Learn what it means to give your plants "12-12 from seed" to force them to start making buds early. Curious to the 12-12 from seed technique (for solo cups) and how to apply this method? Learn more on growing 12-12 from seed and yield potential. 12/12 from seed has a big problem. Learn about a better alternative called "Sea of Green" that gives you bigger yields in the same amount of time!
12-12 From Seed – Flowering Plants Early
The term “12-12” means you’re giving your cannabis plants 12 hours of darkness, and 12 hours of light every day. “12-12 from seed” mean you’re giving a cannabis plant a 12-12 light schedule from a very young age to force it to flower early (make buds) while staying small.
Some growers are attracted to the idea of 12-12 from seed, because it means that harvest will come sooner. How long does it take to grow a plant from seed to harvest?
But does the 12-12 from seed technique work to give you a faster harvest, and if so, what are the results?
I have changed cannabis plants over to the flowering stage from seed, but no matter what the light schedule, plants don’t start flowering (making buds) until they are about 3 weeks old. Initiating a 12-12 light schedule at 3 weeks old from seed is as early as I’d recommend for this technique, if you choose to use it.
“12-12 From Seed” is a misnomer if you’re trying to force your cannabis to flower early – 3 weeks from seed is the earliest time a plant can start flowering after the switch to 12-12
Make sure to let your young marijuana plants get a minimum 2-3 weeks in the vegetative stage before changing them over to flowering. Your plants will be healthier and will start flowering at the same time as if you started 12-12 from when they first sprout.
Giving a 12-12 shedule when a cannabis plant is younger than that will not work to make the cannabis start flowering – a cannabis plant will only grow vegetatively for the first few weeks of life, and giving them less light will only cause them to grow more slowly.
Some strains of cannabis will naturally start flowering after about 3 weeks, and you don’t need to do anything with light schedules to cause that to happen. These strains are known as “autoflowering” or “Ruderalis” strains.
Many Growers Who Want To Force Cannabis Plants to Flower at a Young Age May Be Interested in Auto-Flowering Strains – No Need for 12-12 and Often Much Better Yields!
I have grown a few plants from seed to harvest just in a solo cup container. I was able to do this by flowering a plant from a young age – giving the plant 12-12 lighting when it was only 3 weeks old (pictured here).
These solo cup plants were able to survive their entire lives in a small container. I wouldn’t recommend a solo cup because they tip over easily, and plants are prone to nutrient and root problems once the flowering stage begins (the root space is just way too small, even when doing 12-12 from seed or using an auto-flowering stage).
But it’s possible.
The downsides… When your cannabis is kept in a too-small container, you will notice that you have to water your plant much more often than if you kept your plant in a big pot. As time goes on, plants are also more likely to suffer from nutrient problems and root problems because the roots aren’t being give enough room to spread out. When plants become root-bound this way, there’s not much you can do about this besides transplanting your plants into a bigger container.
While I wouldn’t recommend 12-12 from seed, and no longer ever use this technique myself, there are growers who are going to do it anyway.
For those growers who still want to use 12-12 from seed despite the warnings here…
If you are set on keeping potted cannabis plants in small containers for their whole lives, the smallest container you should try is a 1-gallon or 2-gallon container, like the pots pictured here.
Keeping plants in tiny containers may be important when growing in a very space-limited grow space, such as growing in a space bucket for stealth reasons.
There are powerful cannabis growth control techniques that will also allow you to grow high-producing plants, while keeping them short.
But like this extreme girl to the right (less than a foot tall and grown under CFLs), I’ve experimented starting the plants on 12/12 from seed to keep plants REALLY small.
When forcing your cannabis to flower early, plants will stay small and spend almost all their energy on producing flowers/buds on what few stems they have, instead of growing tall or making more colas/nodes.
Some people say that cannabis that is forced to flower too early will not make any buds, but that’s not true. The plant pictured here produced 0.75 ounces of bud after drying. So while 12-12 from seed may not be optimal, it does work.
The problems I’ve had with forcing cannabis to flower early is that since the plant is much smaller, you get smaller yields, but you’re still basically spending about the same amount of time to grow the plant as if you’d grown it bigger.
Compared to 12-12 from seed, growing an auto-flowering strain will generally give you bigger yields for the time, and will be less trouble
With such small plants, you don’t have the time to train your plant, which gives you much greater control over the final shape and size of your plant, improving yields without adding much time.
The other disadvantage to overly small plants is their inability to recover well from problems: you have fewer leaves as a ‘buffer’ so the plant can’t bounce back when something goes wrong such as a pest attack. In a too-small container, as roots get more root-bound, cannabis plants have a harder time using nutrients efficiently, and may start showing nutrient problems.
