How far from flower tops should a LED grow light be?

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Q:

I love reading Maximum Yield magazine! Learning is my passion! Thank you for the article, “The results…LEDs three and a half years later.” I have an LED grow light and my first question is how far away from the flower tops should this light be kept? My second question is about good nutrients to add to boost taste, flavor and, of course, yield in my finished product. Thank you for answering my questions. Growing like crazy in Nor Cali!

A:

For the LED light distance from the canopy top question, I would have to say the rule of thumb for lights is generally to keep them 1 foot away from the top of the plants. This is the distance the lumen ratings are given, I believe. But LEDs can be placed closer because they are cooler. I would try maybe 6 inches away and just monitor your plants for any sign of wilting or leaf burn—telltale signs that it is too hot for the plants. You can usually tell just by putting your hand there. The benefit of moving the lights closer is that light diminishes exponentially as it moves away from the plant. By moving it closer, you are effectively increasing the light strength. While moving lights closer increases light strength up to two fold, you will also lose some coverage this way, so it is a toss-up.

As for bloom and flavor-enhancing supplements go, I am a big fan of humid acid, often labeled “black,” and fulvic acid, labeled “gold.” Fulvic acid can be mixed into a foliar spray and will increase the number of flower sites. I also really like organic soluble bat guano, just make sure it is from a sustainable source.

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