Has anyone planted Cosmos, and had some not bloom?

Question

I am guessing they didn't get pollinated. I have six plants and only two bloomed, the other four are duds. I don't know what happened.

Answer 1

No, pollination occurs when the flowers are open. How well did the other two flower? If they did well, then the four that didn't have some problem......perhaps kinked roots that just didn't feed the plant well enough to make enough carbohydrates to allow for flowering. If all had failed to flower I'd be looking at a fertilizer mishap.......say way too much nitrogen which tends to promote leaves, not flowers.

Answer 2

you may have planted too late in the season for all to bloom