What are ray flowers in the Asteraceae family?

In the Asteraceae family, ray flowers are specialized, strap-shaped florets that typically form the marginal rows of a flower head. While the center of a radiate head is composed of tubular disk flowers, the ray flowers extend outward, featuring a corolla that is tubular at the base but prolonged into a flat, petal-like projection called a ray or ligule.12

These structures are responsible for the "petals" seen on flowers like daisies or sunflowers. Ray flowers are generally either pistillate (female) or neutral, lacking a functional ovary. In some species, the entire head may consist only of ray flowers, or conversely, only of disk flowers.231

It is important to distinguish ray flowers from ligulate flowers; while both have strap-shaped corollas, ligulate flowers—found in the tribe Lactuceae—are bisexual and represent all five lobes of the corolla, whereas ray flowers are typically associated with the radiate heads of other tribes.2