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LED vs HPS day 39

LED grow lights .. do they really work? As followers of this blog will know, I’m running a series of experiments putting various LED grow lights up against traditional HID lighting for an indoor marijuana grow.

Fero 360 4G LED grow lights cannabisMy last post showed the plants – 8 MI5s (2 of them fertilized for cannabis seed production) divided up underneath a 250 watt HPS dual spectrum and a Fero LED 357 – and marked progress up to day 22. This post does a bit of catching up, and brings us to day 39.

The grow has progressed without hiccups for the past 17 days. I’ve lowered the pH slightly to 5.8 and increased the vegetative food to 3/4 strength applied with every water. (Plants are in a coco-perlite mix and get watered every other day until there is a 25% runoff). I’m still using veg nutrients at this stage – even though the plants are in flower – as the breeder of this strain recommends keeping them in veg food until upward growth has stopped around week 6.

I’ve been taking advice from some experienced guys who use LEDs for cannabis autoflowering grows, which is basically that the reason why my MI5s are so short under the LEDs is that they need to be encouraged to stretch up to the plentiful light source … hmmm seems like everything I used to know about growing under HPS is being put into reverse! Still, they have some excellent documented autoflowering grows, so I’m following suit. The LED is (for now) raised to 20″ above plant tip whilst the HPS, being only a 250 watt is managing to get as close as 12″.

I have received an email from FeroLED saying that they are going to discontinue the 357 range (unless specifically requested) as they have a new 4G series with a 90º double lens, high powered grow lights. This new range has loads of new pluses, and if you want to read the technical info, please click here. I’ve been lucky enough to get my hands on two of these lights – one is the sexy looking top of the range Fero 900 4G – and the other is the 360 4G.


Now the draw on the 357 3G is only 120 watts and I’m trying to compare it with a 250 HPS: in my opinion its in danger of losing the showdown. Its a fantastic mother/seedling light, and I do intend using it as an example of how to do a stealth grow box, but right now, pitching LED against HID, it just isn’t quite man enough. The new 360 4G however, has a 256 watt draw, so is more competing like for like. Only wish I’d had it 39 days ago! Oh well, its an excuse for another showdown trial in 2012! For now I’ll swap the older 357 model for the new 360 4G for the rest of this grow.


led grow light vs HID lighting for marijuan


LED grow light cannabis





MI5s under LED grow lights:

  • temperature range: 18ºC – 25.5ºC
  • rH: 55- 72
  • heights: 25cm, 25cm, 32.5cm (9 3/4″, 9 3/4″, 12 3/4″)
  • solution uptake every water: 4.2 L for 4 x 10L pots
There’s starting to be a marked difference in height between the two groups, and a slight difference in flower formation.
Here are the 3 cannabis plants under the 250 HPS:





MI5s under HID grow light

  • temperature range: 18ºC – 27.5ºC
  • rH: 50 – 72
  • heights: 34cm, 40cm, 47cm (13 3/4″; 15 3/4″; 18 1/2″)
  • solution uptake every water: 5.5 L for 4 x 10L pots
There’s one point I think we should take into consideration with this as I am noticing two different phenotypes emerging in the MI5 strain. One type is taller, more lanky, whilst the other is about 25% shorter with more side branches. I say this because the smaller of the 3 under the HID looks very much like 2 of those growing under the LED. With only 6 plants in play, there is a possibility that chance played a role in the distribution of plant phenotype – or is it wholly down to the lights?
OK so that’s it for another week. According to the seed statistics, we are now roughly half way into this grow. Time for you little beauties to start putting on bud growth!
Postscript – the three mums who were fertilized with the MI5 male are all happily pregnant – you can see the seeds swelling inside the flowers.The Barry White medley seems to have worked!
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  • Can you give us an update with the new FERO you got, I have the smallest 4G unit, just wandering how the light is working for you

  • Hi Jean Paul … sorry to be so late getting back to you: only just picked up your comment! I’m reorganising the site so hopefully it will make it easier to follow blog posts on a related subject .. and am in the middle of doing a piece on the results of the trial right now: expect it this week. You may also like to read Max’s Grapefruit Kush grow as he’s new to growing and new to the 4G light system too so campo gave him some advice on how to grow using these lights.

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