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).
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.
Auto-Flowering Strains – A better way to force plants to flower early
Plant Training Techniques – Make your plants grow how you want
Learn About Grow Lights – Which is best for your setup?
Learn what it means to give your plants "12-12 from seed" to force them to start making buds early.
How to Grow Small Cannabis Plants in Tiny Spaces
Do you want to grow tiny cannabis plants? Would you like to build a “microgrowery” for your marijuana garden? This tiny plant tutorial will teach you how to grow cannabis plants that stay small yet still produce an abundance of weed! I’ve grown a lot of cannabis plants of all sizes, and I’ll share the most helpful tips and tricks to make cannabis plants grow in the exact shape and size you want.
Small plants are easy to hide, yet can still produce a surprising amount of weed. Here are some short cannabis plants I’ve grown:
LEDs are probably your best choice in a small space. This tent is only 3 feet (90 cm) tall.
Here is that tent just before harvest. Notice the size of the slinky compared to the plants. This tutorial will show you how to create short plants with rows of buds in a small space like this.
This autoflowering plant grew into a tiny bud ball as a result of blue-spectrum LEDs and being topped after buds started forming (typically a no-no because it stunts autoflowering plants, but can be a good technique if you want to keep plants tiny)
I grew these plants in the same waist-high grow tent, but this time using a T5 fluorescent light. A T5 is another great choice for small spaces since they can be kept just inches away from plants. The downside is they produce more heat than LEDs. If you’re struggling with cold (for example growing a tiny garden in a garage or basement), fluorescent lights can help keep plants warm. If you want to minimize heat, LEDs are the way to go.
Then there’s the incredible world of solo cup plants. Restricted roots keep plants small. This autoflowering plant I’m growing now is just over a foot (30 cm) tall and buds are getting bigger every day.
Quick Summary (how to keep plants small without sacrificing yields)
Here’s a quick overview of the tutorial, then I’ll go into the detailed instructions below.
- Choose a strain that naturally stays small – Today you have access to almost any genetics, almost anywhere in the world. Quick-to-harvest autoflowering strains are often the best choice for producing small plants, though short stature photoperiod strains can work, too. This tutorial shares several strains that have performed great for me in short spaces, and then I’ll share instructions on how to grow your plants so they stay as small as possible.
Certain strains like this Black Jack Auto naturally stay small, while still producing great yields!
2.) Grow Setup
- Use the right grow light – Fluorescent lights (like CFLs or T5s) and certain LEDs are great choices for small grow spaces. I’ll break down the pros and cons of each and share the specific models that have kept plants short for me.
- Light spectrum – Grow lights with more blue in the spectrum tend to keep plants short, while grow lights with more red can encourage stretching.
- Restrict root space – Plants in big pots can become the size of trees! Keeping plants in smaller pots tends to keep them from getting as big (like a bonsai tree with restricted roots), but buds will still get fat as long as the plant is receiving plenty of light and nutrients.
- Pick a “short” grow style – Short plants are often created through one of these grow styles: “Sea of Green” (many small plants in small pots), “Screen of Green” (using a screen), Manifolding (massively manipulate plant shape at a very young age), or other types of plant training (more on that below).
Restricting root size also restricts overall plant size
3.) Growing Practices
- Keep grow lights as close as possible – Make sure your grow light is as close as possible without stressing plants. Strong light helps keep plants shorter.
- “Top” your plants – Cut off the top tip of the plant when it’s just a few weeks old. This technique is known as “topping” and causes plants to grow bushy and spread out as opposed to tall like a Christmas tree. As a bonus, you create extra bud sites for free.
- Plant training – Learn how to get any plant to stay the exact height and shape you want via “plant training” techniques. Even if your plants are already too big, this can help. Especially techniques such as LST (low stress training) and supercropping (extreme bending) can come in handy if you need to change your overall plant shape or reduce the height.
- Don’t wait too long to initiate flowering – This doesn’t apply to auto-flowering strains, but if you’re growing a photoperiod (regular) plant, initiate the flowering stage when the plant is half the final desired size. Plants typically double in size after receiving a 12/12 light schedule. Plant height can get out of control if you wait too long. I learned this one from experience!
