How flowers get their colours

Have you ever wondered how flowers get their colours – why roses are red and violets are blue? Science and evolution play a vital yet fascinating role in creating each flower’s unique colours, which help plant species survive.

How flowers get their colours

Pigments determine a flower’s colour

DNA is responsible for each flower’s unique colour. Each plant’s genes direct cells to produce pigments of various colours (BMC Plant Biology, 2024). Genetic factors explaining anthocyanin pigmentation differences

These pigments are molecules that selectively absorb or reflect specific wavelengths of light. The colour we see is the wavelength it reflects (Frontiers in Ecology and Evolution, 2021). Major Flower Pigments Originate Different Colour Signals to Pollinators

For instance, when a flower is red, the cells in the flower’s petals absorb all wavelengths of light except the one that produces the colour red.

There are many plant pigments, but they’re primarily categorised into four different types. The most common plant pigment is chlorophyll which gives plants their green colour and plays a key role in photosynthesis (Optics & Laser Technology, 2011). Plants and colour: Flowers and pollination

However, you won’t usually find the chlorophyll pigment in flowers but instead in the plant’s leaves and stems.

The second plant pigment category is carotenoids, which reflect yellow, orange, and red. This pigment is what gives sunflowers their cheery yellow colour and marigolds their rich orange hues (Scientific American). Springtime Science: Exploring the Pigments in Flowers

Anthocyanins are the vibrant coloured molecules that are the source of reds, purples, blues, and pinks. These pigments belong to a class of compounds called flavonoids, which constitute one of the largest groups of plant pigments (BMC Plant Biology, 2024). Genetic factors explaining anthocyanin pigmentation differences

Scientists have identified thousands of flavonoids that are responsible for producing a range of colours in plants.

Anthocyanins give lilacs their soft purple hues and produce orchids’ vivid pinks.

The last main pigment category is betalains, a group of red and yellow pigments derived from the amino acid tyrosine and found in plants of the order Caryophyllales (Plant Physiology / botanical literature). Betalain pigment overview

Betalains replace anthocyanins in this order, which gives plants like beets and carnations their reddish-purple shade.

What about flowers with multiple colours?

Similar to the way painters mix paint colours to create a unique shade, the colours of flowers are determined by the composition and spatial distribution of pigments, which creates different gradients and patterns within the flower (University of Cambridge plant science research). The Diversity of Flower Colour: How and Why?

Interestingly, because pigments are chemicals, simple changes in environmental conditions including pH, metal ions and temperature can alter their colour composition (University of Cambridge plant science research). The Diversity of Flower Colour: How and Why?

For example, roses and blue cornflowers contain similar anthocyanin pigments, yet the blue colour in some flowers results from complexes formed between pigments and metal ions such as magnesium, iron and calcium.

Colours play a role in evolutionary survival

The colours of flowers serve far more significant purposes than for human enjoyment. The survival of each species depends on the colours of its flowers.

Flowers are the reproductive parts of plants. They attract pollinators by offering nectar and protein through their flowers.

When pollinators land on each flower, they pick up pollen and transfer it to other flowers they visit, allowing the plant to reproduce.

As most pollinators fly, the colours of a flower must attract them. Flower colours act as visual signals that help pollinators locate flowers and influence plant reproduction (Frontiers in Ecology and Evolution, 2021). Major Flower Pigments Originate Different Colour Signals to Pollinators

That’s why most flowers are brightly coloured.

Some flowers also produce pigments that can only be seen in the ultraviolet part of the light spectrum, which many pollinators — especially bees — can detect (Optics & Laser Technology, 2011). Plants and colour: Flowers and pollination