Synopsis

Between the tropics and the frozen poles lies a region dominated by relentless change, in the form of the four seasons. Each offers plants brief opportunities and challenges, but to survive they must get their timing right. Sir David Attenborough kicks off the episode by showing of the most extreme examples of seasonal plant life in the Arctic Circle - Finland.

In spring, rising sap in Canada’s Maple trees fuels the growth of new leaves. Hungry Sap Sucker Woodpeckers hammer holes in the bark - wounds that leak pure maple syrup. The tree seals the holes and the bird drills more - it’s a life-and-death battle.

A different enemy awaits early growing nettles. The Dodder plant has no leaves, just a stem that smells for prey! It pierces its chosen victim and sucks out what it needs.

Summer means flowering - and heat. The South African Cape is coloured by millions of flowers, all competing for pollinators. A huge summer fire wipes the land clean, but it’s not a disaster for everything. A new shoot appears through the blackened earth - the Fire Lily, which hasn’t flowered since the last fire 15 years ago. It emerges into a world with no competitors at all.

Seeds need to spread before winter and they have many tricks. Parachutes to catch the wind, mimicry to trick animals, explosive mechanisms to fire seeds away.

In autumn, forest fungi are the fruiting bodies of a huge underground network that connects tree to tree - the woodwide web. Trees use it to communicate and to pass vital nutrients to relatives and others in need.

The approach of winter means rapid shutdown. Some that don’t get it right grow stunning ice-flowers. Looking like delicate sculptures, they emerge from stems that rupture in the first frosts.

Seasonal plants depend on the predictability of the seasons. Their lives are becoming ever harder with the disruptions by caused climate. Sir David Attenborough visits the ancient giants like Giant Sequoia Trees, in California, which are thousands of years old, are starting to suffer from the consequences of climate change