Bending and tying down stems can be used to keep a cannabis plant almost totally flat
Choose a strain that naturally stays small
Some cannabis strains tend to grow really big and tall no matter what you do. If a strain is labeled as “XL”, stay away! However, some strains stay super small without you having to do much of anything.
Auto-flowering strains start making buds in about 3-4 weeks from germination and are typically ready to harvest in 2-3 months. Due to this quick life cycle, nearly all auto-flowering strains stay on the smaller size. However, look for autoflowering strains listed as being short if you want the smallest possible plants.
Recommended short auto-flowering strains
- Amnesia Auto by MSNL – I’ve harvested 3 of these plants and highly recommend the strain. They stayed small, grew sparkly buds with cerebral strong effects, and produced good-to-great yields
- Berry Auto by G13 Labs – Fruity strain that stays short, grows easily, and is ready to harvest quickly
- Black Jack Auto by Sweet Seeds – These plants naturally stay small while still producing great yields. If any branches get tall, they respond well to training. I really enjoyed the bud effects of this strain. They’re strong yet kind of unique. It reminds me of a sativa/haze with more of a body stone.
- Blue Critical Auto by Dinafem – The Blue Critical I grew stayed small, bushed out on its own, responded extremely well to training, and buds came out fat and super potent! A joy to grow.
- Cinderella Jack Auto by Dutch Passion – When I grew this strain, the plant stayed small and produced solid, dense buds. The buds ended up being popular because the effects were curiously strong and long-lasting.
- Cream Cookies Auto by FastBuds Seeds – The bud quality is out of this world. And look beautiful in pictures! Each plant stays short, is easy to grow, and yields well.
- Cream Mandarin Auto by Sweet Seeds – This strain tends to stay very small, sometimes almost runty. Although the citrus-smelling buds aren’t the biggest, they’re ready to harvest quickly and produce captivating effects.
- Pineapple Express Auto by G13 Labs – An extremely popular autoflowering strain; plants stay short, are quick-to-harvest even for an auto, and the sparkle-encrusted buds smell like heaven.
- Pink Kush CBD 30:1 by Seedsman – Medicinal strain with under 0.5% THC, beautiful buds, quick-to-harvest
- Red Poison Auto by Sweet Seeds – This breeder has created several epic autoflowering strains, but the Red Poison Auto may be my favorite. I love the crazy red/purple color (which shows up on most plants, especially if the plant gets cool nights close to harvest), good yields, and dreamy bud effects.
- Tangerine Dream Auto by Barney’s Farm – The intoxicating smell of citrus on a tiny, high yielding plant. What more could you want?
- THC Bomb Auto by Bomb Seeds – I’ve grown 5 different plants of this strain over multiple grows in different setups, and every one came out excellent. Easy to grow, great yields, beautiful sparkly buds, and potent. Highly recommended!
- Wedding Cheesecake Auto by FastBuds Seeds – Stays pretty small, quick to harvest, and buds produce powerful effects.
This Amnesia Auto by MSNL stayed small but produced a surprising amount of bud!
Decent sized buds for the compact size
THC Bomb Auto grows thick buds without needing a lot of height, and buds are POTENT
You can also choose photoperiod plants listed as “short” strains. Strains listed as “FAST” or “Express” may be candidates for a short grow space because they have a quick flowering period, but it’s good to read the description to learn more about what height to expect. Photoperiod plants typically get bigger than autoflowering plants, but they can be a great choice for a small space as long as you get a suitable strain and make sure to initiate the flowering stage when plants are 3-4 weeks old. Don’t let them get too big before you initiate 12/12 or they’ll overgrow your garden!
Recommended short photoperiod strains
- Aurora Indica by Nirvana – Plants are fast-growing with dense, potent buds, yet they stay short and are ready to harvest quickly.
- Candy Kush Express FAST by Royal Queen Seeds – Easy to grow and quick to harvest. Buds smell divine and effects are extremely relaxing.
- Cream Caramel FAST by Sweet Seeds – Great yields on such a fast-flowering plant, tantalizing bud smell, and lovely effects.
