it seems like it's doing really well, but no sign of any flowers yet. Should I be concerned or just patient? I live in Cincinnati - Zone 6. I put the football in the picture so you could see how big the Cosmos has gotten.

They sure look like they're ready to me. Are they maybe getting too much shade, Gary? I see in the picture most of the street is in the sun but the cosmos plants are shaded. They really need some sun to bloom.

If that's not the cause, well you can try scaling back on water just a bit to stress them into blooming. Don't let them completely wilt, but let them dry out a bit.

I've had the same problem some years. Same treatment, same flower bed. I once went looking for answers and found this theory from several years back in the UK:

http://www.telegraph.co.uk/gar...

I have 1 big plant from scattering seeds in the spring, just now starting to bloom a vibrant fuchsia color. They weren't any particular kind, just "cosmos."

See Figures 2 and 3 in this article. My understanding from the other article I posted is that the cosmos seed source influences whether they are short-day or not. I don't know what the critical daylength for them is but the days are starting to get shorter now.

https://www.extension.purdue.e...

In Gary's case I also wonder if there might be some influence from street or house lighting at night.

Fascinating! My plant is in the front yard, and there are street lights.