Many plants aggregate small flowers into large, showy flowerheads with numerous petals to exploit their combined attraction to pollinators. But plants with individual blooms tend to produce just enough petals to lure visitors.

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So large numbers of petals are uncommon, except in flowers that have undergone mutations that trigger the development of abnormal ‘double flowers’, where very large numbers of petals are sometimes produced. Examples include double-flowered meadow buttercups, known as bachelor’s buttons, and double-flowered lesser celandine and marsh marigold, which are often sold in garden centres.

These mutants arise because all floral organs evolved from whorls of ancestral, leaf-like structures, and their development is controlled by a group of interacting genes that determine whether they will become petals, stamens or ovaries. But a mutation in these genes can cause all of the stamens to develop as petals, producing a sterile flower composed almost entirely of nothing else. The effect is most spectacular in blooms that have numerous stamens.

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Main image: Getty

Authors

Phil Gates taught biology at Durham University and writes for The Guardian’s Country Diary column.

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