Growing extremely tiny marijuana plants is fun, but honestly you’ll get the biggest yields by instead investing a little more time in the vegetative stage to train your plant to grow into the exact shape you want. Or just grow an auto-flowering strain.
Guide to: 12-12 From Seed Technique
With regular and feminized seeds, you need to determine when to end the vegetative phase and make the plants flower. Usually, it can take several weeks. However, you can force your plants to flower a lot earlier than when they are under regular conditions.
By managing how much light cannabis receives, you can begin harvesting as soon as possible. Some people have time and space constraints. Growing 12-12 from seed is beneficial if you experience both of those challenges.
Continue reading if you want to know more about this process.
What Is Growing 12-12 From Seed?
Growing 12-12 from seed means that you would give your seedling 12 hours of light and 12 hours of darkness soon after germination. Usually, cannabis receives an 18/6 cycle during the early stages of life. Switching to a 12-12 schedule initiates the flowering stage.
With equal amounts of light and dark, your young plants would begin flowering right from the start. Some growers grow 12-12 from seed since it is perfect for solo cup growing. The plant’s roots do not need much room to grow, since the vegetative period will be short.
So, a solo cup or another small container can work well. However, you may need to water cannabis a bit more frequently.
One reason you might want to try using a 12-12 light cycle after germination is the shorter cultivation time. Cannabis typically takes 3-4 months to reach harvest. You can enjoy some nice buds sooner than expected.
Trimming becomes less of a hassle as well. You do not need to manage as many sugar leaves compared to when you grow marijuana normally. You can save money on water, nutrients, and energy as well.
Another advantage of growing weed under 12-12 lighting is the space you can save. The plants can grow in smaller containers, and the branches do not extend too far. Not to mention, cannabis plants are easier to move. You can turn them around for the light to reach all the leaves.
Some growers do not grow 12-12 from seed due to a few of the disadvantages. One of the main drawbacks is the reduced size of the plants. The shorter vegetative phase means the plant has less time to mature to its full mass. Still, you can get desirable yields.
You would not be able to do a lot of the training techniques as well. Most of them occur during the vegetative stage, so you would not have enough time to do something like monster cropping. One of your options would be low-stress training.
Expected Yield When Growing 12-12 From Seed
If you are intrigued by growing marijuana with 12-12 lighting, you might wonder how much you can harvest. The yield weight is usually not that hefty, but the lights, strain, and pot size can make a difference.
If you grow a seed in something like a solo cup, the average amount is 3.5 grams. You can get around 14 grams from a plant with a slightly larger pot. Some cannabis growers prefer to use containers of up to a gallon. They can get up to 28 grams for each plant.
However, you can get much more from your crops if you grow them with the SoG method.
How to Grow Cannabis 12-12 From Seed
Growing a cannabis seed with a 12-12 light cycle only has a few steps. They are simple to do, and you do not need much when it comes to equipment. If you decide to use this method to grow weed, what you need to do is:
1. Germinate Seeds
For germination, the seeds need some dampness and a warm environment. There are multiple ways you can go about germinating cannabis seeds. Some growers buy starter cubes since they are convenient.
They contain some micronutrients to encourage the roots to grow. Add some water and wait a few days for the germination process to complete. Instead of a starter cube, you could use a non-porous paper towel instead.
Take a paper towel and make it damp. Then, you would fold it over the seeds and wait around 1-4 days. It is helpful to have a spray bottle around since the paper towel can dry out. You can check periodically to see if the taproot emerged.
Once you see roots, carefully remove the seeds and move on to the next step. For tougher seeds, some growers leave them in a glass of water overnight. You could soak your seeds in water and place any stubborn ones in a paper towel afterward to get them to sprout as well.
2. Plant Seeds
Now, you need to plant your germinated weed seeds. You will need to gather tweezers, growing medium, and a pencil. You should also have a small container or lightproof pot. Once you have everything you need, fill the container with soil or another type of growing medium.
The soil should reach just below the top of the container. Many growers fill it up to about 1 centimeter from the top. Then, you would make a small dimple in the dirt with a pencil. The hole should be a couple of centimeters deep.
Use the tweezers to pick up the seed and carefully place it in the dimple. When it is in the hole, you can cover it with a layer of soil. It is necessary to avoid pressing down firmly on the growing medium. The sprouting seedling could have a harder time emerging from the topsoil.
Spray some water to dampen the soil, but you should not add any nutrients at this time.
