Cannabis grows and develops differently to different spectral colors. One of the most critical factors in cannabis cultivation is light, but light has different colors, which specific wavelengths of light can be used to obtain satisfactory cannabis? According to the current research, the main role is the following.
UV:
The effects of UV light on cannabinoids were first presented in an academic paper by Lydon et al. 1987. Lydon and his team concluded that UVB increased floral THC concentrations.
UVB has strong radiation and can easily cause damage to plants and growers. But UV light works by stressing the plant, which defends and produces more THC. Therefore, relatively mild UVA can have the same effect. Even UVA needs to control the amount of use, that is, the lighting time, to avoid damage caused by prolonged exposure.
Blue light:
Studies have shown that blue light also has a positive effect on the increase in THC concentration. Blue light has been shown to increase the concentration of cannabinoids, especially THC, as demonstrated in the article by Magagnini et al. 2018. This is the first article to compare the differences between LEDs and HPS in cannabis growth and flower quality.
At the same time, blue light will also enhance the compactness of the plant and make the plant denser, preventing the plant from being too long to support large flowers. This is also why traditionally, people like to use MH lamps during the growth phase of cannabis because of the strong blue light in its spectrum.
Green light:
Green can effectively penetrate the leaf layer. In contrast, red and blue light are almost completely absorbed by the first leaf layer. Therefore, the lower leaf layers can utilize green light in photosynthesis and also produce yield as well.
Appropriately adding green light to the plant lamp makes the color of the lamp look more normal, which is beneficial for the grower to observe the plants during the planting process and find out diseases, insect pests or other problems in time.
Red light(deep red 660nm):
As we all know, the utilization efficiency of red in photosynthesis is very high.
For cannabis, it is more important to control the ratio of red to far-red, which has important effects on plant morphology and even flowering and germination.
Cannabis plants become taller under low R:FR ratio conditions (Magagnini et al., 2018). This can be detected very early by stem and petiole elongation (Figure 3). Elongated plants that do not receive enough red light are weaker relative to far-red light and therefore cannot carry high yields.
Far red light:
American cannabis cultivation expert DR rugbee has demonstrated the importance of far red for plants and cannabis. Far red plays an important role in plant morphology and flowering. The key is to control the amount used and when. Too much far red will cause the plant to grow too long during the growing stage, resulting in no large flowers. The addition of far red in the flowering stage and the use of end-of-day treatments can speed up flowering and improve yield.
Spectra rich in far red are more suitable for mother plant cultivation for longer cuttings because of the ability of far red to make plants grow longer.
How to choose the best spectrum for cannabis cultivation?
Is it not important except for the wavelengths of light mentioned above? In fact, it is not. Many studies have also shown that although other light is not as efficient as the light mentioned above, it has a synergistic effect and improves the overall photosynthetic efficiency.
So it's wise to choose a spectrum that includes all wavelengths from UV to far-red, but keep in mind that well-balanced ratios give the best growth results.
On the other hand, the optimal ratio varies according to different cannabis varieties and growth stages.
Is there an easy way to control the Grow Lights to achieve the best spectrum?
Adjustable spectral light intensity + smart plant lights that automatically execute lighting strategies are the best choice.
