(botany) the whorl of petals of a flower that collectively form an inner floral envelope or layer of the perianth
"we cultivate the flower for its corolla"
An outermost-but-one whorl of a flower, composed of petals, when it is not the same in appearance as the outermost whorl (the calyx); it usually comprises the petal, which may be fused.
"The bee hovered near the bright blue corolla before diving down into the center to collect nectar."