The calyx of a flower is the group of leaf-like or petal-like structures arranged at the base of the flower or the top of the stalk. The calyx is often, but not always, green. In some plants, the calyx is the same color as the true petals.
The calyx is made up of individual structures called sepals. Sepals may be separated from one another or fused into a single ring. The sepals protect the rest of the flower, especially when the flower is still just a bud. Most sepals are smaller and less showy than the structures they directly protect, the petals of the corolla. In plants such as the iris, the corolla and the calyx look roughly the same and are not readily distinguished. Sepals that are just as big and colorful as petals are called petaloids.