What Are the Functions of Flower Bracts?
Many perennials we grow in our gardens have “insignificant inflorescence,” or tiny flowers that grow in a center surrounded by modified leaves called “bracts.” Often we grow a plant not for its flowers but for its bracts.
The primary task of a bract is to protect the inflorescence. Some, like the stinking passionflower, exude a substance that repels grazers. Others have bristles. They may look like a leaf, part of a flower or, like Euphorbia (spurge), part of the plant.
A large, often graceful bract known as a spathe surrounds or encloses a flower cluster, or spadix, in calla lilies, jack-in-the-pulpits and peace lilies.
Large or colorful bracts surround flowers to bring their attention to specific insects. Poinsettias and sunflowers have bracts that signal pollinators with bright colors or provocative (to bugs) shapes.
The stiff bracts on strawflowers and paper daisies are actually dead tissue reused to surround flowers. They often remain long after the seeds have dispersed and are used as dried flowers.
Bracts may imitate the sepals, or calyx, of a flower. In carnations and hibiscus, this adds strength to areas surrounding the ovule, the part of the flower where seeds develop.