HPS + CMH = reduced flowering time

All my plants seem to finish a week earlier than when other people grow the same strain. This has only been the case since I added CMH lighting in addition to my gavitas.

Has anyone else found this?

In a way CMH gives new meaning to the term flowering lamp. Limited experience growing under sodium lamps although it looks clear that HPS gives a distinct flower appearance. CMH flowers appear either slightly more leafy or more like sun grown. More elements which do not fit a category of yield mass or percent resin etc. You can see halide compared to LED compared to sodium compared to sun grown in the flower in aspects other than size or finishing time. As far as I know this website is the best resource available for deciding how well each light source performs. A blatant sales post saying new lights excel in every category will appear that way. At the same time however it is easy to grow side by side or together and post pictures and draw conclusions.

Giving it a go

Giving it a go

Im currently flowering under to 600watt hps an 3 315 cmh in a 2.4x1.2 metre grow tent will be interesting to see how it goes

NzGreenWhanau said:

Im currently flowering under to 600watt hps an 3 315 cmh in a 2.4x1.2 metre grow tent will be interesting to see how it goes

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That is more than 50W/ square feet. No heat issue?

I'm using 2 150w cdm(osram hci-t 150w/942) and add 250-400 w dimmable hps from wk3 flowering for some years now and noticed also that the plants ripe early with that combo. Downside is the 150w get used up very fast. After 1/2 year u notice a drop in light intensity but the last bulbs i got were about 5 euro/ piece . Also the buds got bigger and g/w went up. The flowers look different, didn't get the late foxtailing with trainwreck.

Was thinking alot if 2 x 315w cdm and 1 x 750w de hps on a lightrail would be enough for 120 x 240 tent.
How do u position them NzGreenWhanau? Hps in the middle or between 2 cdm so one side got more hps light?

I think sodium flowers the slowest as it looses time during the first two weeks.

Sodium is the most biased lighting towards the red. With lots of IR far-red and orange, but so little blue that you need a lot of sodium lighting to meet the minimum blue illumination requirement for growing anything reasonable. This tilt towards the red causes stretching. It's proven using bands of light, or by just growing a plant. A plant showing a shade response isn't very interested in flowering. Flowers are no use. Flowers above all the others in a field are what it needs. It's stretch first, flower later.

While far red penetration has been shown to trigger a shade response, I have no reason to believe it's the only trigger. Monochrome red/orange also causes stretch, while just green doesn't. Just blue would be interesting but I can guess.

I think a spectral tilt towards the warm slows flowering by inducing stretch.

I have played about with this. Adding incandescent lamps to leds to see more sodium like growth.

Along with the Daily light intergral, there is possibly a crop light intergral. Where a certain amount of photons are required to finish. Maybe it's blue one's. While counting them we can keep the red one's coming. I have seen lower yields along with the quicker finishes which leads me to think this way. Perhaps chilli has the right idea. Getting into the swing of things with mh before bringing in the big gun.


Good topic. I reckon I might pull a few gems from it if it keeps going.

I did this accidentaly. Tried 2 x 150w in a medium adjust a wing and got genetics that grew big plants with small flowers( austria power kush, sleestack x skunk) so i added the hps and the flowers got bigger but the normal developed buds exploded so never looked back.
I like that the internodes grow short the with the cmh and imo the better potency/effect.

madalasatori said:

All my plants seem to finish a week earlier than when other people grow the same strain. This has only been the case since I added CMH lighting in addition to my gavitas.

Has anyone else found this?

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HI !

Very nice observation by yourself . Congrats

It is ( not so well ) known that using separate spectrums for growing ( white / blue) and flowering makes you save more or less than a week .
I don't remember which book noted it .

When you do all under same spectrum , you don't win this week .

That's why breeders infos sometime means nothing, because it is all in user hands to choose the correct formula for nice environment .

Mars Hydro Led said:

That is more than 50W/ square feet. No heat issue?

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Sorry for the late reply I had the 600 watt bulbs in cool tubes an they were on at night I ended up turning on of the 315cmh off as the temps were sitting around 30 degrees Celsius. Once i did that they leveled off at around 26-28

chilliwilli said:

Was thinking alot if 2 x 315w cdm and 1 x 750w de hps on a lightrail would be enough for 120 x 240 tent.
How do u position them NzGreenWhanau? Hps in the middle or between 2 cdm so one side got more hps light?

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One half was 600watt an 315 then the other half was 315 an 600 hope that makes sense

NzGreenWhanau said:

Sorry for the late reply I had the 600 watt bulbs in cool tubes an they were on at night I ended up turning on of the 315cmh off as the temps were sitting around 30 degrees Celsius. Once i did that they leveled off at around 26-28

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Sounds like a good idea! Good luck.

Mars Hydro Led said:

Sounds like a good idea! Good luck.

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Thanks finished that garden at the end of 2020 did alright ill be definitely doing it again

NzGreenWhanau said:

One half was 600watt an 315 then the other half was 315 an 600 hope that makes sense

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More then my question