Oenethera biennis buds

The buds of Oenothera biennis develop long, faintly hairy stalks that curve up before the flowers open. The stalks spread and curve down later, becoming redder. The about cylindrical buds are initially green, the outside surfaces of the sepals faintly hairy and turning red purple before they release the yellow corollas.

There is a leafy green bract, lance-shaped with pointed tip, below the pedicel of every flower (iNaturalist; Wikipedia).