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315Watt CMH Lighting: Specs, Coverage, Pics

Do you think CMH is a viable alternative to LED?

  • Yes

    Votes: 36 70.6%
  • No

    Votes: 5 9.8%
  • I need to read more.

    Votes: 7 13.7%
  • Isn't a Poll a sheep.

    Votes: 3 5.9%

  • Total voters


Well-Known Member
Thats an awesome comparison set up you have there geo.
Are you just running the autos at 12/12 with the 2 photo plants? Just because I thought autos are supposed to be 18/6 or above.

Hey Urbs, they sure do make plants grow healthy. Nice looking bud!

Im still playing with my cmh, trying to find their sweet spot.
I got some focal reflectors so next run should be good.
What tempurature bulbs are you using?
I see good results with ones around 3100K, mine is 3200K.
Was just wondering if people tried the 4000-4200K bulbs all the way through, and what resuls were like compared to my 3200K.

Just harvested....., 2 x 315w CMH,
9 plants in 20L pots, no enviromental controls, 4' x 8' tent....now drying tent..

That be an easy 2 pounds when dry. Got that last time in 10L pots, so should be a bit more than that I hope, for the extra 10L pot size each.

Happy Growing!
I've got the autos already above the surface, and soaking the photos now. I figure I will veg the photos for 8 weeks, and any autos left at that time can finish up while the photos do their stretching after the flip.

I will be letting the autos go natural, and LST the photos.


Well-Known Member
Hey @GeOMaTTiC , how did your autos go? Hopefully they loved the CMH.
My lights are on holiday for summer.
Dont forget to drop your CMH results and pics guys!


Well-Known Member
They are doing excellent.

One is a new strain to me from Garden of Green, GDPxGumberry

The other I've already grown under a Phlizon LED, NLxBB from Oasis genetics.

So far the NLxBB under the CMH is much bigger than the first round, but I can't yet fully confirm if the small plant was my fault, genetics, or the light. I assume it was the light, but I will be testing that theory out soon enough

GDPxGumberry on left, NLxBB is on the right, both are just a out 5 weeks old.

No training or defoliation, just some tucking of leaves when they were smaller.

First NLxBB was trained, and after seeing this beast, I want to try it training the next one. While it's pretty even as is, I'd rather keep everything level.


Hi All, First post on this forum. I'm running 2 x 315CMH in a 4x4 tent as I researched that one does a 3x3 tent so hence upping the lighting. Currently doing a GSC Auto grow. They are 4 weeks most started to head. They do vary in height a bit though which is confusing considering all are in the same soil, nutes etc. The higher ones are not as dense and internodes are quite spaced out. Others are closer spacing but not as tall. Time will tell...

My last grow was period SSH. Amazing results.
I'm a CMH convert for sure.


Isn't that what your supposed to do? LOL, Gee thanks for the warm welcome! LOL I have a long memory! LOL
There's another strain in front that needed "training" as it really stretched. There was 2 SSH behind this one. The SSH's were heavy yielders.

The Physicist

Well-Known Member
I recently upgraded to the Hortilux 315 CMH. I recorded the spectrum below compared to sunlight. Note they don't show the full range of the spectrum on the box. The Bulb extends all the way to 350nm and all the way out to 850nm giving a much closer sun like spectrum than any other bulb. I previously ran the Phillips 3100k but upgraded to the extra UVA and IR band energy.
Hortilux 315W:
hortilux 315 cmh.JPG

Sunlight Noon California:


Well-Known Member
I'm noticing some very impressive growth compared to the LED. They both have their merits, but I think dollar for dollar, CMH is the winner. The high end LED are something I only dream about, as I don't have any reason to switch.


The Physicist

Well-Known Member
I am running LED only in veg, purely because the required umol/s is about 300-350 which is overkill unless you are at >24” above the babies which at that point you are wasting energy with minimal efficiency in regards to plant growth. Flowering CMH allll the way 100%, but I use blurple undercanopy/side lighting.


Plant of the Month, June 2020
One 315w CMH, Im using the Phillips 4200 bulb for veg and will swap in a Phillips 3100 for flower. First grow I swapped as soon as I saw pistils. This 2nd grow I intend to swap in the 3k after stretch is complete to finish flowering the last 7 weeks or so. Does this make sense to you experienced growers? Picture is end of 2 weeks from flip to 12/12...figure stretch will be over in another week or so.

The Physicist

Well-Known Member
Imo could have switched when you flipped. Hortilux doesn’t even make a 3100k version because the difference is so small in spectrum its mostly marketing. Your plants are looking great! Keep on chuggin along
:bravo: :Namaste:


Well-Known Member
Just got a couple 315's with vertical hoods, 3100k bulbs & dimming ballasts.
Cheap Chinese no name stuff but the build quality is pretty decent. $120 per light shipped!!! We will see how they do.


Loving them so far!!!


Three Birthday Cake clones in DWC. Day 36 of veg from cutting. Check out the details in my journal. Would love some feedback from the CMH community. I'll post updates here too.

Gg4 guy

New Member
I’ve been looking at CMH for a couple years. Lots of enticing comments from users.
But- whether true or not, some mainstream sites on the net continue to tell me that everything else aside CMH somehow isn’t as well tailored to flowering as some of the other options and will give inferior buds to LED or HPS.
Flowering is obviously where the action is. Anything can veg plants. I wantz budz !
I know its a year old thread but this was grown with cmh



Plant of the Month, June 2020
Grow #2 buds stacking 4.5 weeks from flip to 12/12. Swapped in the Phillips 3k after stretch. While there is a noticeable pinkish hue v the whiter Phillips 4k (used in veg), its not as bad as it looks in the one picture. Very frosty and very smelly at this point. Getting some nice purple and wine coloration on the upper fans.
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