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Flowers are the defining feature of angiosperms, the vast majority of plant species. They serve as the reproductive organs that develop into fruit. A flower can be perfect (hermaphroditic) with both male and female parts, or imperfect (unisexual) with only one. Plants bearing both male and female flowers are monoecious; those bearing only one sex are dioecious.

Evolution has shaped flowers to be bright and colorful so that they attract pollinators—birds, butterflies, bees, and wasps—ensuring successful fertilisation.

Parts of a flower

Despite the diversity of shapes and sizes, a flower’s anatomy is largely consistent: sepals, petals, stamens, and carpels. These elements are arranged in concentric whorls. A flower that contains all four parts is called complete; one missing one or more is incomplete.

Sepals

Sepals are green, leaf‑like structures that encase the flower bud, protecting it during development. Together, they form the outer whorl, the calyx. While most sepals are green, some species display coloured sepals, or the sepals are modified into bracts—leaf‑like structures that can be larger and more conspicuous than petals. When petals are absent, brightly coloured bracts often perform the role of attracting pollinators.

Petals

Petals are typically the most striking part of a flower, often vivid in colour and occasionally scented. Their primary role is to lure pollinators and safeguard the inner reproductive structures. The whorl of petals is called the corolla, and together with the calyx they form the perianth.

Stamens

The stamen is the male reproductive unit, forming the inner third whorl, the androecium. Each stamen consists of a filament topped by an anther, where pollen grains are produced. A pollen grain contains a vegetative cell that forms the pollen tube and a generative cell that delivers the sperm. When a pollinator visits a flower, pollen adheres to it and is transferred to the stigma of another flower.

Carpels

Carpels are the female parts, making up the innermost whorl, the gynoecium. Each carpel has an ovary that houses ovules. The ovary extends into a style ending in a sticky stigma, which captures pollen. After pollination, the pollen tube grows through the style to fertilise the ovules. Fertilised ovules develop into seeds, while the ovary matures into fruit.