E-mail -- How Close to Put HPS for Clones

Dr. E.R. Myers
I just bought one of your 400 hps lights.....things are looking good.....I'm curious as to how close is normally a good distance to my vegging clones....they are a few weeks rooted...I know it's too close if  they burn (grin) I just wonder how close do people run 'em?? Thanks


The heat is the real problem. If you have a light fan blowing over the plants or an air cooled light you can keep the HPS within 2 feet. I usually keep My 400 HPS light about 3 feet above the plants that I grow.

Do you use the HPS as your only light? This is ok, as I have written about before  but... I usually recommend a fluorscent for early cuttings and seedlings. The HPS will also decrease the humidity in the room which is good for flowering (no mold) but not good for vegetative cuttings which need a moist environment for the first couple weeks. Do you have a thermometer with min/max and humidity readings? That is a good tool to have and will let you know if you need to adjust things to maximize growth. A good rule of thumb is if your temps. are in the 90’s and higher by the plant tops, move the light up. If you can’t get the temperature below 90, you need to ventilate the room or switch to LED or fluorescents.
I hope this helps,

Good growing,
Dr. E.R. Myers

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