Cannabis 12/12 From Seed

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We explore whether you can skip the 18/6 light cycle and immediately begin using the 12/12 light cycle after sprouting your marijuana seeds. Power Plant grow review, from seed to harvest under a 12/12 light system. Power Plant remains one of Dutch Passions most appreciated varieties. 12/12 from seed to harvest is an outdated method of growing weed, but not a bad cycle for bag seeds and perpetual harvest. Learn more!

Can you use the 12/12 Light Cycle immediately from Seed?

While continuing our exploration of cannabis light cycles, we now turn our attention to the concept of skipping the vegetative light cycle and going straight to the flowering light cycle.

Is it possible to begin the 12/12 light cycle immediately after sprouting a seed?

A question that comes up from time to time is whether it’s possible to skip the 18/6 vegetative light cycle and go straight to the 12/12 light cycle after sprouting a seed. In theory, the answer should be “yes.” Theoretically speaking, a marijuana plant will still produce buds if subjected to 12 hours of light and 12 hours of darkness.

But theory and real life practice don’t always match up. The only way to truly know is to test the theory with an experiment.

So we have to decided to test this theory by launching a series on flowering cannabis straight from seed. We have never done this before, so we are excited to see what happens!

How to Grow Marijuana Indoors: The Two Light Cycles You Must Use

As we have explained before, Cannabis is a photoperiod plant, with two distinct photoperiods: the vegetative period and the flowering or bloom period.

The 18/6 Vegetative Light Cycle

The vegetative period is the first of the two stages of the cannabis life cycle. During the vegetative stage, the plants grow taller and bigger, but never bloom. Because they never bloom, they remain immature and capable of being cloned. They can also be trained, by being bent, pruned, topped, and even twisted. In this immature state, they remain pliable and flexible.

The purpose of the vegetative period is to allow the plant to grow, and to train the plant before it begins blooming.

The ideal light cycle for the vegetative period is 18 hours of light, six hours of darkness. However, many other light cycles that can be used, such as 20/4 or simply keeping the lights on 24 hours a day, with no darkness.

The 12/12 Bloom Light Cycle

In order to make the plants bloom, they must receive much less light than during the vegetative phase. In fact, cannabis plants must receive at least the same amount of darkness as light in order to produce bud. And if they receive more darkness than light, that is fine too.

Why Skip the vegetative stage?

Why would you want to skip the vegetative stage and immediately begin flowering your seedling? This is a question worth asking.

Without having conducted this experiment, we can hypothesize the advantages and disadvantages of skipping the 18/6 light cycle.

Advantages of skipping or shortening the Vegetative Light Cycle

The perceived advantage would be shorter wait time to harvesting flower. If you take a seedling and put it under a 12/12 light cycle, you are only 60 days away from harvesting actual bud. This is a shorter time period than you would get using autoflowers – strains that are specifically bred to flower without having to even change the light cycle.

There are other perceived advantages, such as more harvests per year.

If you are using the same space for veg and flower, then you will also be able to pull down more harvests per year. A lot more.

Disadvantages to skipping the Vegetative Light Cycle

The main disadvantage will be your yield per plant. A 10-day old seedling is not very big, and even if it triples in size during the 12/12 light cycle, it will still not be that big after 60 days. A smaller plant will always yield less bud than a bigger plant of the same pheno.

The other perceived advantage – more harvests per year – only applies if you are growing in a single room for both vegetative and flowering stages. By simply having more grow spaces — whether rooms or tents – you can get the same number of harvests per year. So this advantage goes away simply by expanding your grow spaces.

There is also the question of whether the quality of bud will be the same without the additional growth that occurs during the vegetative period.

There is only one way to find out.

A video series on using the 12/12 light cycle from seed

We chose to conduct an experiment on this topic. And we documented the entire process. You can read and watch it here:

Power Plant Grow Review. Grown from seed to harvest under 12/12 light

Power Plant remains one of Dutch Passions most appreciated genetic contributions in recent decades. This weeks blog is about a Power Plant grow review. A customer grew his Power Plants from seed to harvest under a 12/12 light system in 3.5 litre pots in just 85 days averaging around 50g harvest per plant.

Dutch Passion Power Plant has been a best-seller since the 1990’s, she’s a South African sativa with heavy yields and fast growth, but she is probably most appreciated for the hard-hitting knockout smoke. As one of our original legendary varieties we offer this variety in both regular and feminized seeds. The following comments and pictures in the grow diary come from Automaster, his original diary is here.

