The tropical rainforest grows close to the equator. Here the rainforest very hot all through the year and rain that falls almost every day. The heat and water provide ideal conditions for rapid plant growth, and the forests are packed with many different kinds of plant. For example, in the Amazon rainforest there are over four thousand different kinds of trees.

Although the heat and water can help the plant grow quickly the soil is not rich in minerals. The reason for this is due to the age of the rainforests. They have existed for millions of years and during this time the water has dissolved the minerals in the soil and carried it away into streams and rivers and eventually into the sea. Even so, huge amounts of minerals are locked up in the bodies of the rainforest plants. They help to keep the plants alive. When a plant dies it falls to the forest floor and quickly rots in the heat and damp and its minerals are released. Rainforest trees have a huge network of shallow roots which grow through the soil and collect the minerals as they are washed from the rotting plants into the soil. This means that very small amounts of minerals leave the rainforest and most of the minerals are quickly recycled.

Many rainforest trees grow to height of between twenty and thirty metres. They have very long smooth trunks which only form branches near the top. The branches spread out from almost the same place and look like the spokes in an umbrella. The arrangement of branches is called a crown and the trees grow so closely together that their crowns almost touch and form a roof over the forest called a canopy. This is the leafiest part of the forest and is the place where most of the food is made.

The leafy canopy stops a large amount of light from passing through it and the region below is shady. Some plants are adapted to live in the shade and form smaller trees and bushes. In some parts of the rainforest there can be so many plants that it takes raindrops up to ten minutes to drip through the leaves from the canopy to the forest floor.

Some plants avoid the darkness below the canopy by being adapted to living on branches high in the trees. Mosses coat the branches and larger plants have roots which grow into the moss to hold them in place. Branch-living plants cannot get their water from the soil. They may soak it up from the damp air or have leaves which form cups in which the rainwater can collect. Examples of these are the bromeliads.

The strong trunks of the rainforest trees provide support for plants with weaker stems. These plants are climbers. The best known climbers are the climbing vines whose dangling stems are called lianas. They grow through the canopy and tie the crowns together. This helps to support the trees when they are blown strongly by the wind in a tropical storm.