Light Cycles for Growing Cannabis, Fully Explained


light cycles for growing cannabis by

Percy's grow room a cannabis plants will

grow differently according to how much

light it gets daytime compared to how

much darkness it gets nighttime there

are many different light cycles for

growing cannabis indoors each have their

own pros and cons in this video we will

discuss different light cycles for

growing cannabis when to use them and

why this will help you understand how to

grow cannabis and it's or more what are

light cycles light cycles are the amount

of light versus the amount of darkness a

plant receives a cannabis plant will

start to grow in the spring flower

throughout summer and be harvested in

the autumn throughout the year it will

receive a different amount of light

depending on what season it is when you

use light cycles indoors you're trying

to imitate the length of day for

springtime or summertime this will keep

a plant in veg simulating springtime

growth or in flower simulating summer

growth to understand light cycles for

growing cannabis you should understand

how a plant grows in its natural habitat

outdoors cannabis light cycles outdoors

as the year goes from spring into summer

and then to autumn the days get longer

and then shorter unless you're growing

near the equator plants can detect the

changes in the amount of light they

receive and this tells them what season

they are in spring equinox sometime

around March 20th in the Northern

Hemisphere or September 23rd in the

southern hemisphere the days begin to

get longer and we head into spring this

is when a cannabis seed will germinate

and begin its lifecycle outdoors as the

days get longer the plant will grow more

and more and continue into its

vegetative stage until the days start to

become shorter this happens shortly

after the summer solstice summer

solstice the summer solstice is when the

days reach their longest

up until now the plant has grown in its

vegetative state

this is midsummer and the plants will

soon prepare themselves for flowering it

would depend on what strain you're

growing but the flowers will start to

grow when the plants get around 14 hours

of daylight and 10 hours of darkness

when the flowering stage begins it will

continue for around 8 to 14 weeks until

it is harvested in late autumn autumn

equinox autumn equinoxes September the

days are 12 hours long and the night is

also 12 hours long this is when a

cannabis plants will be in the flowering

stage by now the plant should already be

showing small flowers when a plant

starts to grow its flowers each strain

dependent and so is harvest time sativa

dominant strains will flower for longer

than indica dominant strains and may

need to be harvested later a cannabis

plant will flower for anything from 8 to

16 weeks but when growing outdoors you

must harvest the pram before frost sets

in and the colder weather of winter

starts winter solstice at this point

your plant should already have been

harvested this is the height of winter

when the nights are longer than the days

in its natural habitat a cannabis plant

cannot survive these conditions and

would have died already any seeds made

by the female plants will be laying

under the surface of the ground waiting

for conditions to improve when

springtime comes again and the climate

starts to get warmer the seeds will

germinate around the spring equinox and

the whole cycle begins again this is how

a cannabis plant uses light cycles

naturally in the wild when you grow

cannabis indoors you have to simulate

the length of day and night to induce

certain stages of the cannabis plants

life cycle growing around the equator

the days and nights around the equator

are always around the same length 12

hours day and twelve hours night a

cannabis plant can grow fine under 12 12

but it will not stay in its vegetative

state for long about four weeks after

germination a cannabis plant will reach

maturity and it will be ready to grow

flowers before this the

is not ready to grow buds and even if it

is on 1212

it will only veg you can grow cannabis

using twelve hours of light and 12 hours

of darkness from seed just like a plant

grown at the equator but this will not

speed the grow up you still have to wait

about four or five weeks after

germination before the flowering cycle

begins light cycles for growing indoors

the idea of using light cycles to grow

cannabis indoors is pretty much trying

to simulate the Sun at certain times of

the year this is not only done with the

length of day and night but also what

color light the plants get

in springtime the light will be slightly

more into the blue spectrum and during

summer it will be a lot more red

different bulbs can be used at different

stages of growth to imitate this you

have more control over lighting when

growing cannabis indoors and can control

the length of day and night by using a

timer timers for cannabis grow lights

grow lights are heavy-duty and they use

a lot of power because of this you need

to be sure you use the correct timer for

your lighting rig you have to be safe

with your equipment if you use a timer

that isn't designed for a heavy load it

may short-circuit at the very least the

timer could break and the light cycle

your plants are used to will be suddenly

changed and this will cause them stress

if your plant is in flower and there is

an irregular light cycle it can cause it

to hermie you must use reliable safe

equipment you can't put a price on peace

