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How do double-flowered chrysanthemums and dahlias develop?

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Sunflower — 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.

Double-flowered chrysanthemums and dahlias develop through a natural mutation in species that typically possess radiate heads. In a standard radiate head, the inflorescence consists of central disk flowers surrounded by marginal ray flowers.

In double-flowered forms, a mutation causes most or all of the disk flowers to be transformed into ray flowers. While these modified flower heads would struggle to survive in the wild, they are highly valued in horticulture for their showy appearance and are actively perpetuated by cultivators. Consequently, while "daisy-flowered" varieties maintain the normal radiate structure, the more common garden types of chrysanthemums and dahlias are those that have undergone this transformation to become double-flowered.1