Eucalyptus flowers have no petals, but instead decorate themselves with the many showy stamens and they are enclosed in a cap known as an operculum.

This is an Eucalyptus flower blooming.

https://video.nostr.build/ae72422b1e06cf380e8f4683b6882b16454a8eed72821c3b06bc5aabd8e64b2d.mp4