- Original Amnesia by Dinafem – This strain isn’t particularly quick to harvest but doesn’t get very tall. Plants respond positively to plant training including manifolding. Buds are big and beautiful, with effects that live up to the name “amnesia”
- Peyote Critical by Barney’s Farm – Trippy effects on this strain. Plants stay short with training. Try to initiate the flowering stage before 4 weeks from germination and it shouldn’t get too big.
- Romulan – This strain is extra popular where I live right now. Romulan plants stay short and buds are high in THC. Although it doesn’t have the best yields, the bud quality is worth it.
- Royal Cookies by Royal Queen Seeds – Created from the extremely popular Girl Scout Cookies Forum Cut, this strain delivers beautiful American genetics with a punch, and plants stay small enough for a stealthy garden.
- Speedy Chile FAST by Royal Queen Seeds – Grow ultra sparkly buds on a tiny plant. The effects are relaxing and may help with anxiety.
- Sweet Russian by Garden of Green – Nice looking buds, stays small, yields well, good effects.
- Sweet Tooth by Barney’s Farm – I’ve grown this strain a few times over the years, and it always stays short with good effects. However, BF seems to be improving and refining this classic strain for potency because when I grew this strain again last year, the buds felt more powerful than ever. Highly recommended!
- THC Bomb by Bomb Seeds – Stays small, yields big, with excellent potency and sparkly buds. Can’t go wrong with this one.
Aurora Indica stays short and produces tons of buds
Original Amnesia responds well to plant training such as being manifolded
2.) Grow Setup
Use the right grow light – CFLs, T5s, and certain LEDs are great choices for small grow spaces. I’ll break down the pros and cons of each and share the specific models that have kept plants short for me.
CFLs give a lot of flexibility in tiny spaces because they’re small and can be kept just inches from plants. How to grow with CFLs.
This is my very first short plant, grown under a few big CFLs.
The plant was less than 1′ tall at harvest yet produced 1.5 ounces of bud. CFLs can produce good yields with small plants, but CFL bulbs that are big (or a lot of small CFLs) get hot and expensive. If you have space, I recommend upgrading to more efficient grow lights than CFLs.
T5 fluorescent lights are low profile, can be kept close to plants, and produce surprisingly good yields if you train plants to grow wide and flat like the plants here. The downside is they get much hotter than LEDs for the same electricity, and the yields aren’t as good per watt. How to grow with a T5 grow light.
LEDs come in a variety of shapes and sizes, so they can fit almost any setup. LEDs tend to be low on heat and electricity usage, which makes them great for small stealthy gardens. LED yields are excellent, too. On average, LEDs produce about twice the amount of dried flower as fluorescent lights like CFLs and T5s for the same electricity. The newer models of LEDs can yield even more. How to grow with LEDs in a mini tent.
These plants were grown in a 2’x2’x3′ tent under a 100W Quantum Board LED like this MarsHydro TS 600 (which is “600W equivalent” but actually only uses 100W)
Here is an example of the buds produced! (This was Auto Amnesia by MSNL)
Light spectrum – Grow lights with more blue in the spectrum tend to keep plants short, while grow lights with more red can encourage stretching. LEDs or bulbs labeled with a spectrum of 4000k, 5000k, and 6500k are great choices with plenty of blue to keep plants short.
This graphic represents the colors in visible light. Blue light encourages plants to stay short and bushy. Red light tends to cause marijuana plants to stretch and grow tall.
Restrict root space – Plants in big pots can become the size of trees! Keeping plants in smaller pots tends to keep them from getting as big (like a bonsai tree with restricted roots), though buds will still get huge as long as the plant is receiving plenty of light and nutrients.
Keeping plants in a small container causes them to stay smaller on average by restricting root size. This autoflowering plant grown in a solo cup barely grew to a foot tall.
These autoflowering plants were all germinated at the same time and even share 4 of the same strains. The little tent had 1-gallon pots, while the bigger tent used 3-gallon pots. The smaller pot size is a big part of why the plants in the mini tent stayed so much shorter and smaller.
