12 12 from seed

The 12-12 from seed technique – is it a good idea?

Indoor cannabis growers are always looking for new, speedier ways to grow high-quality weed indoors, in spite of the obvious space limitations. Some cultivators use a particular method known as the ‘12-12 From Seed‘ technique, which skips the traditional vegetative phase altogether.

Let’s look at what this means:

What does 12-12 from seed mean?

Photoperiod cannabis strains which are grown with feminized marijuana seeds reach the flowering phase based on their light cycle. To reproduce these conditions, indoor growers use different light cycles to keep plants in their vegetative stages and then force them to flower.

Therefore, they usually use an 18-6 light cycle to keep their plants in a vegetative phase for around two to four weeks and then switch to a 12 -2 cycle for the flowering stage, so the plants receive equal amounts of light and darkness.

This has been a standard indoor growing method for hundreds of years, and there isn’t anything particularly innovative about that. However, some growers use a cultivation technique known as the “12-12 From Seed” method.

As the name suggests, this is about skipping the initial vegetative phase and immediately forcing the plants into flowering as soon as the germinated seeds begin to protrude from the ground.

Advantages of the 12-12 from seed method

The 12-12 system saves you about five weeks’ worth of time and power. This makes the system a lot better for the environment than a system where there is a lengthy vegetative phase. Moreover, because you grow in this way, the cannabis plants have fewer leaves and relatively more bud. This makes them easier to harvest, and they have a nicely styled appearance. The 12-12 system works best for indoor cultivation, but can also be used outdoors by darkening.

  • Each part of the plant is fully exposed to the light – right down to the ground;
  • Less problem pruning because there are far fewer resinous leaves to process;
  • Plants are easier to handle for maintenance;
  • Cultivation is possible in tiny spaces;
  • Avoids wear and tear due to the displacement of components;
  • You’ll save money on electricity due to the shorter time to harvest.


  • You will need to spend more money on seeds at the beginning.

That’s pretty much it in terms of the negative side of the 12-12 from seed method, although some growers feel that it has a slight impact on the quality of the bud. Just give it a chance and find out if it works for you. Even if you decide it’s not for you after trying, the experience will help you learn more as a grower.

Tips for growing 12-12

  • Watch out for the humidity of the earth as lamps will dry out the soil faster than if a canopy protected it;
  • Start from the very beginning with 12 hours of light and 12 hours of darkness;
  • Avoid stress and provide plenty of high-quality light;
  • Place all plants in one large container with soil (or rock wool, clay granules, etc.).

Useing Sativa dominant cannabis strains – some Sativas will stretch up to 1.2 metres with this method, so selecting the right species early on is critical. Indicas are an obvious choice for maximum space savings. They are generally smaller, and the 12-12 technique will make them very manageable. You will love these little pots filled with bud stems, like a miniature fragrant forest. Buds grown this way are indistinguishable from plants that have gone through a vegetative phase when it comes to flavour and high, and ultimately having buds in your jar faster and more often is a good thing.

Feminised cannabis seeds are ideal with the 12-12 system, but regular cannabis seeds may be a bit cheaper when you start working with the 12-12 system. In that case, sow more plants and keep a close eye on the plants. As soon as you recognise males (after a week or two, the first bloom starts), you should remove them. The results are best when you put the plants in one large container with this system. This will allow them to compete with each other for the light and quickly climb up and still reach a nice size. In this way, you can save a lot of costs on energy and thus relieve the environment while you can quickly harvest as much or even more weed.

The top 3 best strains for 12-12 from seed

Want to grow a strain 12-12 from seed? These species are suitable:

1. Jack Herer

Named after a renowned cannabis activist, Jack Herer has won nine elite awards and is recognised as a caviare of hybrid strains. It has also received one of the highest pinnacles of achievement – the license to be distributed under medical supervision in Dutch pharmacies, thanks to its recognised therapeutic qualities.

The “high” of the tropical Sativa and the colossal resin production of the Indica form a sublime alliance in Jack Herer. The fully mature buds are covered so densely with translucent hair that they resemble icing sugar or appear to sparkle with dewdrops.

Three of the four main Jack phenotypes have a marked Sativa tendency. In contrast, the fourth has an Indica-like growth pattern – fast flowering and relatively compact, dense structure, abundant and rounded “buds” suitable for commercial cultivation. These characteristics make Jack Herer the ideal choice for the 12-12 from seed method.

Jack’s Sativa phenotypes can also give a good yield per yard or per plant when cultivated with care. The trait that all Jack Herer phenotypes have in common is their dazzling double-acting potency – a stratospheric cerebral “high” reinforced by an impressive stone of seismic power. Smokers should be prepared to experience something like an earthquake – which can be a very enjoyable feeling when their head is firmly planted in the clouds.

2. Bruce Banner

Bruce Banner is one of the most iconic and one of the strongest cannabis strains of all time. Bruce Banner is a particularly flavourful cross of the famous Kush aroma and diesel undertones. With 50% Sativa and 50% Indica genetics, it achieves high THC percentages and is very mould resistant.

The Bruce Banner strain is an innovative phenotype bred by crossing a Strawberry Diesel and an OG Kush. Some phenotypes have even been measured with 27% + THC! In other words, if a friend offers you Bruce Banner, take it easy!

The high starts with an intense “punch in the face”, then quickly transitions to a happy, giggly euphoria. After a potential laugh kick, Bruce Banner lets you sink into the couch where you will experience a state of extreme relaxation.

Bruce Banner is undoubtedly a strain for the true cannabis connoisseur who wants to add unique high-grade cannabis to their stash.

Bruce Banner also behaves wonderfully in your grow tent not necessarily growing as a dominant Sativa or a dominant Indica. It does not stretch very hard in flowering so works well for the 12-12 from seed method.

Make sure you take the time to cure this strain properly! This is very important to maintain this excellent terpene profile.

More information | Bruce banner strain seeds

3. Northern Lights

Northern Lights is one of the last few pure Indicas. This makes her grow robust and compact, terms that also apply to her buds. During flowering, this plant gives off relatively little odour, making it very suitable for the discreet cannabis grower!

Forty years ago, Northern Lights set the standard that other Indicas are still judged by today. The Lady remains one of the most trusted names and most demanded varieties in cannabis culture today. She dominated the various harvest festivals for years, winning prize after prize. This led to multiple requests to withdraw her from competitions so that the competition would also have a chance to win a title.

Like most of its relatives, this strain is usually grown indoors under lights. She also does very well outdoors, due to her mainly Indica genetics.

Northern Lights carries on the traditions of her classic ancestors, producing fast, reliable yields with surprisingly little smell during the grow. Still, her buds have a sweet scent and are incredibly potent due to their thick coating of THC-rich trichomes!

What are the advantages of growing 12 – 12 from seed and how to apply this method? Check it out!

Is 12-12 From Seed Worth It?

Will 12/12 from seed 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 is a great way to create tiny “bud stick” plants, which may be perfect for a small stealthy 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!

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!