How To Grow Cannabis From Seed Under 12-12 Lighting
Force flowering marijuana from seed can provide excellent quality, resinous flowers, all the while saving space, time, and money. For those with space constraints, it is a win-win!
Do you want to go from seed to bud quicker and cheaper? A faster, space saving and economical way to grow is the no veg, seed to flower, 12-12 light cycle method.
Growing with a 12-12 photoperiod is a solution to space and resource problems. This method eliminates the vegetation phase of growth and forces the plant to go straight into flower from a seedling. Yields are lower than that of a regularly grown cannabis plant, but results are obtained much faster, with a few advantages.
The 12-12 lighting technique makes the grow cycle 7-9 weeks in general, rather than the much longer time needed when giving plants a vegetative phase. For the space constrained, and those willing to experiment and give it ago, it can be a dream come true.
WHAT IS 12-12?
12-12 simply refers to the hours of light and darkness a cannabis plant is exposed to – 12 of each. Normally, a cannabis plant is exposed to an 18-6 light cycle. This tells the cannabis plant conditions are good for growth, and it focuses on building up size and foliage. When light cycle is changed to 12-12 (either naturally or through human intervention), it tells the cannabis the seasons are changing, and it is time to flower. By forcing a 12-12 light period from the start, the cannabis plant goes directly into flowering, in a bid to reproduce. You are essentially tricking the plant into thinking the growing season is coming to an end, so it needs to produce flowers ASAP.
Growing 12-12 is as simple as changing the timing on your light cycles, giving your plants equal amounts of day and night right from when they sprout. The plants will look different to a cannabis plant that goes through vegetative growth. Photosensitive hormones in cannabis make the highest point the largest cola. This method all but guarantees only main bud growth on every small plant. Essentially you will be growing a cola with a few short, budded side branches – with the plant basically being a bud in itself. Be sure to stake your plants.
Everything to which you would pay attention in a normal grow remains unchanged and are still just as important. pH and water quality, nutrient mixing, pest control, grow medium conditions, EC and ppm all still play their major roles in the dankness and weight of your finished product.
Growing this way still requires all the knowledge that would be needed to flower plants with any other method, and maintenance routines still remain unchanged. After diluted nutrients, while still young, treat your plants as you would during a normal bud cycle. However, flush more often, every ten days at most, so as to avoid salt build-up in the smaller pots.
Done with expert practice and a willing strain of cannabis seeds, it is not unknown to produce 1 gram of ganja per watt of lighting. That’s an impressive 250g in 7-9 weeks for a 250W light in a small cupboard!
- Lights have full penetration to the floor. Keep an eye on the soil wetness as lights will dry the medium quicker than if protected by a canopy
- This method is fast. 7-9 weeks on average
- Less drama trimming as there are far less sugar leaves to deal with
- Plants are easier to handle for maintenance
- Can grow in tiny areas
- Save wear and tear on moving components
- Save money
Plants with less side branching and canopy spread need less space between them, increasing efficiency. As an example: 1x 15-litre pot produces one plant with a large volume and difficult maintenance issues in a cramped space. 4x 3.5-litre pots in the same sized space can produce just as much dried material with the benefit of being easier to rotate, so the whole plant gets 360-degree light. The entire crop is less hassle during maintenance as each plant is 100% accessible and physically easier to move about. There is no need for a separate sprouting and veg space or time wasted on 18-6 vegetation. The seeds can be sprouted under the 12-12 growing lights providing continual flowering plants.
There is a lesser demand for resources across the boards.
You will experience only half the water consumption with less moisture loss due to evaporation, and a third less nutrients are used. CO₂ and electricity use including most peripherals are reduced by a staggering 650 grow hours annually.
Taking hours to accomplish, tipping, fimming, branch control, and mainlining are now unnecessary freeing up your most precious resource, time.
Always be sure to re-sterilize your grow space after each crop.
Keep a keen eye out for moulds and mildews as the grow space will be getting less light with more moulding opportunity in warm dark corners and creases.
There are some haters of this method, but many love it. Those who hate on it often have not actually tried it. It is all about giving it a go and seeing what works for you. Even if you decide against it after trying it, it all helps expand your knowledge as a grower.
Some sativas will still stretch to 1.2 metres using this method, so species selection right at the very start is key. Indicas are the obvious choice for maximum space saving. They are generally smaller, and 12-12 will keep them very manageable. You will enjoy small pots full of colas, like a miniature stinky forest. Buds grown this way are indistinguishable from vegetated plants in flavour and effects, and at the end of the day, getting buds in the jar quicker and more often is a good thing right?
How to force cannabis to flower from seed for quick, resinous yields using a 12-12 light cycle.
Cannabis Light Periods – What do I need to know about marijuana light cycles? (length of sunlight hours each day)
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…
Cannbis plants have two life stages:
1.) Vegetative – Seedling or clone leads to Vegetative Stage
- Give 18-24 hours of light a day (indoors)
- Cannabis grows only stems and leaves
2.) Flowering – Flowering (Budding) Stage leads to Harvest
- Give at least 12 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 in Spring when the 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.
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, most cannabis plants will show the first signs of their gender (they either are a female plant which starts growing buds, YAY! or they are a male plant which start 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 plants to produce seeds and less buds.
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 an internal process that allows them to detect 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 approaching the 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 cyle).
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 gets 12 hours of light a day and 12 hours of total darkness.
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 to flip their 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 guide for 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 effects 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.
Cannabis Light Periods – What do I need to know about marijuana light cycles? (length of sunlight hours each day) If you’re growing a cannabis plant grown from a random seed (“bagseed”), unless