Good flower production, dense growth, high productivity and yield.
#Best color light for seedlings full#
The results were very interesting.įlowering plants and lettuce grown under Full Spectrum (white) light. We tested each grow chamber with a PAR (Photosynthetically Active Radiation) meter and adjusted the grow light output and hanging height to make sure each chamber had the same average PAR level. The light intensity in each growth chamber was the same. We ran a grow comparison under blue, red and full spectrum light over three weeks to see what growth would result. We setup three grow chambers with flowering plants and productive edibles. McCrees action spectrum is the correct reference for assessing the suitability and effectiveness of a grow lights spectrum output.Įxperimental tests of the effects of Blue, Red and White (Full spectrum) light McCrees action spectrum identifies what colors of the visible spectrum are best for photosynthesis. The quantum efficiency for red is close to 100% efficient whereas blue and green were less efficient, ranging from 65% to 75%. McCree discovered that plants use all parts of the PAR spectrum but at different rates. In other words he recorded the rate of growth of plants exposed to each wavelength or colour of light. He assessed the relative quantum efficiency of different wavelengths of light on photosynthesis. In the 1970s a scientist called McCree determined the wavelengths of light a plant can absorb. If green light did not photosynthesise then 50% of the light output of HPS bulbs would be ineffective. HPS bulbs generally output about 50% of their light in the green spectrum. For example HPS (High Pressure Sodium) bulbs have been the preferred grow light source for decades. In fact, all colours of light in the PAR spectrum contribute to photosynthesis and growth, just at slightly different rates. This is incorrect and is an argument constructed to support the sale of red and blue LED grow lights. They make the case that green light is not absorbed by plants at all. They are based on absorbance of light by chlorophyll extracted from leaves and tested in a laboratory test tube. These graphs are not the entire picture and are misleading. To support the use of only blue and red LEDs for horticulture they reference Chlorophyll absorbance graphs. So early grow light manufacturers used the LEDs available and made the first LED grow lights.
Up to a few years ago only Red and Blue LEDs were available for 'high power' (3 watt, 5 watt) applications. This is not the total light absorbance of plants in real life Absorbance graph of Chlorophyll and Carotenoids in a test tube.
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