cosmos do best in lean soil and even then you can expect some varieties to exceed three feet in height. Many of the named cultivars are bred as dwarfs, but where's the point in that :)

I didn't keep the seed packet with the info on it, darn it anyway, I thought a cosmo was a cosmo was a cosmo, wrong ! Oh well, I am happy with it and if it does bloom I will have some big comos next year, if not hopefully I will remember the packet when I see it or just read the back for the height. It is definitley in poor or "lean" soil not a lot of fertilizer, just a good ole gal I guess. Thanks.

I had some huge(6 ft. tall) cosmos bloom last fall after the first light frost. It was in a weedy area that had had some wildflower seed spread out over it a few years back. It took the name that plant forum to identify it because I have lots of cosmos sulfurus which is a completely different plant. (different type of flowers, different type of leave, different growing habits)

Here is the picture I submitted to the NTP forum:
{{gwi:247576}}

I guess, just don't give up on them blooming yet.
JP

Cosmos bipinnatus is the big one and comes in a range of shades from white through pink to red. I think there are some doubles now too. Most hybrid cultivars will not grow to six feet but the species will.

I have the same problem as maininmontana. My cosmos are huge, almost 5.5 feet tall with no blooms. Strangely, one of the plants is blooming white flowers. I did fertilize the flower bed they are in and so it may be because of that. I distinctly remember reading on the seed packet the plant height as 3feet maximum, they may be bright lights (I am not positive about it). What should I do now, get rid of them, are is there hope for me. Thanks in advance.

I have a app called google lens that identify anything you take a picture of.I found the most beautiful flowers but it was so dense and tall that I thought it was a bush. It was 7ft. Tall. It showed through the app it was Cosmos. Do they normally get that tall? I remember throwing a $1.00 packet of seeds I got from the Dollar Tree. Never in my life did I think they would take off. I am so new to flowers and plants. I am so happy to find that some of you have had taller Cosmos. I would like to ask what would be a good book or site to find out more about plants, flowers, bushes that I could plant.One that would teach me to take care of them.

Same issue here.

did you cut/pull the stocks?

of course all flowers died but the stocks are still there.

should i pull them out or cut them?