12-12 From Seed - Flowering Plants Early

by Nebula Haze

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).

Wait, why does a 12-12 lighting schedule force cannabis plants to start making 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...

Read one grower's tutorial on how to force marijuana to flower from seed with 12-12 lighting

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.

Jump to...

Auto-Flowering Strains - A better way to force plants to flower early

Plant Training Techniques - Make your plants grow how you want

Cannabis Nutrient Problems - Picture Guide

Learn About Grow Lights - Which is best for your setup?