1. Vegetative Stage – “Blue” light for healthy leaves (range: 400-500nm; ideal: 460nm)
During the vegetative stage it is recommended to aim for as many leaves as possible, and to make sure plants stay rather compact, don’t stretch too much, and develop strong stems. Indoor growers tend to use metal halide bulbs, compact fluorescent lamps (CFL’s), or T5/T8 lighting fixtures with a blue band of light for the first few weeks to achieve these goals. When cannabis grows in nature, the high angle of the sun in spring and summer allows more “blue” wave lengths to penetrate through the atmosphere, a signal for cannabis plants to grow strong, large and healthy leaves.
2. Flowering Period – “Red” light for giant buds (range: 620-780nm; ideal: 660nm)
When cannabis plants enter the flowering period, highest yields can be achieved by exposing them to a light spectrum that contains lots of “red” wave lengths to promote budding. The rate of photosynthesis peaks when plants are subjected to “red” wave lengths of 660nm although latest NASA findings suggest that even “green” wave lengths, which are not associated as a major factor in photosynthesis, can also have an impact on how plants grow. Seeing a cannabis plant as simple photosynthesis factory is consequently a little hasty. But for now, choosing a lighting solution with a high degree of “red” in its spectrum remains the best way for growers to imitate the shallow angle of the sun in late summer and autumn. Hope this helps. Happy Growing! 🤟😜