When you are growing marijuana indoors, you need to artificially recreate many factors of growth which are otherwise present naturally outdoors. One such factor is sunlight - which is very important for the growth of plants. Using a full-spectrum LED grow light ensures that the plants are getting proper lighting. Lighting is very important because light helps the plants produce chlorophyll and photosynthesize properly, as well as helps it in various other processes of growth. A full-spectrum LED light ensures that the red as well as blue spectrum of light is provided to the plants which helps them grow through their vegetative phase as well as the blooming/flowering phase. This is the reason LED lights are important.