Doubled petals

"Double-flowered" describes varieties of flowers with extra petals, often containing flowers within flowers. The double-flowered trait is often noted alongside the scientific name with the abbreviation fl. pl. (flore pleno, a Latin ablative form meaning "with full flower"). The first abnormality to be documented in flowers, double flowers are popular varieties of many commercial flower types, including roses, camellias and carnations. In some double-flowered varieties all of the reproductive organs are converted to petals — as a result, they are sexually sterile and must be propagated through cuttings. Many double-flowered plants have little wildlife value as access to the nectaries is typically blocked by the mutation.

Double flowers are the earliest documented form of floral abnormality, first recognized more than two thousand years ago.Theophrastus mentioned double roses in his Enquiry into Plants, written before 286BC. Pliny also described double roses in 1st century BC. In China, double peonies were known and selected by around 750AD, and around 1000AD double varieties of roses were cultivated to form the China rose (one of the ancestors of modern hybrid tea roses). Today, most cultivated rose varieties bear this double-flower trait.

Herbalists of the Renaissance recognized double flowers and began to cultivate them in their gardens — Rembert Dodoens published a description of double flowers in 1568, and John Gerard created illustrations of many double flowers beside their wild-type counterparts in 1597. A double-flowered variety of Marsh Marigold was discovered and cultivated in Austria in the late 16th century, becoming a valued garden plant.

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Wikipedia