Metal Halides Increase THC Content?

I read in Ed Rosenthal's Marijuana Growers Handbook that you plants will significantly increase in THC content if you switch out you HPS bulbs and put in Metal Halide bulbs during the last 2 weeks of flowering. I have been doing this and feel like I got higher when I smoked the same plant type from the same batch of seeds when I implemented this MH routine during those last 2 weeks. ( I never got my bud tested so this could also just be a placebo effect). I have never gotten bad results when using advice taken from this book.

My question is, how can you tell how much UVB output your Metal Halide bulbs are producing? Or if the correct one is being used.

you look at one of these

Yea definitely. Is there somewhere I can look up my specific bulb?

um idk try google

hexthat said:

um idk try google

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LOL yea i tried. I cant figure out how to properly search for it according to manufacturers. What im worried about is if the glass of the bulb is preventing this UVB output on newer bulbs or if those charts are from the metal halides glowing without being incased in the bulbs. I'v heard that some newer bulbs have a chemical lining that prevents UVB leaks and was wondering how i can be sure of what i got.

Ed also said somewhere about MH being worthless and always using HPS or something to that effect. I'm not sure I believe that though.

I had a friend who mistakenly used a MH for the entire grow. Yeild was shit but potency was way up there. I've tried the using MH the last few weeks and can't tell if that works or not. If I didn't care about yeild I might be tempted to use only MH the entire grow.

I think i got a thread or two about this,and it's true MH does increase trichome production in flower vs HPS,and makes buds denser.But the trade off is yield is slightly lower.

HotShot7414 said:

I think i got a thread or two about this,and it's true MH does increase trichome production in flower vs HPS,and makes buds denser.But the trade off is yield is slightly lower.

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That is true. The way to combat the lower yields is by switching out the hps for the metal halides during the last 2 weeks then plants growth has greatly slowed and trichome and terpene production occurs.

Situation420 said:

That is true. The way to combat the lower yields is by switching out the hps for the metal halides during the last 2 weeks then plants growth has greatly slowed and trichome and terpene production occurs.

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MH in flower supposed to be more of a bush effect and smaller buds then a HPS gives you more of a stretch.
running a dual spectrum you can really see the difference and yes I think there a difference in the quality but I'm not to sure just running a MH for the last two weeks

nikk2051 said:

MH in flower supposed to be more of a bush effect and smaller buds then a HPS gives you more of a stretch.
running a dual spectrum you can really see the difference and yes I think there a difference in the quality but I'm not to sure just running a MH for the last two weeks

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I don't have anyway of proving it in a lab but i would love to know for sure. It's just what I read in Ed Rosenthal's growers handbook and they seem to be right about everything else.

I just started running two 400w mh/hps together this flower period... I wonder how yield and cannabinoids would be different with 800w HPS and then 800W MH for 2 weeks at the end.

LED's work better. i switched my lights for the last 4 hrs from hps to led. increased the glands and produced a nice glaze.

I will often use a metal halide in the first 30 days of flower on strains that are Sativa or Sativa dominent. In my experience, it reduces the amount of stretch and shortens the spaces between the node growths. I am doing it now for my CBD-2 testers for Shanti @ MNS Forums:
https://www.mrnice.nl/forum/5-strain-base/11264-cbd-2-test-grow.html
You can see them there in the last set of pictures that they are sativa leaning phenos. Others have reported a lot of stretch to their testers while mine are remaining relatively shorter and packing on more nodes per length of grow shoots.
Hope this helps.
W1

silasraven said:

LED's work better. i switched my lights for the last 4 hrs from hps to led. increased the glands and produced a nice glaze.

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UV light has nothing to do with resin production and gland size. This is a common misunderstanding when it comes to THC concentration in a plant. I believe those added trichomes you saw was just going to happen anyway. LOL how does 4 hours of light have any impact on it at all anyway!?!