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Above and below. Power Plant grown under a 12/12 light cycle, a fast way to grow.

Growing method

“My Regular Power Plant seeds were put into flower (12 hours light/12 hours darkness). They were germinated in their final 3.5litre containers of organic soil. This means that 4 Power Plants can go into a 15 litre pot footprint, a very efficient use of soil.”

“This growing method (grown from start to finish under 12/12 lighting) delivers superb efficiency saving 21 days of vegetive growth under 18/6 veg light and reducing water loss through evaporation. I used half the usual water with this method, and therefore less nutrient. The 3.5 litre pots are much easier to rotate 180 degree’s daily and move around than larger containers. Due to the 3.5 litre container size I flushed the plants for 2 days with pure water every 10 days. This helped to keep any un-used salts/minerals down to a minimum. ”

“I grew from regular seed and got 54% male plants. The EC (electrical conductivity) of feed was kept low since pure sativas are generally light feeders. Starting EC was 0.2, and final EC was 0.6, pK 13/14 was substituted for nutrients for the last 4wks of flower. Canna flower boost was also used @1ml/ltr to facilitate pK uptake into the flowers. Rootball temperature had a minimum 21ºC and a maximum of 28ºC. I find that sativa dominant varieties are not troubled by higher temperatures. ”

70 days after germination

“70 days after germination around 80% of trichomes where very milky. So i could have harvested them at that point. However I gave them 85 days until the trichomes were 30% amber. Starting the grow under 12/12 allows you to start your next crop of seedlings in the same tent as the maturing plants. It saves time and electricity. This fast grow system allows you to harvest 4-5 times in 365 days using a 12/12 regime.”

“Sativa dominant varieties seem to like this grow method, I had 4 plants which reached 1.2m tall but most were 80-90cm. The trim waste all went into one bag ! Its a very low waste growing method since there isn’t a lot left over ! 12/12 from seed is a great way of controlling the ‘sativa stretch’ height issues. This stretch can be 2metres+ in 15 litre containers in normal grow situations.”

“The smoke is legendary, and I now see why. It’s very smooth with THC power above 15%. Roses and old school flavors abound. It’s a very pleasant taste, and vape/combustion aroma from the reg Power Plant is superb on the nose. Very, very crispy dried flowers (RH62%) with trichome load delivered by Power Plant. A super sativa qualifier and no doubt.”

Congratulations to AutoMaster for showing us the unusual method of growing under 12/12 light conditions from start to end. Its a fast way to grow that can allow growers to achieve more grow cycles without compromising quality.

P.s. find lots more about Dutch Passion and our varieties on Facebook.

12/12 From Seed to Harvest: When to Choose This Method

Doing 12/12 from seed is mostly a relic of a bygone era, but it’s not a bad way of growing weed and can even offer optimal results in some situations.

The 12/12 from seed to harvest method is a bit outdated, but still has its uses. In this article you can learn everything about yields, pot size and plant size, flowering time — in short, all that you can expect when running 12/12 from seed in your grow.

If you have grown weed before, you probably understand what ‘12/12 cycle from seed’ means. And for the novice growers, the following short paragraph explains all the science.

Cannabis is a short-day plant, meaning that it only starts to flower when days become short enough at the end of summer or the beginning of fall. Indoors, we mimic this by shortening the lighting cycle to 12 hours of light and 12 hours of darkness (12/12) and thus inducing the flowering. Usually, we do this after several weeks of the vegetative growth under 18/6, but sometimes you can reprogram your timer to 12-12 from the day your sprouts emerge. And this is exactly what we mean by 12/12 flowering from seed.

These Black Widows clones were put under 12 and 12 as soon as they rooted. Not exactly a 12-12 from seed scenario, but the idea is the same. Wonderful results btw.

Table of Contents

Growing Weed on 12/12 From Seed: Right Reasons and Wrong Ones

Frankly, this is a notoriously low-yielding method, so there must be other reasons to still choose it, right? Of course, there are.

1. Bagseed Growing

Okay, you’ve bought some buds with seeds in them, liked the smoke, and decided to give those bag seeds a try. Not the most brilliant idea ever, but okay. You don’t know how these seeds will turn out until they’re well into flowering, and this can be in like 1.5-2 months from sprouts (if grown in a regular way). Probably, too much time to spend on a dark horse, right? And here the 12/12-from-seed-no-veg method can easily save you 2-4 weeks or more.

