Is 12-12 From Seed Worth It?

by Nebula Haze

Is 12/12 from seed worth it? Is it a good way to get big yields as quickly as possible? In a word, no… but there is truth to the idea behind initiating the flowering stage as soon as possible! When modified slightly, the same basic technique will give you much bigger yields while adding little to no extra time before harvest.

A “12 /12” light schedule means giving your plant 12 hours light & 12 hours darkness each day (this initiates the cannabis flowering stage)

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 is to get a new seedling to start flowering as quickly as possible, so it takes less time to harvest.

There’s just one major problem… 12/12 from seed 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 4 months from seed to harvest, and yielded only 1/2 of an ounce. I think it looks kind of cool, but 1/2 ounces is not a good harvest after waiting so long. You can double or triple your total yields per plant by tweaking the light schedule a little during the first few weeks

This cannabis plant was given a light schedule of 12/12 from seed - although it looked pretty cool, it didn't end up yielding very much

The problem is that seedlings can’t start flowering until they’re 3-4 weeks old no matter what light schedule you give them, so there’s no point in starting right at 12/12 when they’re under 3 weeks old. When you give the plant 3-4 weeks of 18/6, THEN switch to 12/12, you will get far better results because the plant will get more light in those crucial first few weeks and end up much bigger by the time it’s ready to make the switch.

These plants are 3-4 weeks old and have been under a 18/6 light schedule from seed

Sea of Green (SoG) setup

A 12/12 light schedule was initiated right after the above picture. Here are those same plants a little over a month later, after they’ve started making buds (plants will double or triple in height after the switch to 12/12, especially young plants). As you can see, they are already far bigger plants than the first example, and bigger plants can support bigger buds.

Sea of Green example in the flowering stage

This is how you achieve plants that look like the one below at harvest (why was this plant defoliated?). Because the plant was allowed to get bigger before it started flowering, it yielded 3-4 times as much as the plant given 12/12 from seed.

Cannabis plant growing with one main cola after being switched to 12/12 at around 3.5 weeks old from seed

By giving plants just a little more time to grow before initiating 12/12, you will be rewarded at harvest time. If you give your plant a solid 4 weeks of 18/6 first, your plant will be ready to harvest around the same time as a plant given 12/12 from seed (~3.5 months, maybe a few days later), but you will get far bigger yields.

What is “Sea of Green” (SoG)?

“Sea of green” is the idea of growing many small plants instead of just a few bigger plants. The advantage is that you are able to get to harvest more quickly because each plant doesn’t have to grow as big to support the same number of bud sites.

Read full tutorial on Sea of Green

For this grow style, growers usually switch to flowering when plants are around 4-6 weeks old; plants switched sooner than 4 weeks may not have enough time to really get the most out of a SoG setup. Adding an extra week or two of veg can make a pretty big difference on yields though, so it’s about finding that balance between getting to harvest as quickly as possible versus harvesting a lot of bud.

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)

Switch to 12/12 when plants are around this side in order to start a SoG (sea of green) style cannabis grow

SoG in Action

Amazing example of well-trained cannabis plants - training your plants this way can increase your yields by up to 40%

Auto-Flowering Strains – When Time is of the Essence!

Is time really of the essence for you? If so, one of the best ways to maximize yields in as little time as possible is to grow an auto-flowering strain. Autos get 18 hours of light a day their whole life, which allows them to get bigger in less time than plants under 12/12. Auto-flowering plants on average are ready to harvest in just 3 months from seed (which is less time than almost any photoperiod plant will be ready to harvest, no matter what light schedule you provide) and generally yield 1-2 ounces per plant.

Auto-flowering strains are ready as soon as 3 months from seed, and yield an average of 1-2 ounces/plant, and possibly even more if you do low stress training (LST).

This auto-flowering plant was 3 months old (from seed) and yielded about 2 ounces of bud



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