The Science of Plant Colors

Why are plants different colors?

We have been shown the importance of color from the artistic point of view, your garden as a masterpiece, colorful and pretty. But what do those colors mean? Why do plants have color and what causes plants to be different colors? Almost everyone has heard of chlorophyll, but have you heard of the other two type of plant pigment? Do you know what their functions are?

It is not exactly simple, and most gardeners might not even care. However, I think it would be safe to make the assumption that for just about every person who sees their garden as a medium for artistic expression there is another who could only describe a flower in terms of its morphology and functional benefits for the particular plant. From my experiences here at Wayside Gardens, I can also promise you that neither will do so with more or less passion.

American kids officially learn about chlorophyll in seventh grade life science, though they may be introduced to it a little earlier. So we’ve all heard of it. We know what photosynthesis is- the method by which plants turn light into usable energy. Plants store this energy, animals eat the plants, animals eat animals that ate the plants, and humans eat plants and animals. Ultimately, almost all energy for growth and movement on Earth comes from the Sun via photosynthesis. Yay! Everyone give a round of applause to plants for shouldering such a huge responsibility for the rest of us.

Chlorophyll is the pigment responsible for absorbing most of the light during photosynthesis. There are two different kinds: a, green to blue-green and b, red. Chlorophyll a is the most common. Thus, most leaves are usually green. You’ll notice, in the summer that trees are completely covered with leaves because this is when they are doing the bulk of their growth.

Carotenoids are the pigment that give plants, carrots for example, colors ranging from yellow to orange. They have many functions in nature, and though they are important to many animals, they cannot be synthesized and must be ingested. In plants they also have functions in photosynthesis. During Autumn, the leaves of deciduous trees change color because they no longer need to collect sunlight and the green chlorophyll thins out revealing the colors of the carotenoids and another reddish chlorophyll before the leaves fall.

Flavonoids are the third kind of pigment and provide the largest variety of color to flowers, ranging from red to blue. When combined with the first two, the overall combination determines the look of a particular plant.