Here’s another example showing how pot size makes a difference to plant size. These plants were all germinated at the same time in Rapid Rooters. Right before this picture I planted some of the seedlings in 3-gallon pots, and the others in solo cups. They were all about the same size at this point.
Within a week, the plants in bigger pots overtook the plants in solo cups. Most actually had an extra set of leaves compared to their solo cup siblings. The size difference would only have kept getting more vast if these plants were allowed to continue growing together. Small pots make small plants! Here’s a timelapse of that week if you want to check it out.
Pick a “short” grow style – Short plants are often created through one of these grow styles…
- Sea of Green (SoG) keeps many small plants in small pots
- Screen of Green (ScrOG) trains plants to grow along a screen or net, which forces them to stay about the same height
- Manifolding is a process that massively manipulates plant shape at a very young age for a bushy, symmetrical plant
- Other types of plant training such as Low Stress Training (LST) and Supercropping (extreme bending) can also be helpful to keep plants short
Sea of Green (SoG) – Many small plants
Screen of Green (ScrOG) uses a screen or net
Here’s another example of a net being used to help keep plants short and flat
Manifolding creates a solid main trunk with several symmetrical branches. This allows you to achieve monstrous yields on a relatively small plant.
Other types of pruning and manipulation such as Low Stress Training (LST) and Supercropping (extreme bending) can be used to create almost any size or shape plant
3.) Growing Practices
Keep grow lights as close as possible – Make sure your grow light is as close as possible without stressing plants. Strong light helps keep plants shorter. How far should I keep my grow lights?
“Top” your plants – Cut off the top of the plant when it’s just a few weeks old. This technique is known as “topping” and causes plants to grow more spread out as opposed to tall. You want a short bush, not a tall Christmas tree. Learn all about topping.
“Top” your plants when they’re 3-4 weeks old
A good time to top a plant is when it has about 6 sets of leaves
To top a plant, you cut off the top by clipping through the main stem
Topping makes plants grow more wide and bushy instead of tall. As a bonus, it increases the total number of main bud sites and improves yields!
Autoflowering Tip: Top an autoflowering plant after it’s already started making buds to keep it shorter. Topping in the flowering stage is normally considered a bad idea because it stunts most autoflowering plants, but can be a good tactic if you want to stunt the plant on purpose.
Topping after buds had already started forming caused this plant to stay extra small.
Here’s another example of a plant that was topped after it had already started making buds
Plant training – “Plant training” techniques give you ultimate power to create plants of nearly any size or shape.
Training techniques such as LST (low stress training) and supercropping (extreme bending) are especially handy if you need to change your overall plant form or reduce the height.
The grower wants to keep plants as short as possible
As the plants grew, she regularly bent all the top branches over and tied them down
That’s how these tiny plants were made!
Use bending to reduce the height of tall branches. Don’t forget to tie the branches down or they’ll turn back up! (I like plant twist tie for hooking around stems)
The arrow points to the twist tie that was used to hold down the branches as this plant grew
Use supercropping to bend at right angles without breaking your stems. This can be especially helpful if you’re plants are already too tall for your space.
Some growers take plant training to extreme levels
Check out the “skeleton” of the above plant after harvest. The grower basically trained the main stem to grow in a flat spiral around the base. So much bud in such a small area!
You can produce impressive buds on a small plant with a powerful grow light and high-yielding genetics
It’s amazing what can be accomplished with a little bending and tying down as your plant grows!
Don’t wait too long to initiate flowering – This doesn’t apply to auto-flowering strains, but if you’re growing a photoperiod (regular) plant, initiate the flowering stage when the plant is half the final desired size. Plants typically double in size after receiving a 12/12 light schedule, so plant height can get out of control if you wait too long.
Initiate 12/12 when your plant is about half the final desired size
Plant about double in height before harvest, though some strains “stretch” more or less (notice how the back left plant from the above tent got taller than the rest). Genetics make a huge difference! Learn more about the flowering stretch.
You should now have a solid understanding of what it takes to grow marijuana plants in any size or shape you want!
How to Grow Small Cannabis Plants in Tiny Spaces Do you want to grow tiny cannabis plants? Would you like to build a “microgrowery” for your marijuana garden? This tiny plant tutorial will teach