THE BLUENESS OF ORCHIDS

Blue Orchid

Ophrys Speculum (Image: Hans Hillewaert)

Truly blue flowers are less frequent than those in other primary colors. When inventing blue orchids, nature created even less variety. Why is that?

The color of a flower or plant depends on heredity, environmental factors, and color perception.

Coloring is mostly predetermined on a cellular level. A plant’s potential genetic color palette consists of only four pigments:

  • Chlorophyll (green) creates the coloring of leaves and stems and is present in all plants.
  • Flavones (pale yellow; colors invisible to human eye) can be found in roses.
  • Carotenes (yellow; orange) ensure the coloring of sunflowers and marigolds.
  • Anthocyanidins (red; blue; purple) give geraniums, day lilies, violas, delphiniums and blue orchids their color. The bluest blue is created by delphinidin which does not exist in orchids. Blue pigmentation is rare in other flowers as well. Most blue flowers are closer to purple and lilac than they are to true blue.

Several pigments may be present within the same plant, creating unique shades of color.

The flowers of blue orchids from the same species may come in many different shades. A blue Cattleya could be lilac, rose blue, blue-lavender, lavender-blue, blue-violet, blue-purple or indigo blue – and anything in between!

Soil acidity and light exposure play a part in manifesting the blue color that has been genetically enabled. Blue orchids either grow on the ground (terrestrial), high up on trees (epiphytes) or on rocks or tree bases respectively (lithophytes).

According to orchid expert Robert J. Griesbach, PhD, ‘…the blue color in many orchid flowers is known to be associated with an alkaline floral pH. Research on some blue orchid forms has shown that blue color increases as the floral pH becomes more alkaline.’  A pH of 7 and higher is alkaline.

Depending on how much light and shade an orchid receives, coloring of its blooms may vary. Blue Vanda orchids, for example, originally are epiphytes, sometimes lithophytes, hence receive light that has – at least partly – been filtered through foliage. Exposing them to full sun light will produce purple-hued flowers rather than blue ones.

Hereditary blue color pigmentation being expressed with the help of ideal soil and light conditions, blue color is visible only when reflected by light. To identify a blue orchid as blue, the eye seeing it must be able to perceive its blue color. While the female human eye is capable of discerning a wider range of blues than that of a man, insects can see color pigments that are invisible to humans. Hence only beetles, bees and butterflies might know which white orchids are in reality blue.

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