I do it cause I'm lazy, one less timer i gotta set up and think about.
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Why go 24 hours lights on??
- Thread starter thcrefugee
- Start date
People who have actually done it, you know that thing called "experience" Go out and get some instead of making threads to show you don't have it.
Fear
Member
only reason to go to 18 hours is to save a little money on electricity. You will obviously get rapid growth at 24 hours but for me when I have 4 8 lamp fixtures over clones I don't mind a lil rest on the ol PG&E. Never noticed a difference either way. I'm at 24 hours now. But I like 18.
mdk ktm
Member
I have always done 24/0, and everything is doing great. I could try 18/6 next time to see what it does. That amount of power saving doesn't mean shit to me if there is going to be a huge power spike. I like running steady continuous power. 2 12/12 bloom rooms and a veg room going 24/0.
thcrefugee wrote
I think people use light on 24/7 because they want to (unwittingly) grow less healthy plants; plants that do not have as high of a rate of photosynthesis and rate of growth as plants using proper diurnal (daylength) time, ex. 20 hours max. Plants use night time even in veg to carry out "light independent reactions" (formally termed "dark reactions") such as calvin cycle, circadian rhythm, etc.
Plants grow the most during the night and very early morning hours...by far.
That said, plants can do without a night time, but it's not a great idea.
Not using a night hinders most plants and shows how much cannabis book authors do not understand plant physiology and photobiology. It's really a shame that the likes of Mel Frank, Ed Rosenthall, Jorge Cervanties, etc., perpetuate the incorrect claims that plants do fine when they don't have night. That claim is total BS in terms of rate of photosynthesis, rate of growth, level of plant stress, calvin cycle, circadian rhythm etc., etc.
Plants need night time for the best growth. Plants can grow without a night but they have reduced rate of photosynthesis, reduced rate of growth, reduced carbon assimilate and partitioning, etc., etc., et al.
Also, Ca is transported within plant (xylem) most efficiently during the night IIRC.
Another issue with providing light 24/7 is "photoinhibition" of plants. The problem is the "Daily Light Integral" (DLI), which is the total amount of light (i.e. photons within PAR range) that irradiates the plant per day (as moles/area/day). Too much DLI is just as bad as too much light (as a single instance measurement with Lux, PPFD (umol), etc) in terms of hindering the plant's biological process. Namely by reducing stomatal conductance that in turn reduces the rate of photosynthesis, Co2 fixation, calcium and boron movement into roots, etc.
DLI is a very important factor and one that is lost on most people, sadly. Lumens, lux, umol (ex as PPDF; Photosynthetic Photon Flux Density), etc., are single instance measurements of light. However, we need to consider the sum of light over the whole day, not just for a second. In other words, we should not be using lumens, lux, PPF (umol/second), umol/area/second, etc., to judge how much light is good for plants unless we only give them a second of light per day. We should be using umol/area/second-DLI, e.g., PPFD-DLI. And while on this topic, we should not use lumens or lux anyway, they are not for plants, we should use at least umol as PPF and as density with area figured in.
FWIW, here is something I wrote last week about ideal PPFD for cannabis adjusted to a natural diurnal bell-curve of PPFD found in nature:
"Control red to far-red light ratio to limit stretching"
https://www.icmag.com/ic/showthread.php?t=194053
I 100% agree.
I think people use light on 24/7 because they want to (unwittingly) grow less healthy plants; plants that do not have as high of a rate of photosynthesis and rate of growth as plants using proper diurnal (daylength) time, ex. 20 hours max. Plants use night time even in veg to carry out "light independent reactions" (formally termed "dark reactions") such as calvin cycle, circadian rhythm, etc.
Plants grow the most during the night and very early morning hours...by far.
That said, plants can do without a night time, but it's not a great idea.
Not using a night hinders most plants and shows how much cannabis book authors do not understand plant physiology and photobiology. It's really a shame that the likes of Mel Frank, Ed Rosenthall, Jorge Cervanties, etc., perpetuate the incorrect claims that plants do fine when they don't have night. That claim is total BS in terms of rate of photosynthesis, rate of growth, level of plant stress, calvin cycle, circadian rhythm etc., etc.
