Centura is a perennial Cornflower but Cosmos def Annual.
My Cosmos this year were not sown until May, as illness and builders left me up a creek. They have grown BIG and some have plenty of bud and a few flowers, others don't have anything showing yet except big healthy plants. I'll try and get a pic or two later to show you.
My half hardy annuals have done well this year given the late start (again not sown until May), but probably a good thing considering the cold spring.
Hardy Annuals, rarely need the protection I afford them, but I live up the hill on the outskirts of town and it can be 3-4 C colder than in town and also very cold winds, so I like to keep my babies tucked up nice....lol
Perennials that you grow from seed this year I think will need some protection, you could wait until v early spring and sow them then, they may not flower 1st year (depends on plants), but will be fully hardy by that winter.