by Nebula Haze
If you’re growing a cannabis plant grown from a random seed (“bagseed”) unless you somehow have an auto-flowering seed, you will need to understand about cannabis life stages and how they are affected by light periods.
If you don’t understand light periods, your plant may never start making buds!The light schedule experienced by your plant will actually change its life stage. Learn more…
Cannabis plants have two life stages:
1.) Vegetative–Seedling or cloneleads toVegetative Stage
- Give 18-24 hours of light a day (indoors)
- Cannabis grows only stems and leaves
2.) Flowering–Flowering (Budding)Stageleads toHarvest
- Give at least12 hours of uninterrupted dark each day (short days)
- Cannabis starts growing flowers/buds
The first stage, “Vegetative” begins when marijuana plants first sprout, at the beginning of their life.
Most indoor growers give their cannabis plants 18-24 hours of light a day during the vegetative stage.The exact number of hours needed to keep a plant in the vegetative stage is dependent on the strain, but 18+ hours/day will keep basically all cannabis plants in the vegetative stage.
Outdoor growers plant their seeds inSpringwhenthe days are naturally longer. In the wild, cannabis seeds naturally germinate in the Spring.
For an indoor grower, when a plant is about half the final size you want it to be, you should change it over to the “Flowering” stage. This is the stage when your plant starts growing buds.
Learn more about the flowering (budding) phase
You do this by changing your light so that it only shines for 12 hours a day, and the other 12 hours a day your marijuana plants are kept in TOTAL darkness.
After 2-3 weeks of the 12-12 light schedule,mostcannabis plants will show the first signs of their gender(they either are a female plant whichstarts growing buds, YAY! or they are a male plant whichstart growing balls/pollen sacs, NO!).
Boy cannabis plants don’t give you any usable amounts of THC, so most growers toss them on sight. These male plants can also impregnate (pollinate)your female plants, which causes your female plantsto produce seeds and lessbuds.
Learn more about male vs female cannabis plants
So unless you’re planning on breeding, it’s important that most growers destroy male plants as soon as you notice them growing grape-like balls where their buds would normally be.
Unfortunately, about 50% of all regular (unfeminized)cannabis seeds are male (though this varies from strain to strain, and from environment to environment). Fortunately for small growers, you can purchase feminized (all-female) seeds so you don’t have to worry about male plants if you don’t want to. Learn more about buying seeds.
When does a cannabis plant start budding?
Marijuana plants have aninternal process that allows them todetect how long they receive darkness each night. This is because they are a “photo-period” plant, specifically a “short-day” plant which means these plants start making flowers/buds when days start getting short.
In the wild, as the days get shorter and nights grow longer, a marijuana plant “realizes” that winter is coming and will start budding/flowering. It “knows” it’s approachingthe end of its life cycle so it frantically starts making buds in time before winter.
When growing marijuana outdoors, a grower doesn’t need to do anything to induce flowering because the sun will take care of things on its own. It’s just important to make sure that there are no lights shining on your plants during their night period (which will disrupt their dark cycle).
However,when growing weed indoors, a marijuana gardener will have to fool their plants into “thinking” winter is coming to induce flowering and kickstart the creation of buds.
This is done by changing the plant’s light schedule to 12-12, where the weed plants get 12 hours of light a day and 12 hours of total darkness.
Marijuana Flowering Stage Timeline
You’ll get the best results if the start and end time for the light is exactly the same each day, which is why most growers end up getting a timer tofliptheir lights on and off, like an automatice light switch.
I tend to set my timer to shine line from 8pm-8am. This gives me time to check on my plants at night when the lights first come on, and I can also check them quickly in the morning before I go to work. It also keeps things cooler since the lights go on at night.
But ANY 12 hour period will work, as long as you remain consistent.
Check out my cannabis grow light guidefor more info about picking out suitable lights!
Photoperiod-dependent strains vs. auto-flowering strains
So all strains of cannabis that respond to light in this way (where the light period affects what stage they’re in) are called “Photoperiod dependent” strains.
“Auto-flowering” marijuana strains pretty much ignore how much light they get each day. Generally, you don’t run into these unless you buy them, particularly from a cannabis seed bank.
Jump to…
The Basics of Growing Weed
10-Step Quick Start Grow Guide
Teach Me About Cannabis Nutrients
7 Steps to Fixing 99% of Growing Problems
