Unopened flower buds of coreopsis are boxy looking, very distinctive.

Flowers of yellow cosmos and coreopsis are hard for me to tell apart
from a photo.

I thought cosmos were going to be a great iris companion plant, drought
tolerant, airy foliage, self sowing. Several generations later, self
sowing in the iris patch, they grow up to 6 ft tall with dense foliage.
Beautiful in bloom, but too enthusiastic! smothering irises. First
generation was <3 ft.

Linda Mann east TN USA zone 7