I don't know if it's normal, but things like that do happen occasionally and are inexplicable. Maybe cut them back halfway see if that stimulates them to re-boot.

There have been lots of reports on several forums over the past few years of the tall, pink varieties of cosmos taking forever to bloom, or not blooming at all. Most often it occurs with seed that has been saved from previous years. I wonder if the plants are reverting to some wild type that is day length dependent for blooming. Anyway, it's not anything you are doing wrong.

Martha

Thank you for your replies. Maybe I should hit the non flowering ones with some sulphate of potash. It seems like I've got nothing to lose.

In northern MN, the pink variety (standard) does not bloom until toward late summer/fall. I have planted them for years and never had them bloom at any other time no matter when they were planted out.