How do trees grow and change through the seasons?

Sunlight through misty trees in an ancient wood
Trees go through quite the journey to become so big and lovely! (Photo: Helen Dixon/Alamy Stock Photo)

Trees go through lots of complicated changes and actions the whole year round. They may look peaceful and still, but they're busy at work for most of the year growing and developing. Along the way, they purify our air, provide homes for wildlife and make out landscapes beautiful. They're pretty amazing!

How do trees grow?

Trees make their own food through photosynthesis, where leaves work as little food factories for the tree. Leaves contain a green pigment called chlorophyll. In spring and summer, they soak up sunlight and this combines with the chlorophyll, water and carbon dioxide from the air to make sugars.

These sugars give the tree the energy to grow new twigs and branches. As they do this, trees also lock up the carbon and release oxygen so help us breathe.

Scots pine bark close up
(Photo: Laurie Cambell/WTML)

The trunk gets bigger too. The bark on the outside is made of dead cells, but inside is a living layer of cells called the vascular cambium. These cells form vertical channels, a bit like tubes, called xylem and phyloem. They xylem carries water and nutrients from the soil up to the tree for it to grow. The phyloem carries the sugars from photosynthesis down to the roots for energy.

Each year, the vascular cambium creates new cells. These push the bark outwards and make the trunk fatter. You can see these growth rings when a tree is cut down. The thickness of each ring depends on how fast the tree was growing that year, usually depending on the weather. You can even use these rings to see how old a tree is and if it was attacked by pests and diseases.

How do trees change throughout the seasons?

Deciduous trees (trees that lose their leaves) go through a distinct yearly cycle.

Spring: Leaf buds appear and trees produce flowers. Flowers help attract insects for pollination so the tree can be fertilised and produce seeds later in the year. Our blossom and catkin ID will help you spot tree flowers.

Summer: Trees are covered with green leaves and are busy making food to grow through photosynthesis. 

Autumn: Trees start to produce less chlorophyll  because there is less sunlight, so other colours in the leaves begin to show through. The leaves change to bright reds, yellows and browns before drying out and falling off. Find out more about how leaves change colour.
Trees also produce seeds at this time of year – sometimes contained in fruits and berries. Seeds eventually fall on the ground, or are carried away by animals or the wind, and some grow into new trees.

Don't forget to check out our fruits and seeds spotter sheet when autumn comes around.

Germinating common oak acorn
Seeds can take a while to germinate after falling, some need very special conditions. (Photo: FLPA/Alamy Stock Photo)

Winter: Trees become dormant, which is a bit like going to sleep. growth stops and the branches are bare. They do this to conserve energy and rest up before the cycle begins again – it helps keep trees healthy.

Become a super spotter and help scientists track trees

Sign up to our Nature's Calendar site and help us keep track of natural events like changes in trees throughout the year. You can log your first sightings of things like leaf buds, blossom and seeds. Scientists can then use these records to find out more about how climate change is affecting nature and the seasons.

Do you have a favourite tree?

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