Why do flowers smell?

Flowers have just one biological role: to guarantee pollination. Many showy blooms are pollinated by insects, attracted by a flower’s bright colours and the reward of energy-rich pollen or nectar. But flowers must also lure insects from farther afield – enter, scent.

The aroma of some flowers contains up to 100 different chemicals. These are modified from chemicals in leaves which deter grazing animals, but are manufactured within the flower. Warm weather stimulates their release – just when bugs are most active. Characteristic scents encourage insects to visit other flowers of the same species and so transfer pollen between them. The blooms of evening primrose and night-scented stock release their sweet aroma in the evening, attracting nocturnal moths. These moths only visit other night-scented flowers, thus reducing pollen wastage. Some species have ‘stinky’ flowers, which only attract carrion-seeking insects. The clove scent of one Bulbophyllum orchid is so particular that it lures just one species of fly, thus ensuring efficient pollen transfer.

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