A grow light or plant light is an artificial light source, generally an electric light, designed to stimulate plant growth by emitting an electromagnetic spectrum appropriate forphotosynthesis. Grow lights are used in applications where there is either no naturally occurring light, or where supplemental light is required. For example, in the winter months when the available hours of daylight may be insufficient for the desired plant growth, lights are used to extend the time the plants receive light.

here are multipleabsorption peaksfor chlorophyll and carotenoids, and LED grow-lights may use one or more LED colors overlapping these peaks.

It is also often published that for vegetative growth, blue LEDs are preferred, where the light has a wavelength in the mid-400 nm (nanometer) range. For growing fruits or flowers, a greater proportion of red LEDs is considered preferable, with light very near 600-640 nm, the exact number this wavelength being more critical than for the blue LED.^[2] (Actually the cited reference says it uses exactly three wavelength, 470nm, 612nm and 660nm, the 612nm one targeting not photosynthesis as such but carotenoids.)