More kinds of plants are crammed together in the tropical rainforests than anywhere else on Earth. The result is astonishing beauty and intense competition, a plant battleground.

Water plants create beautiful, bizarre worlds; flowers smother rivers and lakes; plants fight and hunt; a river bubbles like champagne as plants create the atmosphere itself.

Between the tropics and the frozen poles lies a region dominated by relentless change in the form of the four seasons: spring, summer, autumn and winter. Each one presents plants with huge challenges.

Desert plants spend decades in suspended animation waiting for rain, or they travel to find it. They survive using weapons, camouflage, and surprising alliances with animals.

Two in five wild plants are threatened with extinction, but people are finding new ways to help them, from projects in Africa to reseed the landscape, to the rebuilding of a tropical forest in Brazil, tree by tree.