Hps works thru the whole grow {veg & bloom} just fine. Some folks swear that metal halide is best, some use a combination of each. I personally dont think it makes that much difference in the end yield.

More important is to have your envrionmental conditions dialed in. Maintaining the right ph/ppm, temps, nute strength, humidity, etc will do much more for a successful end result than choosing between hps or mh light. Cfl's dont have the lumens output to get the photosynthesis going in high gear. They will grow plants, but dont have the "penetration" or strength to grow big buds and colas unless you have a whole bunch of them, and floro grown buds are always smaller. High pressure sodium {hps} gives off more initial lumens than a metal halide. A good rule is to use the biggest lite you can get as long as you can control the heat output. We use a 1000w hps in winter when it is cooler. Then during the summer we use a 400w hps when heat is more of a problem. good luck
oldnslow Reviewed by oldnslow on . Best Light for Flowering? What is everyones preference as far as flowering lights go? I was going to use a 400w HPS light for vegetation and haven't decided on flowering lights yet. Rating: 5