A 6/2 Light Schedule Could Increase Plant Growth

A 6/2 Light Schedule Could Increase Plant Growth

Posted by Celia Daly on March 10, 2016 12:00 am
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Many growers advocate the use of an 18/6 light schedule (18 hours on, 6 hours off) while plants are in Veg. However, this may not be the most beneficial light schedule. Switching to a series of 6/2 (6 hours on, 2 hours off)  light patterns may increase plant growth while also potentially creating a more stable controlled environment.

While this new schedule may sound risky, it actually comes with a number of benefits.

Cannabis is a “short-day plant,” meaning that it will only flower when exposed to long periods of darkness and short periods of light. For cannabis to flower, there must be at least 12 hours of continuous darkness. This allows for the use of a series of shorter light schedules while the plant is in Veg – as long as the plant receives less than 12 hours of continuous  darkness, it will stay in Veg.

Benefits of a 6/2 Light Schedule

There is a lot of research that suggests that cannabis plants can only process a certain amount of light per day. After that level has been reached, the plant can no longer absorb more light, and any additional light is essentially wasted. By breaking the light cycle into multiple 6 hour periods, the plant is able to rest and process the light it has received. When the lights come back on 2 hours later, the plant will be ready to process additional light, allowing you to get the most plant growth out of every minute your lights are on.

At a biological level, cannabis’s inability to grow more once it has received a certain amount of light can be attributed to the way the plant processes carbon dioxide (CO2). A majority of the mass accumulated in cannabis is associated with the amount of CO2 found inside plant cells. While under light, cannabis tries to prevent CO2 from leaving its cells by cutting off transpiration. However, this prevents new CO2 from entering into the cell, blocking new growth. When the lights are turned off, and no photosynthesis is occurring, the plant is able to absorb new CO2 into its cells.

Additionally, when plants are exposed to 18 straight hours of intense light, they become stressed. Signs of stress – droopy or curled leaves – will usually appear towards the end of the light cycle. While some stress can be beneficial to plant growth, too much stress can cause harm to your plants and prevent them from reaching maximum growth potential.

Giving plants 6 hours of intense light at a time not only puts less stress on the plants, it also spread out the load on your cooling system over a longer period of time. The cooling system works the hardest when lights are on. By turning off the lights for 2 hours at a time throughout the day, your cooling system will get a break between light cycles, allowing the room to be cooled to desired temperatures before the lights come back on. With a properly sized cooling system, this benefit will be minimized as the system will be designed to handle the heat load throughout the entire light cycle.

While there are many approaches to Veg light cycles for cannabis, a 6/2 schedule allows for maximum plant growth. A 6/2 schedule allows plants to process more intense light, prevents plants from becoming stressed and puts less stress on your cooling system. It’s a win all around. Give your plants a break every 2 hours and you’ll be amazed at the results.

Topics: biology, california cultivation, Cannabis Basics, featured, lighting, plant growth

7 responses to “A 6/2 Light Schedule Could Increase Plant Growth”

  1. Jim Nguyen says:

    Do we have viable proof of this? Have you ever tried it? Just curious because I am interested….

  2. Jino says:

    I am going to give this a try. I’m currently trying a 5/3, but I suspect it’s not quite long enough for the chloroplasts or mitochondria or whatever to max out. I heard the top out time is faster with leds than a gaslamp, but who knows, pr to pfr is targeted with led band so maybe it happens sooner than a with a wide band, it’s like force feeding a goose! Hid systems say rest after 4-5 hours, so without light to toggle or an ancillary/aux you can’t meet the six, but maybe it’s worth a bulb or two. I like the droopy foliage during the dark period, sweet dreams!

  3. TgSmarTGuy says:

    I just started this 6/2 for my blue chem let see how it goes!

  4. Dom says:

    How should it be transitioned to flower when using 6-2 cycle?

  5. Peta says:

    I tried this, plants grew well and I guess its easier on the gear ,but they grew no better than 18/6 and they took twice as long to come into flower when switched to 12/12 ,using a cloned strain from 1 year old mother so I know what to expect from the strain, only difference 6/2 schedule , my thoughts are the short 6 hour light days interrupt some mechanism when switched to 12/12 the day has actually doubled in length for the plant not shortened as should have happened and it takes a while to adjust to something unknown but known now you know,how the plant feels.stick to normal light schedules is my advice, Hermies could arise because the stress event is occurring in flowering because of the short days in the veg period. Petapullthrough@humbolt

  6. Peter p says:

    See what happens come flower time,it took my plants 5 weeks to even start to grow pistols, 6 hours light 2 hours dark then you change to 12/12 think about it , shortening days make it flower ,not doubling the day length.

  7. Anon says:

    Works like a dream.

    This is the only method I’m aware of to eliminate light stress when using high end lighting. 600/1000 SE/DE – cobs or quantum boards.
    It also allows the use of more intense UV-A/UV-B T5 supplemental lighting without burning.

    The 6/2 is a good option for autos as well.

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