Flowers are the reproductive structures of flowering plants, or angiosperms, and they employ a variety of colors to attract the animals necessary for their survival. The vast majority of species produce petals in vibrant shades of red, blue, yellow, or white to stand out against the surrounding foliage. This visual competition for the attention of pollinators means that green, the color of the leaf canopy, is a relatively uncommon choice for a flower’s showiest parts. Species that display green blooms have adopted a unique biological strategy, often involving the retention of a familiar pigment that most flowers intentionally discard.
The Chemistry of Green Coloration
The green color in a flower is a direct result of the presence of chlorophyll, the same pigment that gives leaves their color. In most brightly colored flowers, the genes responsible for chlorophyll production are switched off as the petal develops, allowing other pigments to dominate. Green flowers retain functional chlorophyll in their petals or sepals, reflecting the green wavelengths of light that the pigment does not absorb.
This mechanism differs from the way other flower colors are produced, which rely on different classes of compounds. Reds, purples, and blues are usually created by anthocyanins, while yellows, oranges, and some reds come from carotenoids. Green coloration is less about synthesizing a new pigment and more about simply not eliminating the plant’s default green compound during development. The final hue is a balance, where the chlorophyll is not masked by an abundance of these other pigments.
Biological Function and Pollination Strategy
The presence of green coloration in a flower signals an alternative evolutionary strategy to attracting generalist animal pollinators. Brightly colored flowers use their visual display to advertise a reward to insects and birds that see color well. By contrast, a green flower often utilizes the color for camouflage, either to hide from herbivores that might consume the delicate reproductive parts or because it does not rely on visual cues for reproduction.
Many green flowers are pollinated abiotically, meaning they rely on environmental forces like wind rather than animals. Wind-pollinated species do not need to invest the metabolic energy required to produce large, colorful petals or sweet nectar rewards, making the inconspicuous green color advantageous.
Even when green flowers are pollinated by animals, they tend to attract a specialized group of insects that do not rely on a bright visual signal. These plants often compensate for their lack of color with strong, sometimes musky, scents or by providing large amounts of pollen. Specific groups like flies and beetles, which may not perceive color as strongly as bees or butterflies, are frequently the targeted pollinators for these green blooms.
Common Examples of Green Flowers
One well-known example of a green flower is the Hellebore, often referred to as the Christmas Rose or Lenten Rose, which features a prominent green shade in many of its species. In Hellebores, the showy parts that appear to be petals are actually the plant’s sepals, which are the outermost whorls of the flower. These sepals remain green and prominent long after the tiny true petals have faded.
The Bells of Ireland is another familiar green flower, where the vibrant, cup-shaped structures are the plant’s calyxes, effectively forming a green lantern around the tiny, relatively hidden white flower inside. Certain varieties of orchids, such as the Cymbidium orchid, also produce striking green blooms, where the petals themselves are pigmented green. The Zinnia cultivar ‘Envy’ and some green-tinged varieties of Chrysanthemum further illustrate how this unusual color has been selectively cultivated for its unique aesthetic.