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Grow bible says lights on 24/7 for all veg

Greenpassion

Greenpassion

New member
I was reading the MJ Grow Bible recently, and it recommends keeping lights on 24/7 for veg, whether photos or Autos. It says it promotes faster leaf production. What about 20/4? Kind of a part of both. More than 18/6, bit less than 24/7? Just curious here. I have several Autos in with photos, and photo clones ,and auto seedlings in one room, and the photos go into room 2 for flowering. Would I benefit from Longer lights on time?
 
I personally veg with lights 24/0 because I use cfls so I want as much growth as possible in the lesser time possible. Also I don’t pay electricity so there’s that to consider. I think if you use metal halide 24 hours are unnecessary but with cfls it’s fine
 
Well, I grow with LEDs, and DO pay for electric. I'm thinking of doing g the 20/4 . WeedPharma,why do you go down to 18/6 on photos before flipping to 12/12?
 
Never grown with cfl's or flourecents . its always been my understanding that the plants need a dark cycle to "age" . Running 1000wt HID's and these new LED's I'm playing with get plenty of veg and growth with 18/6. More than enough LOL. I suppose running the lower wattage setups though 24/0 or so would be fine
 
I also use 24/0 with young plants and low power light sources, such as fluorescents. But then switch to 18/6 for the rest of main vegetation.

The current review on continous lighting shows that some plants are tolerant but others are not. And even with plants that are tolerant, they may not fully use the extra light they recieve.

Even though cannabis is apart of the c3 family where a dark cycle is not needed to complete the light independant reactions. This does not mean that plants might not benefit from a dark cycle. In the broad review on continous lighting, those that did not tolerate continous lighting. Presented with symptoms of chlorosis and reduced biomass. This has been suggested to happen because of starch accumulation in leaves, preventing adequate phloem unloading and slowing down photosynthesis as a result. This could be for many reasons. But it would likely be due to the effects from genetic expressions and or also circardian rythems.

So even though cannabis may be visually tolerant to the extra 25% more light it recieves, it may not fully reflect this with 25% more growth. For reasons previously said. So it is a lot more safer to stick with 18/6 to prevent such conditions occuring, if they do happen. Even though there is the potential for increased growth from longer light cycles, you also increase energy input per biomass produced. So you do not gain any extra efficiency in the ideal scenario. Just a reduced veg time.
 
So mj has a “rest” period where it will not produce energy even if the lights are on. If you run lights 24-7 during the entire veg cycle there will be some wasted electricity involved. Each strain will be different in how much of a rest period they require.
The growth rates of 24 on vs 18 on 6 off are not much different when compared side by side.
 
Greenpassion, It has been covered well from above posts-

Basically once the plant has 17.5 hrs of light per day, the law of diminshing returns kicks in and it's not effecient.

Also, I use light to heat the grow tent-
I veg photo's in the summer months- so not battling the daytime heat, by having lights out during the warmest part of the day.

I grow auto's the rest of the year and additional light is used for heat!

Below is some interesting information from 420mag.

(First number minimum requirement for optimal light)(Second number Maximum requirement for Optimal light)

(255 - 752 micromoles) on 24 hours daylight schedule. (VEG with 24/0)
(383 - 1128 micromoles) on 18 hours daylight schedule. (VEG with 18/6)
(510 - 1504 micromoles) on 12 hours daylight schedule. (Flowering at 12/12)

In regards to flowering at 12/12.
We want over 510 micromoles across the entire grow space for the minimum optimal growth
We want 800-1100 micromoles across the entire grow space for Maximum Optimal growth without added CO2)
We want 1,000 to 1500 micromoles across the entire grow space with added CO2 supplementation)

Anything measuring less than what is recommended above will still grow buds, but will not grow at optimal levels, so yield may significantly be affected.
​
 
Weed Pharma, that's all too scientific for me. I don't know what mycromoles are for starters or how I would measure it. All I know is that I have six 450 viparspectra lights above 6 photo plants in the 12/12 roo.m. In my veg room where I have young photos, some clones and various ages of Autos.I have (4)450 viparspectra hours and to 300 Galaxy Pro.on 18/6
 
So 9. Fingerleafs then it sounds like I don't have anywhere near enough light in either room. Is that right? With all of those 450w viparspectra?
 
"Sounds" like it according to the info above. Micromoles is another way of measuring your LED's. I've seen it explained but its pretty headie stuff. Mine are 330wt running 810 micromoles max. I'm not using Co2. The jury is out till this grow is done though. With so many lights might make up for your lower micromoles
 
You can grow some great plants with the viperspectrum 450s. They are actually about 212 watts. Trust me when I say they work great. I have lots of lights of various kinds and they will produce alot of nice bud.
 
I just hope I have enough. And if I didn't what would I do with all those 450s? I'm worried about having to go out and buy like 800 watt viparspectra or something like that. I think six of them about a foot and a half apart covering a 4 by 6 foot area or maybe a little larger than that over 6 plants should be enough. Or at least that was my hope.
 
It’s not that simple, imagine the footprint of a single light right below its 600 and 300 to the sides. So if you hang a second light next to it and combine them footprints you get 600 under each light and 600 where the sides of both footprints collide (between the two) and 300 on the edges.
So you can imagine with several fixtures any single point get lights from different sources so the overal amount of light adds up quickly. Now this are number at 24 inches of height I think. If you lower the light the footprint gets smaller and those numbers go up
 
That will just produce a bigger footprint. Not higher intensity. The distance between diodes is the same. The fixture is bigger so it consumes more electricity
 
Here are some pics to understand better. They’re HPS but the logic is the same
3B8C53CC-17E9-4B39-B1F1-B8F4641B909A.jpeg
DADBA645-A001-444C-AAE4-850E143ABB23.jpeg
 
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