What is Far Red Light?
On the visible light spectrum, far-red light comes just before infra-red. Set at the extreme red end of the spectrum, far-red is defined as the spectrum region between 700 and 850nm wavelength. This wavelength is just barely visible to human eyes.
How Does Far Red Light Affect Plants?
To put it in the simplest terms, plants perceive far red light as shade. When they “see” more far red light than red light, they think they are being deprived of sun. For young plants in the germination and vegetation stages, this can be a huge problem. Seedlings may not grow at all under the influence of far red light, and developing plants are likely to stretch as they try to get out of the “shade.” However, carefully regulated blasts of far red light during the flowering phase can encourage higher yields, as plants have reached maturity and now interpret “shade” to mean that winter is on the way, their cycle is coming to a close, and they need to reproduce quickly before they lose their chance.