Flower head of the Costus comosus, Red Tower Ginger, National Botanical Garden, Lawai, Kaua'i. The bright red "petals" are actually bracts, modified or specialized leaves associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often (but not always) different from foliage leaves, for example being smaller, larger, or of a different color or texture. The true flowers are small yellow blossoms like those in this shot.