2. Using Regular Seeds

It’s the same as with bagseeds. A certain percentage of regular seeds (probably around 50%) will grow into males, and you want to spot them and discard them as soon as possible. Again, 12/12 lighting from seed saves you several weeks of precious time.

3. Perpetual Harvest with no Extra Veg Room

Some people have just one grow space, but prefer to run a perpetual harvest operation. Obviously, your only grow room will be the flowering room, with lights running at 12/12 continuously. So the only way to add new plants after you’ve harvested some of their predecessors is to give the newcomers 12/12 from seed to harvest.

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4. You Don’t Care About Yield, But Value Variety

At one time, I was crazy about mix packs that some breeders sell because they gave me the opportunity to grow (and later enjoy) several different genetics in one go. So I used to put 9 different strains in my 2’x2’ grow tent and run them in a 12/12 cycle from seed. The yield per plant was underwhelming, but more than enough for me. The main thing was that every smoke came out different in terms of effect and flavor.

So, these were the good reasons to choose the 12/12 from seed to harvest method, and here are the bad ones:

  • Microgrow/Limited Height. In small grow spaces with a short distance to lights, you’ll probably be better off raising autoflowers in small containers. The alternative is having fewer plants, but training them in veg (topping, LST, ScrOG) to have a flat canopy. Both of these options will guarantee you better yields.
  • Weak lights. Some people who use tubular fluorescent lamps (like T5) or something similar (CFLs, LED bulbs) think that lighting systems of this kind call for a SOG grow with many budstick plants in solo cups. It’s probably true, but again autoflowering seeds will give you better results than photoperiod strains grown on 12/12 from seed to harvest. And yet again, simply training those during normal veg would be more effective, too.
  • Expectation of a faster turnover. Questions like “How long does 12/12 from seed take?” (which people ask all the time) prove that many of them regard this method as the fastest way to harvest. In fact, it doesn’t really make your plants finish much faster, if at all. More of it below.

Cloning/Reveg

There is one more aspect of growing weed 12 12 from seed that we have briefly touched upon when talking about bag seeds and regular seeds. Here it goes.

Some growers try out every bean they lay their hands on in search for a hidden gem. Well, it’s a noble quest, and the 12/12 from seed method allows you to quickly assess the genetics. But suppose you’ve found a phenotype you like. Now what?

You have two options: one is cloning a plant that is already flowering, the other is reverting it back to veg (a procedure known as ‘reveg’).

Taking a cutting from a flowering plant and then rooting it is a fairly difficult procedure compared to cloning in a regular way (when the plant is still in veg). It takes longer and the success rate is lower. (There is an upside, though: the resulting clone turns out into an insanely branchy little monster; hence the name of this procedure – monster cropping.) Another difficulty is that plants grown 12/12-style are basically a ‘bud on a stick’ and often have no side branches to use as cuttings.

What’s the Alternative to Reveg Then?

If you’re searching for a keeper, try vegging every plant for a few weeks, then take a back-up clone from each, and then flower all donor plants to see if there’s a champion among them. It’s easier this way.

The same goes for reveg. Reverting flowering plants back to veg is hardly a beginner-friendly procedure, and can take months (with no guarantee of success). Do you know that some growers in colder climates use this feature to have the harvest in the middle of summer? They make their plants flower indoors for 4 weeks, and then put them outside. And no reveg happens, even though summer days are much longer than nights. Why? Because reveg is a difficult process and requires so much more than simply reverting to 18/6 or even 24/0.

Revegging a plant after harvest is a painfully slow procedure with uncertain prospects.

12/12 From Seed vs Autoflower Growing

In many ways, the 12/12 from seed method is similar to the cultivation of autos, but autos have a much better potential because they can flower on 18, 20 or even 24 hours of light a day. All this extra energy will be transformed into extra bud weight and raised amounts of THC and terpenes. There was a time when autoflowers weren’t high-yielding or potent enough to compete with their photoperiod counterparts, but it’s long gone now. Today, the 12/12 from seed vs auto choice is a no brainer.

And by the same logic, the worst thing you can do is to grow an autoflower on 12/12 from seed. Sometimes people are forced to do this: for example, when there is some free space in the flowering room, but no extra seeds, except autoflowering ones, to fill it. But autos raised in this manner usually stay small and yield little.

12/12 From Seed Instructions and Tips

So, you have a grow room dedicated to the 12/12 from seed to harvest grow. Start by programming your timer so that the lights turn on for 12 hours of light every 24 hours, and then germinate some seeds using your favourite germination method.

