24hr. verses 18hr. lights - Benefits?????

[Lanietheberner]

We have been running a 18hr lighting cycle in the veg stage and a number of others in our co-op are running their lights for a full 24 hrs. No one has been able to explain the benefits (other than a higher power bill...LOL).

Can someone enlighten me on the benefits and issues with this?

Thanks from the Northern California Foothills for any helpful info!!!!:thumbsup:

[jamstigator]

The benefit to running lights 24 hours a day during veg is simple: faster, more vibrant growth over the same amount of time. The only reasons to use anything other than constant lighting during veg is if you WANT to slow down growth (because your flower box/room won't be ready for a while), or because your ventilation is inadequate to handle the heat without a cooling off period.

So, if you don't have good ventilation, or if you'd rather grow a bit more slowly for some reason, use 18/6, or 16/8. If you do have good ventilation and the heat isn't a problem running the lights constantly, and you want faster and more vibrant growth, keep the lights on all the time. You don't really spend more money, because you can get the same size plants in 24 days of 24/0 lighting as you can in 32 days of 18/6 lighting. You spend the same amount either way, you just spread the electric bill out over a longer period of time by using less light per day (but for more days).

[Abattoir Dream]

/\ hes a smartypants ;)

[LIP]

Actually, i'd say 18/6 is better for the plants during the veg stage. It gives the plant a 6 hour re-cooperation period, that it NEEDS, as this is roughly what it would get in natural conditions. It alows the plant to build energy, so when the light are on it can concentrate. The plant needs some amount of dark for correct photosynthesis.

[jamstigator]

Well, I've seen people say that, Lip. And then the people who write the books about growing cannabis differ. The best book I have, the one that has been the most accurate and useful (The Cannabis Grow Bible), says 24/0 provides faster growth. Because I am a skeptic and happen to have two exactly identical cabinets (one for mothers, one for clones, but exactly the same), I tested this so that rather than relying on what people SAY, I have seen with my own two eyes all I need to know.

My experiment bears out what the book told me: 24/0 promotes faster and more vigorous growth. My 24/0 plants after a month were noticeably larger and more lush than the 18/6 plants. I occasionally still use 18/6, when I know my flowering cabinet won't be ready for six weeks or whatever.

I will quote from the book though. If you do the experiment yourself, you'll see that what the author says here is true:

"Cannabis is a light demanding plant. Professional growers keep the light on their plants using the 24/0 photoperiod for this reason. Plants that grow under 24/0 flourish and do not need a quantity of darkness in order to rest and perform photosynthesis properly. Plants that are grown in optimal conditions under the 24/0 light regime grow vigorously and the benefits of a 24/0 photperiod can be seen in the results. More nodes are formed, more branches are created, leaf numbers increase, the plant is growing at its finest.

Some growers opt to use 18/6 as their photoperiod. This is an 18 hours of light, six hours of darkness light regime. Under these conditions the plant will grow quite naturally but not as vigorously as the 24/0 photperiod.

The 18/6 photoperiod expels 3/4 the amount of light that a 24/0 photoperiod does. Although this does not mean that a plant produces 1/4 less leaves, branches and nodes under the 18/6 photoperiod, it certainly does show the correlation between light and cannabis growth. As we have said already, cannabis is a light demanding plant. There are no problems associated with 24/0 and although some have attributed cannabis sexual dysfunction (the hermaphrodite condition) to the 18/6 photperiod these problems are actually the result of heat stress.

A 24/0 photperiod requires that your grow room temperature be kept well monitored. The 18/6 option is cheaper to run. You use a quarter less electricity and this will have an impact on your electricity bill. Also the 18/6 photperiod will generally extend the bulb's lifespan. During the 6 hours of darkness the grow room is allowed to cool down for this period, but a well-maintained good grow room setup should not require a cooling down period."

My experiment bears out what the author said in the above paragraphs. If you somehow get larger/better plants under 18/6, the reason must be that your ventilation system isn't adequate to handle a 24/0 photoperiod because of heat buildup. On the other hand, if you do have good temperature control, then there is little reason not to just keep the lights on constantly. Yes, it's cheaper to operate 18/6 on a per-day basis, but to achieve the same size plants as you would get under 24/0, you'd need to veg for more days, which means more electricity, so it balances out cost-wise.

Don't listen to me though. Instead, I encourage you to do the same experiment. It's better to know things from experience rather than being told them. If you have two identical cabinets, and have your temps under control such that letting the lights run constantly does not result in too much heat, then do the experiment yourself, and you will see with your own two eyes what I have seen with mine.

[jamstigator]

By the way, the author made an error in his writing. Where he says:

"There are no problems associated with 24/0 and although some have attributed cannabis sexual dysfunction (the hermaphrodite condition) to the 18/6 photoperiod these problems are actually the result of heat stress."

I believe what he meant was:

"There are no problems associated with 24/0 and although some have attributed cannabis sexual dysfunction (the hermaphrodite condition) to the 24/0 photoperiod these problems are actually the result of heat stress."

Heh, he should hire me to edit his book and clean up the errors; it does need better proofreading. But he's a stoner, so I forgive him. ;)

[checkmark9]

it does need better proofreading. But he's a stoner, so I forgive him. ;)

Amen, we need more people to forgive stones about little mistakes.

[xcrispi]

hey folks ,
i choose 18/6 or even 20/4 . i have found over the years that both my bulbs and my ballasts last longer when given a break . might be an extra week or so in cycle time but this isn't a prob. for me .
peace
more than 1 way to skin a cat