The smell in flowers comes form the special oils that are produced in the petals, as the plant grows. When this oil evaporates, which it does very easily, it gives off a fragrance which we can smell. Various combinations of chemicals in the oil of different flowers result in a variety of fragrances. Some are pleasant sweet smells, like those of roses, lilacs, and lilies, while others are quite unpleasant. The pelican flower of South America, for example, smells like rotten meat!
Flowers get their red, puple, orange, pink, or yellow colour from the pigments, or colouring matter, in the sap of their cells/ It is both the scent and the colours which attract insert and birds, who land on flowers to sip their nectar. In doing so, they help to spead the pollen from flower to flower. Many flowers have the same oil in their leaves, roots, and fruit as they have in their petals, so we can smell the fragrance in those places too!