What are Light Cycles and How Do I use Them?

[SmokeyMacPot]

The amount of time your garden should be exposed to lighting depends on what 'cycle' your garden is in:

The 'Vegetative Cycle' of your garden starts with the sprout of the seedlings and can be continued indefinitely. In the veg cycle your garden will require a minimum of 16-18 hours of light and 6-8 hours of darkness daily. Since a given amount of light can only do so much, equal production can be realized in a smaller space with less plants, where the light is concentrated and the plants can grow more efficiently. Using more light helps additional co2 uptake.

Since a plant can be kept in the 'Veg cycle' indefinately, many growers cultivate 'Mother' plants. This plant is used for clone starts and never produces buds, only new growth.

The 'Flower Cycle' or 'Bud cycle' is typically equal amounts of light and dark, 12 hours on, 12 hours off or 12/12. This produces a change in the plants metabolism simulating Fall, shorter days....less light.

This is the cycle that the plants will show their sex. Usually, you'll be able to determine the sex within the first 2 weeks of 12/12. By the 3rd week most plants have developed healthy bud sites or pollen sacks.
The plants will continue on the 12/12 cycle until harvest.

When someone 'Re-vegges' a plant that has been in the flower cycle, they're switching the light cycle back to 18/6 to stimulate new vegetative growth.

Author: Mr.Zog

[Nerdly1]

My comments are meant for "light tight" indoor grows only. Somewhere in the myriad of threads I read about running your lights in the coolest part of the day. This gave me a reason for "which" 12 hours of the day I'd run my 400 w. HPS.
Example:
With summer coming soon, I'm training my flowering plants to a 12/12 grow cycle, starting at 9:00 pm each evening till 9:00 am each morning. I figure I won't be fighting so much heat as in the daytime.
Is this some obvious fact I've just become aware of or does everyone run their light cycles this way? Naturally 18/6 & 12/12 light cycles are normal, but I have been running them according to my daily schedule. Changing the schedule just seems logical and more economical.

[420NV]

I think Gadgetman is on to something here. I believe my plant went male simply because of the temp. I can't think of any other reason. We too have had our plants on our shedule, however, this grow was during the summer, and things went differently this time. I'm starting a new grow, and going to have the lamps running during the cooler night hours and see what happens this time.

[metalhearts]

im a first time grower and i started out with a 24 hr light on my seeds and im on the 4th day. i was wondering if i should switch to 18 hrs a day or just stick to 24 since thats what i started with?

[420NV]

i did 24 hr. light til they sprouted, then went to 16/8, then 12/12 during flowering.

[gazan114]

i am also new and what i am trying is 24 for 2 day and 23.5/.5 for 2 days and so on and so on untill the 50th day when it is 12/12 and leave it at 12/12 good idea or just simply idiotic?

[420NV]

Never heard of this. why would you do this?
"plants take advantage of dark times to ramp up the manufacture of plant sugars that their roots store for use in making new cells for growth. It's kind of like a factory where the raw materials are being unloaded all day (i.e. water from the soil, light from above and carbon dioxide from the air), and then when the truck� leave, the workers have time to actually produce the goods."
I got this quote from a plant growing sight. you should google why plants need darkness to fully understand the necessity of darkness for your babies.

[RedmybudsRed]

Plants need dark to build up Florins (hormones the plant uses to flower)
I've only on my 1st grow but from experience & all my research, I think the safest bet is to: 24 hrs first 2 weeks max, then drop to 18/6

[redfox30]

Light schedules are not complicated, so don't make them just that, the three main schedules are as follows

a) 24/0 or sometimes known as 24/7.......this refers to the light being on for 24 hours a day / or 24 hours a day for 7 days of the week for the desired number of weeks that plant needs to mature enough to be flowered,or to your desire, this is known as the "vegatative stage."

b) 18/6 this means on for 18 hours and off for the remaining 6, and as above till the plant has matured enough to be flowered, or the height you desire, this is also a vegatative light schedule.

c) 12/12 this means on for 12 hours and off for 12 hours, this scheduule is used to force the plant to flower, by mimicing the on-set of winter, the female plant will flower in the hope of receiving pollen from the male plant, and produce seeds....hence not having any males polllinate your females means you have "sensemilla" or seedless buds,this schedule is used in the "flowering" phase.