Is 12-12 From Seed Worth It?
Will the “12/12 from seed” cannabis growing technique 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 germination is a great way to create tiny “bud stick” cannabis plants, which may be perfect for a small stealthy marijuana 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!
4 stages of marijuana plant growth
Cannabis plants go through a series of stages as they grow and mature, and those different growth stages call for different amounts of light, nutrients, and water.
It’s important to know these stages and how long each lasts to know what the plant needs and when. Knowing where your cannabis plants are in their life cycles will dictate when to prune, train, and trellis your plants, and when to harvest.
How long does it take to grow a marijuana plant?
Generally speaking, it takes anywhere from 10-32 weeks, or about 3-8 months, to grow a weed plant from seed to harvest. It’ll be quicker if you start with a clone or an autoflower seed.
The biggest variability in how long a marijuana plant takes to grow will happen in the vegetative stage—after the seedling phase and before flowering.
If you’re growing indoors, you can force a weed plant to flower after only a few weeks when it’s small or after several weeks when it’s big.
When growing outdoors, you’re at the whim of the seasons and will have to wait until the sun starts to go down in the fall for plants to flower, and then to harvest.
However, one way outdoor growers can control the flowering cycle is by using light deprivation techniques.
How long can a marijuana plant live?
Weed plants are annuals, meaning they grow and live for one season and then die. Wild cannabis plants grow seeds and drop them when they die, which will grow into new plants the following year.
When harvesting, plants are cut down and die in order to get their buds. New seeds need to be planted in order to grow more plants.
If left unharvested, weed plants will eventually wither and rot within a few months after the peak flowering phase.
When should you grow marijuana?
If you’re growing outdoors in the Northern Hemisphere, growers usually get their seeds between February and April and start germinating seeds by the end of April.
Many start growing seedlings inside in a more controlled environment because seedlings are more delicate, and then put the seedlings in the ground outside once they’re a little bigger and the weather is warmer.
If you’re growing clones or autoflowers, you have a grace period of another month or so. Plants usually need to be outside, in the ground, by the end of June.
Harvesting happens sometime between September and November. This depends on your local climate, as well as the weather that particular year—one year it could be the end of September, the next, end of October; growers in the Pacific Northwest will have to pull down their crops earlier than those in Northern California because of cold weather.
If you’re growing weed indoors, you can grow whenever you like. Keep in mind that the outside environment will affect your grow space—you may need to add heaters in the winter or fans and ACs in the summer.
Other than that, you can start seeds whenever you like and flip them into flower whenever you like, depending on how big you want the plants.
Important dates for growing marijuana outdoors
Many growers begin germinating seeds as early as February and March in order to have big plants come harvest time, but the Spring Equinox is a good reminder that it’s time to kick off the outdoor growing process and start germinating your seeds if you haven’t already.
Many farmers wait until after Mother’s Day in May to put their plants outside. Just make sure all of your plants are outside by the Summer Solstice at the latest.
The weather will start to turn and the sun will begin descending in the sky as your plants fatten up with sweet, sticky buds. It might be tempting, but the Fall Equinox is about when to start harvesting. It’ll depends on your climate and the year—it could happen a little before or after.
Everything should be cleaned up, dried, and curing by Thanksgiving, and in some places, even by Halloween.
As winter approaches, it’s prime time to make your own cannabutter, topicals, or tinctures with all that trim from the harvest. Kick your feet up, relax, and hunker down for the cold, it’s been a long growing season!
Notes on marijuana growth phases
We can’t stress enough that the timeframes in the above graphic are ranges of time for the Northern Hemisphere. You’ll need to adjust them based on your specific region and local weather and climate.
Be sure to keep a grow journal to track the progress of your plants. Looking back on your notes will help you learn from mistakes and maximize the quality and quantity of your buds next year.
Take meticulous notes on when and how you perform each step, noting:
- How much water you give plants, and at what intervals
- Nutrient amounts
- When you top and prune
Pictures will also give you a better sense of how your plants look along the way.
What are a weed plant’s growth stages?
The growth stages of marijuana can be broken down into four primary stages from seed to harvest:
- Germination (3-10 days)
- Seedling (2-3 weeks)
- Vegetative (3-16 weeks)
- Flowering (8-11 weeks)
Cannabis seed germination
Seed germination length: 3-10 days
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
The first marijuana plant stage begins with the seed. A cannabis seed should feel hard and dry, and be light- to dark-brown in color. An undeveloped seed is generally squishy and green or white in color and likely won’t germinate.
