Putting cmh to the test

Gonna see how cmh does finally. I know at this point the cmh train has been chugging along for a while and the results are in but I'm going to do it for myself.

I have always been happy enough with hps but I found myself having heat issues with summer coming. In one corner of my room I was running a 5x5 with a 1kw hps over it, close to 40 days from flip, flowers showed 13 days into that. Just exchanged the hps for a 315 cmh. I know that's way too little light for the area but the temps were in the high 90's the last few days before the change before that the temps were fine.

So basically what I'm doing is seeing how the 315 can do on a 5x5 IF the first half of flower was done with a 1kw hps.

growingforfun said:

Gonna see how cmh does finally. I know at this point the cmh train has been chugging along for a while and the results are in but I'm going to do it for myself.

I have always been happy enough with hps but I found myself having heat issues with summer coming. In one corner of my room I was running a 5x5 with a 1kw hps over it, close to 40 days from flip, flowers showed 13 days into that. Just exchanged the hps for a 315 cmh. I know that's way too little light for the area but the temps were in the high 90's the last few days before the change before that the temps were fine.

So basically what I'm doing is seeing how the 315 can do on a 5x5 IF the first half of flower was done with a 1kw hps.

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A 315 cmh covers 3x3. In my 5x5 I have 2 315s and a blurple. I would go back to the 1kw till you can score another 315.

What exactly is the experiment?

Antitheist said:

A 315 cmh covers 3x3. In my 5x5 I have 2 315s and a blurple. I would go back to the 1kw till you can score another 315.

What exactly is the experiment?

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It was too hot I'm my room with 2 other 1k's. I could cut down that area 40 days into flower or I could try this. It was 90-100 in the room before the change an now its 78.

It's to see what happens

growingforfun said:

It was too hot I'm my room with 2 other 1k's. I could cut down that area 40 days into flower or I could try this. It was 90-100 in the room before the change an now its 78.

It's to see what happens

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Now it's making some sense.

Antitheist said:

Now it's making some sense.

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Ya I figure it will be fine, even if I dont get "max yield" it will be better than ripping them. They are looking good so far an even if they dont turn into big buds I want to see how it goes. If it turns out well I may use it as a strategy in the future. As fall comes theres naturally less light outdoors anyways I figure. And at 40 days from the flip they were already developing good buds.

I'm along for the ride as I'm interested in seeing your results. I actually had a very similar situation as you, and I really love my CMH light. It produced surpisingly thick, dense buds that just really caught me off guard. I swear, if I didn't know better, I'd say I got denser flowers off of my 315w CMH in a 3x3ft grow tent than I did with my 1000w HPS 6.5x6.5ft grow tent. When cooler months roll around, you could always run the 315w cmh along side your 1000w? When winter months roll around, that is. I will say this though, when I moved my two autoflowers out from under the 1000w and under the 315w cmh, I encountered a very very severe cal/mag deficiency. Perhaps it was the bigger, wider spectrum, perhaps it is the UV in the spectrum, but something related to the CMH light triggered my plants to eat a lot more cal/mag.

They will definitely drink less.

Renfro said:

They will definitely drink less.

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Ya it will be nice to have to haul less water. I honestly dont even care about lower yield as I've already got enough to last me. This was a ill timed test run for a double layer scrog. I normally do single layer. The results look good enough that my main area is a double layer now under the gavitas.

6 days in and the cmh is doing really good, even over the 5x5. It's probably because they started under 1kw hps, but it seems like they are continuing to grow just fine. I'm really looking forward to this crop because it seems like they are frosting up a lot

Day 49 from flip an 11 days under the cmh and they are filling in really really well. I'd say it's pretty much the same as when I do a 1k hps the full cycle as far as I can figure. I have been taking this clone at 70 days but I want to see if I can take it to 80 this time and see how they come out. If I get 20 oz it will match my average when running hps the full cycle, and from the current look of things I'll be surprised if I dont get it. Thing look frostier than normal as well but it's hard to be sure

Averaging the 1kw with the 315 gives me around 700 watts used for the cycle. The 315 is only on for 10 hours as well, but there are 2x 1kw gavitas about 7 ft away on for a hour before and a hour after that wake the plants up and put them to sleep. Theres no direct light from them though so I dont think they are adding to the yield any

Not a chance 1x315 CMH = 1k hps. Im a Cmh grower for almost 4yrs now. You'll need 2x 315 or 1x 630 to even come close.