3. Switch Lights to 12-12
After a couple of weeks, you will see the seedling get bigger. You then can switch the lighting schedule to be 12-12 around the 3-week mark. The plant should start flowering as early as possible. Once it does, you can expect most strains to take roughly 12 weeks to be ready to harvest.
Many seedlings do not begin to flower immediately under a 12-12 light cycle. They usually do not start producing buds until they are 3-4 weeks old. It will not be long until you see some desirable results.
Tips for the Best Results on Growing 12-12 From Seed
Stay On Top of Your Plant’s Need
Even though the life cycle is shorter than usual, you should still pay attention to the plant’s needs. You have to monitor airflow, soil pH levels, and water quality like you would during regular marijuana growing.
Pests and mold can still be a problem. The plants can experience stress, which may mean stunted growth. Not to mention, the number of nutrients a plant receives can change as it gets bigger. You do not want the young seedling to suffer from any deficiencies or burns.
Some growers are concerned that growing 12-12 from seeds reduces yield sizes, but all these factors can ensure a maximized harvest.
Use the SoG Method
If you want to boost your yield size, you can use something called Sea of Green (SoG). The SoG method involves growing many small plants together instead of larger ones. You would place one or two plants down for every square foot.
The SoG setup does not require much effort, and you can grow various strains. However, you would need at least four plants for this method.
The technique works well with growing 12-12 from seed. You would change the light cycle around the third or fourth week, which increases how much you harvest in the end.
Do Not Use Autoflowers
Growing seeds under a 12-12 schedule would not be effective for autoflower plants. You would not be able to get the results you want. The reason is that autoflowers do not need a light cycle to transition to the flowering phase.
As a result, it would not matter if you use a 12-12 or 18-6 schedule. The autoflower plants have their own timeline, and you have less control of their flowering pace. A few autoflower strains might reach harvest sooner than other seeds.
You can buy one that reaches its harvest time quickly if you need to finish growing cannabis sooner.
Final Thoughts on Growing 12-12 From Seed
Many growers like to grow 12-12 from seed, and others do not. You can try it out to see if the method is something you will enjoy. A part of marijuana cultivation is figuring out what works best for you.
Before you get started, you should buy some suitable strains for growing 12-12 from seed. The ones that react the best have a fair share of Indica genetics. The light change is not as effective for Sativa-dominant seeds.
One strain you can try is the Big Bud. The plant naturally has the potential for a large harvest, so you could get more when growing 12-12 from seed. The strain also is great for SoG if you choose to apply the method.
Grape Ape seeds can grow under almost any condition. They can have significant yield sizes and have high THC content. Alternatively, Pinkman Goo is a mixture of other great strains. While sticky, you can get some tasty buds.
Is 12-12 From Seed Worth It?
Will the “12/12 from seed” cannabis growing technique give you huge yields? In a word, no… but there are benefits to initiating the flowering stage as soon as possible. Giving a 12/12 light schedule from seed germination is a great way to create tiny “bud stick” cannabis plants, which may be perfect for a small stealthy marijuana garden. When modified slightly, the same basic technique can create bigger plants and bigger yields while adding little to no extra time before harvest. And then there is the matter of genetics. Certain strains give better results than others.
The “12 /12 from seed” technique aims to initiate the flowering stage immediately after germination. Learn about cannabis light schedules.
This creates small “bud stick” plants that are typically ready to harvest in 3-4 months. Check out this beautiful example of “12/12 from seed” by Fuel.
If you haven’t heard this term before, “12/12 from seed” means giving your cannabis seedling 12 hours of light and 12 hours of dark each day from the moment of germination. Providing a 12/12 light schedule initiates the flowering stage and causes cannabis plants to start making buds. The idea of this technique is to get seedlings to start flowering as quickly as possible to reduce the time to harvest. Once a plant has started flowering, most strains are ready to harvest within 12 weeks. The sooner you get a plant to start flowering, the sooner you get to harvest.
There’s just one major problem… 12/12 from seed often causes stunted growth and small yields. This results in yields that are often less than 1 ounce per plant, even under strong grow lights.
This seedling took nearly 4 months from seed to harvest under about 150W of fluorescent lights and yielded only 1/2 of an ounce.
I think it looks kind of cool, but 1/2 ounces is not a great harvest after waiting so long. I’ve found you can tweak the light schedule to double or triple your total yield per plant without necessarily increasing time-to-harvest or plant height. More on that below!