Once your seed has germinated, or sprouted, it’s ready to be placed in a growing medium, like soil. The tap root will drive down while the stem of the seedling will grow upward.
Two rounded cotyledon leaves will grow out from the stem as the plant unfolds from the protective casing of the seed. These initial leaves are responsible for taking in sunlight so the plant can grow healthy and stable.
As roots develop, the stalk will rise and you’ll begin to see the first iconic fan leaves grow, at which point your cannabis plant can be considered a seedling.
Seedling stage in cannabis plants
Seedling stage length: 2-3 weeks
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
When your marijuana plant becomes a seedling, you’ll notice it developing the traditional cannabis fan leaves. As a sprout, the seed will initially produce leaves with only one ridged blade.
Once new growth develops, the leaves will develop more blades, or “fingers” (3, 5, 7, etc.). A mature cannabis plant will have between 5 or 7 blades per leaf, but some plants may have more.
Cannabis plants are considered seedlings until they begin to develop leaves with the full number of blades on new fan leaves. A healthy seedling should be a vibrant green color.
Be careful to not overwater the plant in its seedling stage—its roots are so small, it doesn’t need much water to thrive.
At this stage, the plant is vulnerable to disease and mold. Keep its environment clean and monitor excess moisture. Be sure to give it plenty of light.
Even if growing outdoors, a lot of growers will start their seeds inside under an artificial light to help them through this delicate stage of marijuana growth.
If you buy a clone from a grower or breeder it will be a seedling, so you can skip the seed germination phase.
Vegetative stage in cannabis plants
Vegetative stage length: 3-16 weeks
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
The vegetative stage of cannabis is where the plant’s growth truly takes off, and it typically lasts 3-16 weeks. At this point, you’ve transplanted your plant into a larger pot and the roots and foliage are developing rapidly. This is also the time to begin topping or training your plants.
Be mindful to increase your watering as the plant develops. When it’s young, your plant will need water close to the stalk, but as it grows the roots will also grow outward, so start watering further away from the stalk in the soil so roots can stretch out and absorb water more efficiently.
Vegetative plants appreciate healthy soil with nutrients. Feed them with a high level of nitrogen at this stage.
If you need to determine the sex of your plants (to discard the males), they will start showing sex organs a few weeks into the veg stage. It’s imperative to separate males so they don’t pollinate the females.
Cannabis plant flowering stage
Flowering stage length: 8-11 weeks
Marijuana light cycle: 12 hours a day indoors; full, direct sun 6 hours a day outdoors
The flowering stage is the final stage of growth for a cannabis plant. This is when plants start to develop resinous buds and your hard work will be realized. Most strains flower in 8-9 weeks, but some can take even longer, especially some sativas.
Outdoors, flowering occurs naturally when the plant receives less light each day as summer turns into fall.
Indoor growers can trigger the flowering cycle by reducing the amount of light marijuana plants receive from 18 to 12 hours a day.
There are three subphases of the flowering stage:
- Flower initiation (week 1-3): The plant will continue to grow and females will develop pre-flowers—pistils, or white hairs, will grow out, which are the beginnings of buds.
- Mid-flowering (week 4-5): The plant itself will stop growing and buds will start fattening up.
- Late flowering/ripening (week 6 and on): Trichome density will increase and plants will get very sticky; keep an eye on the color of the pistils to tell when to harvest.
There are a number of changes to consider once plants go from the vegetative stage to the flowering stage:
- Don’t prune when plants are flowering, as it can upset their hormones
- Plants should be trellised or scrogged so buds will be supported as they develop and air can flow through plants
- Consider giving plants bloom or phosphorus nutrients
When do buds grow the most?
Buds typically grow the most toward the end of the flowering life cycle. You probably won’t notice much budding out at the beginning of the flowering stage, and it will slow down toward the end of the cycle, when buds become fully formed.
Once buds have reached full maturation, it’s time to harvest your marijuana. How long it takes to harvest buds depends on many factors, including harvesting methods and how many plants you harvest.
How to Grow Marijuana from Seed
If you’re in a location where cannabis (another term for marijuana; short for the plant cannabis sativa) is illegal, growing it is probably illegal too. Bringing in seeds or cuttings to your location can very well be a felony, and reputable sellers won’t ship to you.
You can probably purchase and grow hemp seeds and plants, which have a negligible amount of THC, but these plants won’t produce the psychoactive effects of plants that contain higher levels of THC. Check with your seller to be certain you’re getting what you think you’re purchasing. If you buy seeds for CBD-only hemp plants by mistake, you can end up being very disappointed post-harvest.