You can pull 3/4lb with 1x315 easily with a dialed in grow and the proper genetics.

growingforfun said:

It was too hot I'm my room with 2 other 1k's. I could cut down that area 40 days into flower or I could try this. It was 90-100 in the room before the change an now its 78.

It's to see what happens

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In your situation, I'd run two 315W CMH lamps to replace one 1000W HPS. You'll like the results; similar yield, better quality, less heat load, lower energy bill.

DemonTrich said:

Not a chance 1x315 CMH = 1k hps. Im a Cmh grower for almost 4yrs now. You'll need 2x 315 or 1x 630 to even come close.

You can pull 3/4lb with 1x315 easily with a dialed in grow and the proper genetics.

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I guess I'll find out wont I? Keep in mind it wasnt under the 315 the whole time. Theres a big differance between using a 315 the whole time and only using it for the second half. Sure, 2x315 would cover the space better from start to finish but it seems to be just fine like it is <shrug>

I know what differant amounts look like and frankly I'll be shocked if it's only 3/4 lb. Looks like 16-20 imo

growingforfun said:

I guess I'll find out wont I? Keep in mind it wasnt under the 315 the whole time. Theres a big differance between using a 315 the whole time and only using it for the second half. Sure, 2x315 would cover the space better from start to finish but it seems to be just fine like it is <shrug>

I know what differant amounts look like and frankly I'll be shocked if it's only 3/4 lb. Looks like 16-20 imo

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You would have been better of running your cmh through veg and about a month in flower then switching back to hps for final month of flower. Your doin things backwards. Plants need lots more light for flower, less in veg

PURPLEB3RRYKUSH said:

You would have been better of running your cmh through veg and about a month in flower then switching back to hps for final month of flower. Your doin things backwards. Plants need lots more light for flower, less in veg

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Yeah that sounds good on paper but in practice running CMH all the way through gave me the best results, both in terms of yields and quality.

How many plants are you growing in this experiment?

PURPLEB3RRYKUSH said:

You would have been better of running your cmh through veg and about a month in flower then switching back to hps for final month of flower. Your doin things backwards. Plants need lots more light for flower, less in veg

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Maybe you missed the part where I was mid cycle with 3kw running total and my ONLY option was to cut them down and turn off the light, or buy a 315 and hang it and keep them alive.

Exploring what would be best would probably lead along a path including ac for the room, and Hookers who bring me cocaine and blowjobs when they wanna relax after work

I cant change the situation that lead to replacing a 1kw over a 5x5 with a 315.
All I can do is share the results of what's happening. So far the results are great... so...


An if you look at nature, they actually get most light in late veg till early mid flower then less at the end.

Flatrate said:

How many plants are you growing in this experiment?

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9 plants. They all look good so far

I'm pretty sure I mentioned it above, but if I didnt, i also replaced my 1kw in my veg area with a 315.

I'll get to see how the next cycle goes with veg under 3500k 315cmh to flowering under 3000k 315cmh. I'll still flower it over the 5x5, because that's the size of the area. Dont care that it "wont work" or whatever I'll turn any junk into hash so it's not gonna matter if half the area is full of larf. Everything over the current run is nice dense buds tho.

Following along.
I flower in a 4 x 4 and found a 600w HPS a bit hot in summer. I upgraded to a DE630w CMH. Its cooler- that surprised me. More frost and denser buds. CMH really does bring out the oil.
Be interesting to see how u go and what you think.