E-mail - MH vs HPS Flowering and Vegetative Growth

Dr. Myers
I recently purchased a 1000w digital system from HTG (http://htgsupply.com/Product-Digital-Greenhouse-1000-watt-HPS-Grow-Light.asp)
I thought I grew with HPS and flowered with MH.(they state that on another web page) I called HTGSupply.com and they say it is just the opposite.
Which is correct?
Also, there are several versions of MH that work with my system an MH 6500K (sounds like a grow bulb to me) an MH Neutral, MH Warm,MH Cool.
What MH bulb should I use and when should I be using them...Thank You very much.

Thanks for your question, it is important to know!  Let me  try to clear this up...
You grow with MH during vegetative because it has more blue light which promotes vegetative growth. You use an HPS for flowering 1) because it has more yellow light which encourages flowers/fruit and 2) the excess yellow will also cause plants to grow tall and without wind or shaking some plants get lanky and fall over. Plants naturally have slow then no vegetative growth when then flower so this is not such a problem when using the HPS during flowering
If I may quote the HTGSupply.com website, good growers worldwide agree that growing with Metal Halide during the vegetative stage, then switching to High Pressure Sodium for flowering is the way to grow the BEST PLANTS POSSIBLE. This method gives you the thickest, most lush plant and the best yields!

I talked about Kelvin before on the blog (LINK to Kelvin post)
You are right the 6500 K would be for vegetative growth, and it would be the one I would recomend you use for vegetative (It could be used for flowering too). However, for the light you bought, the idea / benefit is the you can use the MH for vegetative and then switch the bulb over to the HPS when you flower, HPS is usually around 2200 K.
Good Growing
Dr. E.R. Myers

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