How to acquire seeds or cuttings
You can usually find cannabis seeds for sale at most dispensaries in areas where growing cannabis for personal use is legal. You may also find growers who sell cuttings/clones. You can expect to pay $50 to $100 for a pack of ten seeds. When shopping for seeds or cuttings, read the labels and any other information the manufacturer provides on its website or in its catalog to make sure you’re getting the right seeds or cuttings (the strain) for the plants you want to grow.
One way to get your mitts on some seeds is to collect seeds when you find them in flowers you purchased, or get some from friends if they’re collecting.
- Feminized seeds: Nearly all seeds sold by reputable companies are feminized, but make sure they are. These seeds are specially treated to grow into female plants.
- Auto-flowering or photoperiod: Auto-flowering plants are easier, because they enter the flower stage after a certain number of weeks regardless of the light/dark cycle. If you’re a beginner, seriously consider going with auto-flowering plants.
- Genetic background: If seeds are from a well-established strain, such as O.G. Kush, Bubble Gum, or a cross-breed, the genetic background should be stated.
- Blend: The blend represents the percentage of the three species — sativa, indica, and ruderalis. All auto-flower strains contain some percentage of ruderalis, which is responsible for the auto-flowering nature of the plant.
- Yield indoors: The number of grams of bud per square meter of plant when grown indoors.
- Yield outdoors: The number of grams of bud per plant (after drying) when grown outdoors.
- Plant height indoors: Shorter than when grown outdoors.
- Plant height outdoors: Taller than when grown indoors.
- Time to harvest: Approximate number of weeks after germination the flower should be ready to harvest.
- Potency: Percentages of CBD and THC.
- Effect: The type of experience you can expect when consuming product from the plant.
Know the laws about buying cannabis
- In some European countries, laws prohibit growing cannabis, but seed is legal, which is quite confusing. You’re allowed to buy and eat cannabis seeds because they’re non-psychotropic, but you can’t buy them to grow cannabis. Other countries in Europe, such as Germany, have their own seed laws.
- In Canada, where cannabis is federally legal, seeds can be shipped across provincial lines.
- In the U.S., in some states in which cannabis is legal, you can purchase seeds from some dispensaries or other locations to grow plants as long as you keep them in the state. Other states may bar selling to non-licensed growers. Shipping or transporting seeds across state or international borders is illegal, although a few reputable online seed stores ship to individuals with success.
Cuttings are typically treated in a similar manner as seeds in legalized locations. They may be available from some dispensaries or outlets for pick up or delivery with a fee. They’re prohibited from crossing U.S. state lines or international borders. You can buy individual plants and mix and match strains. Prices vary and are often determined by plant size.
Buy cuttings (clones) only from a reputable source who understands proper back-crossing of strains for stability. Back-crossing involves pollinating a plant with one of its parent plants to promote sexual stability, so that when you have a female it won’t hermaphrodite into a male during flowering.
Both seeds and clones are often able to be purchased from commercial locations already in your state.
In the U.S., transporting any part of the cannabis plant over state lines is illegal. This applies to seeds and clones and, technically, even to tissue samples.
How to germinate cannabis seeds
Germinating seeds requires a dark environment that is around 70 degrees. There are many ways to germinate seeds (in soil, in a wet paper towel, in starter plugs) You can also sow them directly into soil in a garden or container, as long as the soil is light and fluffy, so the roots can easily grow down and the stalk can break through the soil. Plant the seeds about 1/4- to 1/2-inch deep and cover them loosely with soil.
Most importantly, seeds need a moist environment; they won’t germinate if they get too dry. You can use a heat mat to increase the success of germination in colder climates.
How to transplant marijuana plants
When transplanting any plant, whether it started from seed or a clone, handle it gently, being very careful not to damage the roots. Center the plant in the pot, and plant it deep enough to cover the root ball completely in soil. If the plant is root bound, you can gently tease the roots apart to encourage outward growth.
Pack your soil or other grow medium down around the roots well enough to support the plant while new roots grow, but not so tight that the soil restricts outward root growth. Water the soil around the roots.
About This Article
This article is from the book:
About the book authors:
Kim Ronkin Casey has been a communications professional for more than 20 years and recently took a year-long leap into the world of cannabis as the communications manager for one of the leading dispensaries in North America. She now consults for companies in the industry on internal and external communications. Joe Kraynak is a professional writer who has contributed to numerous For Dummies books.