Plants need night time for the best growth. Plants can grow without a night but they have reduced rate of photosynthesis, reduced rate of growth, reduced carbon assimilate and partitioning, etc., etc., et al.
Also, Ca is transported within plant (xylem) most efficiently during the night IIRC.
Another issue with providing light 24/7 is "photoinhibition" of plants. The problem is the "Daily Light Integral" (DLI), which is the total amount of light (i.e. photons within PAR range) that irradiates the plant per day (as moles/area/day). Too much DLI is just as bad as too much light (as a single instance measurement with Lux, PPFD (umol), etc) in terms of hindering the plant's biological process. Namely by reducing stomatal conductance that in turn reduces the rate of photosynthesis, Co2 fixation, calcium and boron movement into roots, etc.
DLI is a very important factor and one that is lost on most people, sadly. Lumens, lux, umol (ex as PPDF; Photosynthetic Photon Flux Density), etc., are single instance measurements of light. However, we need to consider the sum of light over the whole day, not just for a second. In other words, we should not be using lumens, lux, PPF (umol/second), umol/area/second, etc., to judge how much light is good for plants unless we only give them a second of light per day. We should be using umol/area/second-DLI, e.g., PPFD-DLI. And while on this topic, we should not use lumens or lux anyway, they are not for plants, we should use at least umol as PPF and as density with area figured in.
FWIW, here is something I wrote last week about ideal PPFD for cannabis adjusted to a natural diurnal bell-curve of PPFD found in nature:
"Control red to far-red light ratio to limit stretching"
https://www.icmag.com/ic/showthread.php?t=194053
addendum:
I have tested 24/7 of light when I was new to growing over 15 years ago due to book by so called cannabis gurus. I have also tested it a few years ago. The thing most people don't realize is you can't just look at the plants to judge if 24/7 is better than 16/8 or 17/7. You need to quantify the rate of photosynthesis, rate of Co2 fixation, etc. I find it odd that only at cannabis forums and books would such a silly notion be promoted.
I sickens me how little science is used by cannabis gurus, and because of their status other people assume they are correct, even tho they are not, and those other people perpetuate the incorrect info as is happening in this thread.
@ all:
Either trust me, or study plant photobiology and plant physiology to come to the same conclusion that I have posted: C3 plants need night to grow the best.
More than 18 hours of light a day can be too long of day; over 20 hours is definitely too long. This topic has been studied ad nauseum by plant physiologists and plant scientists of other fields.
I have tested 24/7 of light when I was new to growing over 15 years ago due to book by so called cannabis gurus. I have also tested it a few years ago. The thing most people don't realize is you can't just look at the plants to judge if 24/7 is better than 16/8 or 17/7. You need to quantify the rate of photosynthesis, rate of Co2 fixation, etc. I find it odd that only at cannabis forums and books would such a silly notion be promoted.
I sickens me how little science is used by cannabis gurus, and because of their status other people assume they are correct, even tho they are not, and those other people perpetuate the incorrect info as is happening in this thread.
@ all:
Either trust me, or study plant photobiology and plant physiology to come to the same conclusion that I have posted: C3 plants need night to grow the best.
More than 18 hours of light a day can be too long of day; over 20 hours is definitely too long. This topic has been studied ad nauseum by plant physiologists and plant scientists of other fields.
I'm no botanist, but I did an educational project a few years back that involved research into growing plants in space as a biological life-support system -- to produce food and oxygen, scrub CO2, and purify water. What the scientists told me was that some plants need a dark cycle and some don't. For example, wheat can be grown without a dark cycle, but soybeans cannot. Depends on the plant.
Obviously cannabis does not need a dark cycle, as many growers use 24/0. However, I saw some data (here?) that showed growth (of cannabis) increases with a longer light cycle, but only up to a point. I believe the maximum growth was found with 20/4. Beyond that, additional light makes no difference.
Obviously cannabis does not need a dark cycle, as many growers use 24/0. However, I saw some data (here?) that showed growth (of cannabis) increases with a longer light cycle, but only up to a point. I believe the maximum growth was found with 20/4. Beyond that, additional light makes no difference.
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H
Hoover_lungz
Ive been using 18/6 for vege for over 10yrs now and i have switched to 24hr vege for last 3 month and have noticed my plants growing much rapidly and bushier. I make sure i put them into 18/6hrs for 1 week before putting them into flwering.
