cornflowers

Plant them in the open ground, they will grow to approx 18 inches.

there is a dwarf one that grows 10" but usually as mg says about 18". they prefer a sunny site but will manage in light shade.

Yes, I agree an open site as cornflowers were originally meadow flowers.

There seems no reason why you shouldn't grow cornflowers in a pot if you want to, if that's how much you like cornflowers, though normally one would sow them into a flower bed or some open ground. Actually, you may find they look best when there is a drift of them, or when they are combined with a suitable companion plant, particularly certain other arable wildflowers. Bluer than a baby's eyes. Easy to grow. Have fun.