Spectrum of Grass

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   Grass is a "solid" object and thus radiates a thermal blackbody spectrum. However, grass isn't hot enough to radiate significantly in the visible part of the spectrum (it does radiate in the infrared, however). Like most normal objects, it is seen visibly by reflection. If illuminated by white light (e.g., sunlight), the visible spectrum of grass will be as shown above. The blue and red portions of the illuminating light are absorbed by chlorophyll so that only the green part is reflected.
   Since chlorophyll doesn't absorb green light, light bulbs used for growing plants indoors need to provide only blue and red wavelengths (as seen in the spectrum of a Gro-Lux© bulb).