Why are autumn colours so varied? A Scottish perspective.

As autumn arrives in Scotland, the landscape transforms into a patchwork of fiery reds, sunny yellows, and rich oranges. But why does this colourful display occur? The varied autumn colours are closely linked to the unique ecology of Scotland. Let’s take a look at Scotland’s biggest players when it comes to trees and shrubs, and find out what they get up to when autumn arrives.

The Rowan tree

In the Scottish Highlands, one of the most vibrant trees turning colour is the rowan. Rowan trees produce clusters of red berries in late summer, which provide an important food source for birds and small mammals preparing for winter. The leaves of the rowan also turn a brilliant red-orange in autumn - and are one of the most distinctive trees at this time.

This striking foliage signals that nutrients are being withdrawn from the leaves back into the branches and roots of the tree. As chlorophyll - the green pigment responsible for photosynthesis - breaks down, other pigments called anthocyanins are revealed. These red and purple pigments act as a 'sunscreen' to protect the leaves from damage as they shut down for winter.

The Scots pine

Unlike deciduous trees that shed their leaves in the autumn, Scots pines are evergreen conifers, meaning they retain their needles throughout the year, including in autumn. This evergreen characteristic provides a year-round green backdrop to the colourful foliage of deciduous trees and shrubs, creating a stunning contrast in the landscape.

This is the time of year when Scots pine trees typically mature and release their pine cones. These cones can vary in colour, from green to brown, and often contain seeds within. The cones are a vital part of the tree's reproduction process, and in the autumn, they start to disperse their seeds to ensure the tree's future growth.

Heather

Scotland is home to beautiful swathes of heather moorlands. Heather plants explode into flowers from July to September, coating the hills and fields in pinkish-purple blooms. As the weather cools, the heather transitions to orange and coppery-red hues. This marks the end of the heather's growing season. The dramatic seasonal shifts in heather moorlands provide essential habitats for wildlife including red grouse, mountain hares, and butterflies.

Deciduous trees

In woodlands across Scotland, deciduous trees like oak and beech also paint the landscape in warm autumn tones. The cycle begins when the length of daylight and temperatures drop. Trees restrict their water transportation systems, allowing vital nutrients to be sealed off in the roots. Chlorophyll breaks down, the green fades, and yellow xanthophylls and orange carotenoids from the leaves are revealed. Leaves are eventually shed to reduce water loss over winter. But not before delighting us with their autumnal splendour.

A varied landscape

The varied yellows, oranges and reds across Scotland can be observed in individual tree species tailored to survive in this climate. Conifers like Scots pine keep their needles all year long due to waxy coatings. Deciduous species like oak and rowan withdraw nutrients and pigments during fall in preparation for leaf drop. Heathlands burst into purple flowers in late summer before shifting to coppery winter hues. So as you explore the Scottish countryside this season, appreciate how plants and trees have adapted through evolution to thrive in these landscapes. Their vibrant autumn cloaks are a beautiful visual reminder of natural selection in action.