I think an important issue is being overlooked: Daily Light Integral (DLI)
For example, a grower can provide the same, or more, light in 18 hours than 24 hours depending upon irradiance over the whole day, i.e. DLI. The sum of light over the whole day (DLI) is very important and allows a grower to provide the same amount of light (photons) in a shorter time frame if the grower so chooses, as long as the grower doesn't exceed peak level of PPFD for cannabis: 1,500-1,600 PPFD.
Calculating DLI is uber easy, but out of scope of this thread I think.
The hours per day isn't all that important as long as it greater than ~6 (in terms of plant health) or greater than ~10-12 hours (in terms of far-red phytochrome; a la flowing); if a grower is providing sufficient irradiance as DLI and does not exceed peak levels of light as a single measurement. If a grower exceeds peak level of light (which leads to excessive DLI) they risk light saturation which leads to ills I wrote about: photoinhibition, photorespiration, greatly reduced stomatal conductance, etc.
For example, a grower can provide the same, or more, light in 18 hours than 24 hours depending upon irradiance over the whole day, i.e. DLI. The sum of light over the whole day (DLI) is very important and allows a grower to provide the same amount of light (photons) in a shorter time frame if the grower so chooses, as long as the grower doesn't exceed peak level of PPFD for cannabis: 1,500-1,600 PPFD.
Calculating DLI is uber easy, but out of scope of this thread I think.
The hours per day isn't all that important as long as it greater than ~6 (in terms of plant health) or greater than ~10-12 hours (in terms of far-red phytochrome; a la flowing); if a grower is providing sufficient irradiance as DLI and does not exceed peak levels of light as a single measurement. If a grower exceeds peak level of light (which leads to excessive DLI) they risk light saturation which leads to ills I wrote about: photoinhibition, photorespiration, greatly reduced stomatal conductance, etc.
We tend to for the most part, always do 16/8 but with 24hr fluoros on all the time. It's funny cause when the lights are off but the room lights are still on you will see the plants take their night rest and drop their guards and when the lights come on, they perk right back up.
We do clones and everything this way and never had problems, with semi large plant numbers as well and prefer it because it let's your schedule be more flexible and not dictated around the hours of darkness. Lots of different ways to get it done, just gotta find what works best for you.
We do clones and everything this way and never had problems, with semi large plant numbers as well and prefer it because it let's your schedule be more flexible and not dictated around the hours of darkness. Lots of different ways to get it done, just gotta find what works best for you.
thats why there auto flower o.o
A dark period is natural. Just as outside there is no 24hr light period. I personally think plants grown without a dark period are missing and essential part of life. GOD did not make the dark hours for nothing. Just my
Have you ever seen things grown in Alaska in summer with NO darkness? HUGE yields! In a month, they get more than a whole season in the states. How, if "dark" is so important?
God didn't make the dark at night...just like eclipses aren't a dragon eating the sun...wake up...religion is control...not an explanation.
I'm not ragging on you...just setting things straight.
<grin> It's not just you.
FWIW, I veg 20/4. I ran 24/0 for years, experimented with 18/6, and finally settled on 20/4. YMMV.
Simon
If you read the safety sheet most MH lamps recommend that at least once a week they are to be shut off and allowed to cool. As far as the plant goes feel free to experiment you are not likely to harm anything and if you interrupt the dark cycle in veg its not a problem unlike when in flower. trying different things makes you a better and more experienced grower if you just do the same thing time after time you end up in a rut and your garden suffers.
I used to live in alaska and yes during the summer it is light ALMOST 24hrs a day. in the winter its opposite and dark at 1pm. There is still darkness there just not much. Who said anything about GOD making dark at night..all I said was GOD made the dark for a reason. Nothing more or less! This thread is about plants grown under 24hrs of light and why. I have my opinion and u have yours. Let's agree to disagree and call it a day!
Freedom Grows
Member
Im vegging in 18/6 but thinking of going 20/4 next grow, more light is good right 
But i also think some dark hours are important for the plant, i know its no real problem vegging under 24 hours of light, but it just doesn't seem nice to the plant you know
But i also think some dark hours are important for the plant, i know its no real problem vegging under 24 hours of light, but it just doesn't seem nice to the plant you know
