Rainbows are formed when natural sunlight is refracted through moisture that is suspended in the atmosphere, with that refraction breaking the natural sunlight into its individual visible light components that comprise the color lighting spectrum. However horticulturists have come to understand that these varying intricacies within the spectrum of light have varying effects on the plants soaking up all that UV light for sustenance and growth.
Color Spectrum and Plant Growth
Green plants need natural sunlight to activate the chlorophyll that generates nutrients in the plants’ vegetation through the process of photosynthesis. Over millions of years of growth and development, the biochemistry in leaves has evolved to use different parts of the color spectrum for different purposes. It is not necessary to deconstruct natural sunlight in order to make plants grow, but when plants are cultivated in an indoor growing facility that does not use natural sunlight, a cultivator will generate better quality crops with larger yields by matching the color spectrum of a facility’s artificial LED grow lighting system with the specific color spectrum needs of the plants.
As is observed with a rainbow, the visible color spectrum of light ranges from red and orange tones, to deeper blue and violet tones. This spectrum is measured as electromagnetic radiation with wavelengths between approximately 450 and 700 nanometers (nm). Some species of plants have also adapted themselves to use light that is slightly outside of the visible range and in the infrared and ultraviolet electromagnetic radiation bands, but those are not generally cultivated en mass.
Optimizing the Color Spectrum of Light for Horticulture
Botanists have gained a solid understanding of how plants use different color spectrum components during their growth cycles, with the following generalizations holding true in large part across most plants:
Blue light is essential during a plant’s germination phase. Stronger concentrations of blue light will encourage sprouting and development of strong roots.
Violet or purple light has a shorter wavelength and higher energy, and is thought to be effective as a secondary light source to facilitate growth and development of a plant’s leafy vegetation.
Green light is generally reflected away from plants (which is why they appear green), but plants will absorb a small amount of green light throughout the photosynthesis process.
Yellow and white light have the lowest effect on plant growth.
Red light impacts plant growth in several ways, including during the blooming and flowering phase. Certain specific red wavelengths will increase the production of a hormone in a plant’s vegetation that prevents the breakdown of chlorophyll. With more chlorophyll, a plant generates more nutrients and grows taller with more leafy vegetation.