Purple is an enchanting color that has long been associated with royalty, spirituality, and mystery. But is it actually rare in the natural world? Let’s take a closer look at the prevalence and sources of the color purple in nature.
What Makes the Color Purple?
The color purple is a mix of red and blue light. In physics, purple light has wavelengths between 380-450 nanometers. The human eye sees this mixture of wavelengths as the color purple.
In nature, the color purple comes from pigments. Pigments selectively absorb certain wavelengths of light and reflect others. For example, anthocyanin pigments in plants absorb green to yellow light and reflect back red and blue light. This selective absorption and reflection is what makes plant parts like flowers and fruits appear purple to our eyes.
How Rare is the Color Purple in Plants?
Purple is relatively uncommon in plants compared to other major plant pigment colors like green, red, yellow, and orange. However, it’s not exceptionally rare. Here are some estimates on the occurrence of purple in plants:
- About 10% of flowering plant species have purple flowers
- Around 6% of fruits and vegetables have purple skin or flesh
- Less than 1% of leafy greens and herbs are purple
So while not nearly as common as red or yellow, purple is prevalent enough in about 1 in 10 flowering species. Some common examples of purple produce include purple cauliflower, purple carrots, purple potatoes, purple asparagus, purple cabbage, purple beans, and eggplant.
| Category | Percentage purple |
|---|---|
| Flowering plants | 10% |
| Fruits and vegetables | 6% |
| Leafy greens and herbs | Less than 1% |
Why Aren’t More Plants Purple?
If purple confers no selective advantage, it is likely to remain relatively rare. There are a few explanations for why purple is an infrequent color in nature compared to other major plant pigments:
- Purple anthocyanin pigments are energetically expensive for plants to produce.
- Purple coloration provides little benefit in photosynthesis.
- Purple leaves absorb less light and make less food via photosynthesis.
- Purple plants are not better pollinated or dispersed than green plants.
- Purple color is not associated with any major defensive compound, unlike red’s link with antioxidants.
With no major adaptive benefits, there has not been strong selective pressure for purple pigmentation in plants through evolution. Occasional mutations cause purple coloration, but without an evolutionary advantage these remain relatively rare.
A Few Vibrantly Purple Plant Families
While globally uncommon, vivid purple flowers and foliage are very characteristic of certain plant groups where purple pigmentation has become common through evolution. Some notably purple plant families include:
- Orchids – Many strikingly purple orchid flowers. Examples include phalaenopsis, cymbidium, and cattleya orchids.
- Irises – Purple and blue irises are among the most popular garden flowers.
- Sages – Purple sage and its cultivars feature strongly purple foliage.
- Basils – Purple basil varieties used for both ornamental and culinary purposes.
- Coleus – Prized for its vividly colorful foliage, including many purple varieties.
- Violas and Pansies – Abundant purple coloration in these edible flowers.
- Eggplants – Purple skin and flesh is characteristic of wild and domesticated eggplant.
Through selective breeding or natural selection, vivid purple has become very common in these plant groups. But on the whole across the plant kingdom, purple ranks behind several other major pigment colors in prevalence.
How Common is Purple in Animals?
Beyond the plant world, purple is also fairly rare in the animal kingdom. Unlike plants, animals cannot synthesize their own purple pigments but must acquire them from their diet. As a result, truly purple animals are uncommon. Here is how purple rates among major animal groups:
- Less than 1% of vertebrate species have purple coloration.
- About 5% of insects exhibit a purple hue.
- Roughly 10% of cephalopods like octopus and squid can change their skin to purple for camouflage.
- A few percent of ascidians, marine chordates, are vividly purple.
While occasionally seen in insects, aquatic life, and elsewhere, animals with natural vibrant purple coloration are quite rare compared to red, orange, yellow, green, blue, and brown animals. Entire classes of organisms like mammals and birds almost never exhibit true purple coloration.
| Animal Group | Percentage purple |
|---|---|
| Vertebrates | Less than 1% |
| Insects | About 5% |
| Cephalopods | 10% |
| Ascidians | A few % |
A Few Vividly Purple Animals
A handful of vividly purple animals stand out as exceptions to the general rarity of purple in nature:
- Purple Frogfish – This freaky fish from tropical oceans can be purple, blue, or pink.
- Violet-backed Starling – This African bird sports iridescent purple feathers.
- Purple Sea Urchin – The strikingly purple test of this urchin acts as camouflage.
- Violet Sabrewing Hummingbird – Native to Central America, these hummers have unmistakable purple feathers.
- Purple Emperor Butterfly – One of the few butterflies to feature vivid purple wings.
While these examples demonstrate purple can occasionally occur in animals, it is far from a common color in any major animal group.
What are the Rarest Colors in Nature?
Compared to the major pigment colors like red, blue, yellow and green, purple is relatively rare across the plant and animal kingdoms. But it is not the absolute rarest color found in nature. Here are a few of the rarest natural colors:
- Piezochromic Color – Vibrant blue color displayed by some minerals like iolite when compressed.
- Aposematic Pink – Bright pink found only in a few poisonous insect species as warning coloration.
- Shiny Orange – Sported by a single species of Costa Rican shrimp to mimic poisonous nudibranchs.
- Iridescent Olive – An extremely rare iridescent hue found in certain beetle species.
While limited data makes it difficult to definitively rank nature’s rarest colors, most experts agree purple is relatively uncommon but far from the rarest pigment found across plants and animals.
Conclusion
Purple is an alluring color that captures the imagination. But based on current data, purple is not exceptionally rare in the natural world compared to other major pigment colors. Purple ranks behind colors like green, yellow, red, and blue in prevalence across plants and animals. However, vivid purple coloration does stand out as highly unusual when it occurs in particular organisms. So while not the rarest, purple is still a relatively uncommon and often striking natural color.
