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Which Asteraceae plants have flower heads made entirely of disk flowers?
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Asteraceae
The flowering head of a sunflower (Helianthus annuus) is formed of yellow, petal-like ray flowers and a brown center of minute disk flowers.
In the Asteraceae family, flower heads that are composed entirely of disk flowers are referred to as discoid heads. These heads consist of flowers with regular, tubular corollas, typically featuring four or five apical teeth.1
Common examples of Asteraceae species that possess these discoid heads include:
In these plants, the flowers within the head are generally perfect (bisexual) and fertile. While other types of heads exist in the family—such as radiate, disciform, and ligulate heads—the discoid type is specifically defined by the presence of these tubular disk flowers without the marginal ray flowers found in radiate types.12