This is what you may expect when growing weed in a 12/12 cycle from seed.

What Size Pot for 12/12 from Seed Works Best?

You don’t need a lot of space for your plants’ roots because the vegetative stage will be very short and then the root system basically stops growing. So use solo cups (party cups) or small plastic containers. The pot size can be anywhere from 16 oz (0.5 L) to a gallon (3.78 L). Keep in mind that the smaller the containers, the more frequently you’ll have to water them. More medium also means better buffering for nutrients and less risk of a nutrient burn.

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Also different strains react differently to 12 and 12 from seed. Some will take many weeks before they even start flowering, and they will require bigger containers. Growing in 1 litre pots will do fine for most varieties that are worth growing this way.

When Does Flowering Start?

Even on 12/12 from day one, weed plants don’t start flowering right away. Vegetative growth is an important process and will run its natural course. Expect at least 3-4 weeks before the plants are mature enough to show their sex. Of course, when it happens, they will start to flower immediately. As you can see, this is basically the same timeline as for autoflowers.

How Long till Harvest?

Most 12/12 enthusiasts report that their plants finish in 70+ days from sprouts, although some phenos can take up to 3-4 months. Again, autos can do much better than that, and they’ll yield more, too. The reason is that the yields are proportionate to the hours of light a plant receives, and you can give autos from 18 to 24 hours a day.

The Final Size and Yield

It all depends on a lot of factors — strain, pot size, lights etc. It can be as little as an eighth (3.5g) or less from a sickly runt in a solo cup, or up to a half ounce (14g) in a 16oz (0.5L) cup. In the latter case, the skinny one-cola plants will be upwards of 2 feet (60+cm).

This is how a harvested plant can look like if grown 12/12 from seed. Hardly inspiring. I’d even say vaguely humiliating.

Some 12/12 growers prefer even bigger plants in containers of up to a gallon (3.78L): their height can be 3-4 feet (90-120cm) and more, and the yield per plant of 0.5-1oz (14-28g) is considered very good. And it really is, if you grow many such plants SOG-style. There are even reports of plants yielding as much as 3 ounces (85g) each.

SOG (Sea of Green) is the Only Viable Option

Given that the size of the containers is quite small and the plants are lanky, with almost no side branches, we recommend cramming as many of them as possible into your grow space. This way your yield per square meter can prove to be not so bad after all: let’s say 30 half-ounce plants under a 1000W HPS. Hardly record-breaking for a SOG grow, but still.

Topping/Pinching

Would-be 12/12 growers often wonder whether they can train their plants or not. I think the logic here is the same as with autos: any HST technique, like topping, would just lower the yields and (possibly) delay the harvest time. Besides, any training method, including LST, raises the question of spacing: if the plants stand next to each other in tight rows, you shouldn’t try to make them wider and bushier. The single-cola pattern is probably the best.

The Best Strains For 12/12 From Seed To Harvest… and the Worst

As we have said earlier, this method is best reserved for seeds of unknown origin and potential. But if you insist on growing store-bought seeds this way, choose an indica. Indica strains tend to react quite early to the change in light cycle, and if you give them 12/12 from sprouts, the veg will be very short and the plants will remain nice and compact.

As for sativas (like Haze) and sativa-dominant genetics, they have evolved in regions near the equator where days and nights are close to an equal length the whole year. So, they can remain in veg for many weeks and even months before they even show their sex. It kind of defeats the purpose of 12/12. The plants will be neither fast, nor small, and the yields will be disappointing because of too little light hours received in veg.

12/12 From Seed Feeding Schedule

The first thing you should take care of is the development of roots. We recommend using some rooting stimulator when watering your plants in the first two weeks or so.

As for nitrogen-rich fertilizers, it all depends on the pot size. In bigger containers, the soil will probably have enough nutrients to last for the whole of veg. In smaller pots or cups, the plants will need a nitro boost early on. Continue to feed them with veg nutrients till they reach the final height and stop stretching further. This usually means a couple of weeks into flowering.

Starting in the third week from seeds, introduce the bloom fertilizers (with raised P-K levels). First use them along the veg ferts and then without them. 2 weeks before the harvest is time to start the final flush.

The Bottom Line

There are a few special situations where the 12/12 from seed to harvest method can lead to results that are by no means spectacular, but optimal under given conditions. In most other cases, using it would be a mistake. Always check whether you can achieve the same goal with autoflowers, or other growing methods. And if you don’t agree, please share your opinions in the comments.

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