12/12 from Seed – What You Need to Know
Something that’s a bit confusing about 12/12 from seed is it seems like seedlings should start flowering immediately. They don’t. I’ve found that photoperiod seedlings won’t start flowering until they’re 3-4 weeks old no matter the light schedule. That means your harvest won’t come any sooner if you initiate 12/12 before seedlings are 3 weeks old. When you give the plant 3-4 weeks of 18+ hours a day, THEN switch to 12/12, you often get better results because plants are quite bigger when buds start forming, without adding much (if any) time to harvest.
Most seedlings won’t make buds until they’re at least 3 weeks old from germination. There’s nothing you could do to get this little seedling to start flowering.
You often get better yields by giving plants 18+ hours of light a day for the first 3-4 weeks. These plants got 18/6 until they reached this size.
I started the 12/12 light schedule right after the above picture. They ended up yielding a lot more than my plants that were given 12/12 from seed in the same setup. Yet they didn’t get much taller or take longer to harvest.
Here are those same plants a month later after they started making buds (plants double or triple in height after the switch to 12/12, especially young plants)
A few weeks of extra light, in the beginning, seems to achieve plants with longer and fatter buds (why was this plant defoliated?)
Plants reward you for giving them a little more time to grow. For example, a solid 4 weeks of 18/6 before 12/12 creates plants that are ready to harvest around the same time as a plant given 12/12 from seed (3-4 months, depending on the strain), but significantly bigger yields.
If you’re worried about plants getting too big, you can gain complete control of plant shape by topping and bending plants to stay flat when they’re young. This increases the amount of bud produced without raising the overall height.
Many people who give 12/12 from seed have chosen this technique to ensure plants stay as small as possible. That’s why it’s common to see these plants in very small pots (like solo cups). Just like with bonsai trees, restricting root space is an effective way to reduce overall plant size. Plants kept in solo cups rarely get bigger than one long bud stick, especially when given 12/12 from seed.
Restricting root size reduces plant size dramatically, especially when combined with 12/12 from seed. Look how big this plant is in relation to the lighter!
12/12 From Clone – When You Want TINY Plants
If you want to grow the absolute smallest plant possible, “12/12 from clone” may be a better choice than 12/12 from seed. A clone is a piece of a bigger plant that was removed and forced to grow roots. Since a clone is technically the same “age” as its mother plant, it’s pretty much a mini mature plant as opposed to a seedling. Because they’re already mature, clones start flowering almost immediately after getting 12/12. That can result in some REALLY small plants at harvest.
Unlike seedlings, clones will start flowering almost immediately after getting 12/12. If you start with small clones in miniature pots, you end up with short buds on sticks at harvest.
These “12/12 from clone” plants are cute and fun! Though not necessarily the most productive when it comes to actual yields.
Auto-Flowering Strains – When Time is of the Essence
Some growers want to use 12/12 from seed to get to harvest as soon as possible, but it’s not actually the best option for a quick harvest. If you’d like to be able to harvest plants even sooner than 3 months, consider giving autoflowering plants a try. Most autoflowering strains are ready to harvest just 2-3 months from germination. That’s less time than almost any photoperiod plant will take, no matter what light schedule you provide. Even better, autoflowering plants on average yield 1-2 ounces each (more if you care for them well), which is better yields than most “12/12 from seed” plants.
The “modern” version of 12/12 from seed is simply using an autoflowering strain. They don’t need special light schedules and are ready to harvest in just 2-3 months from germination.
Autoflowering plants are typically given 18-24 hours of light a day their whole life, which allows them to get bigger in less time than plants under a 12/12 schedule.
Auto-flowering strains are ready in 2-3 months from seed, and yield an average of 1-2 ounces/plant. You can yield even more with low stress training (LST) and great care.
Use “Sea of Green” (SoG) to Maximize Photoperiod Yields
If you want to grow photoperiod strains (or can’t get your hands on autoflowering seeds) but still want to produce big yields as fast as possible, the “Sea of Green” grow style may be a good option. Sea of Green is simply the idea of growing many small plants instead of just a few bigger plants. It works great for photoperiod strains to produce a quick harvest and great yields. It’s kind of halfway between “12/12 from seed” and a typical grow.
For this grow style, growers usually switch to 12/12 when plants are 4-6 weeks old. Since adding a little extra time to the vegetative stage often increases yields, you need to find a balance between getting to harvest as quickly as possible versus harvesting the biggest yields.
For SoG, wait to switch to 12/12 until plants are about this size or a little bigger (note: young plants like this can and will double or triple in height after the switch to 12/12)
SoG in Action – Make sure to fill the entire space under the grow light with plants and you will get a sea of buds!