The most readily recognisable characteristics of Eucalyptus species are the distinctive flowers and fruit (capsules or "gumnuts").
Flowers have numerous fluffy stamens which may be white, cream, yellow, pink or red;
in bud, the stamens are enclosed in a cap known as an operculum
which is composed of the fused sepals or petals or both.
Thus flowers have no petals, but instead decorate themselves with the many showy stamens.
As the stamens expand, the operculum is forced off, splitting away from the cup-like base of the flower;
this is one of the features that unites the genus.