Tracking blue light

I am growing with six 4-foot fluorescents. I’m using two daylights and four warm whites. Why do my plants tend to grow towards the blue light more than the red? Should I get another blue bulb to even it out 3 to 3?

Plants use light to regulate their growth as well as for photosynthesis. Plants use red light and infrared to regulate internode length. They use blue light to track the sun. In this case the “sun”, the blue lights, are stationary so the plants are growing towards it.

Daylights are not the best fluorescents to use. since they supply almost no red light. A cool white, 4100k lamp or a 5000k will provide larger amounts of useable light for vegetative growth. Warm white 3000k lamps can be mixed with the cool whites during flowering. They should be placed in an alternate pattern so the plants get fairly even amounts of both spectrums.

Readers with grow questions (or answers) should send them to Ed at:
Ask Ed, PMB 147, 530 Divisadero St., San Francisco, California 94117, USA
You can also email Ed at [email protected], and send queries via his website at
All featured questions will be rewarded with a copy of Marijuana Question? Ask Ed. Sorry, Ed cannot send personal replies to your questions.