A leaf contains a green substance called chlorophyll. This substance traps some of the energy in sunlight. The leaf uses the trapped energy to make food from carbon dioxide, water and minerals.

The main part of a flat leaf is called the blade. It may have a central midrib from which branch the veins. The midrib and veins bring water to the leaf and take away the food. The food is made in the rest of the leaf blade.

The shape of the leaf can vary greatly from one plant to another. For example many plants have small simple leaves like the oak, but some, like the ash, have such huge leaves that each leaf is divided into leaflets.

Leaves are adapted to help the plant survive in its habitat. For example many conifers can live in habitats where snow is common in winter. The conifer leaves are needle shaped and covered in wax. The shape only offers a small area for snow to settle on and the waxy surface makes the snow slide off. These features help the leaf remain exposed to sunlight after a fall of snow so the plant can keep making food. If the snow covered the leaves for a long time the tree would starve.

Perhaps the most unusual adaptation of a leaf is to feed on insects. This allows the plant to grow in habitats where there are few minerals in the soil. The plant gets the minerals it needs from the insects trapped by the leaves. Some plants which feed on insects such as the butterwort and sundew have sticky leaves which trap any insect that lands on them. The Venus fly trap has leaves which snap shut when insects land on them and the pitcher plant has a leaf made into a hollow tube. This contains water into which insects fall and drown.