of mind 24 zero lights on all day a

cannabis plant can be grown under 24

hours of light with no dark period this

light cycle tends to be used on

seedlings or cuttings in the early

stages of growth some growers will grow

autoflowering cannabis plants under 24

hours of light but of course when

growing indoors more hours of light

means more energy bills it is not clear

whether the extra energy turns into

extra yield 24 lights on for 20 hours a

light cycle of twenty hours lights and

four hours darkness tends to be used for

seedlings and cuttings or auto flowering

plants this is preferred over 24 hours

of light as it gives the plant some time

to rest and it reduces the energy bills

a little when you are growing indoors

you are trying to imitate a natural

environment all plants will receive some

hours of darkness so 24 is usually the

most amount of light a grower will give

to a plant 18 6 lights on for 18 hours

18 6 is the most common light cycle for

growing cannabis it is used to vegetate

photo period cannabis plants or grow

autoflowering cannabis plants for their

life cycle by keeping a photo period

cannabis plants under 18 hours of light

and six hours of darkness it will stay

in the vegetative stage a plan can be

kept in this state for years and this is

how mother plants are kept a cannabis

plant will not start to flower until it

receives at least ten hours of darkness

and 14 hours of light but this is strain

dependent 14 10 lights on for 14 hours

some strains of cannabis may begin to

flower with 14 hours of light and 10

hours of darkness this is risky though

if the cannabis plant gets confused

about its light cycle during the

flowering period it can Reeve edge or


so when Scheuer a plant goes into flower

and has no side effects most cannabis

plants will be flowered under 12:12


an equal amount of light and dark 12:12

is the light cycle used to induce

flowering in a cannabis plant when the

days and nights are the same length of

time a cannabis plant will release a

hormone that triggers the flowering

process this hormone takes a few days to

a week to build up and then you will see

flowers starting to form the night cycle

must be undisturbed with no light

interrupting it at all make sure that

any equipment with lights on or any

light leaks coming into the grow room

are sealed

disturbing the night cycle can force the

plant to revenge or hermaphrodite and

grow seeds the most popular light cycles

for growing cannabis are 1864 veg and 12

trial for flower just sticking with

these two light cycles will be fine

photo period cannabis plants photo

period cannabis plants are plants that

react to light cycles for example plants

that were vegetate under 18 6 but not

flower until they are under 12 12 a

photo period cannabis plants will not

reach maturity until it is around four

to five weeks from seed even if a plant

is grown under 12 12 from seed flowers

will not start to show until it is

mature it is always best to veg a photo

period cannabis plants under 18 6

for at least four weeks before flipping

to flower you can veg a photo period

cannabis plants for as long as you need

to by growing one plant and extending

the veg period by a couple of weeks you

can achieve the same yield as 10 small

plants night cycle during flower when

growing photo period cannabis plants it

is vital that the hours of darkness are

undisturbed even a small LED light on a

piece of equipment is enough to stop

your plant from flowering if you have

light leaks you risk three things one

your plants were not flower when you

want them to to your plants may revert

back to the vegetative stage 3 your

plants will hermaphrodites and produce

seeds before you change your light cycle

to 1212 you should make sure your tent

or grow room is fully light proof and

free from any lights on the equipment

you can do this by getting into your

grow room with the lights off and all

doors and vents closed wait a few

minutes for your eyes to adjust to the

darkness and you will see any lights

coming in CL up light leaks with tape or

direct intake vents to draw air from a

dark place if you have any equipments in

the grow room that does give off light

remove it or cover the light with tape

to stop it leaking out also flowering

cannabis plants autoflowering cannabis

plants are a little different

they will flower under any light cycle

12 12 or 24 hours of light a day this is

a great advantage as you can grow

autoflowering cannabis plants alongside

vegetating plants or have many autos in

the same room at different stages of

growth light leaks can still cause

problems with autos and you should still

ensure any dark period you give plants

is fully dark with no light leaks or

irregular exposure to light most growers

will grow autoflowering cannabis plants

under 18 6 for their whole lifecycle

some may even push it to 24 but it is

rare that any one grows autos under 24

hours of light once they are out of the

seedling stage

final notes on light cycles for growing

cannabis choose which light cycle will

work best for you and decide if you are

going to grow autos or photos when you

choose the light cycle you should set

the night time to be over the hottest

part of the day for example if you are

growing in summer the hottest part of

the day will be around midday because

grow lights produce a lot of heat it is

advised to run them at night and turn

them off during the day this will make

it easier to keep temperatures under

control thanks for listening Percy