By Luke Sumpter

Do you want to go from seed to bud quicker and cheaper? A faster, space saving and economical way to grow is the no veg, seed to flower, 12-12 light cycle method.

Growing with a 12-12 photoperiod is a solution to space and resource problems. This method eliminates the vegetation phase of growth and forces the plant to go straight into flower from a seedling. Yields are lower than that of a regularly grown cannabis plant, but results are obtained much faster, with a few advantages.

The 12-12 lighting technique makes the grow cycle 7-9 weeks in general, rather than the much longer time needed when giving plants a vegetative phase. For the space constrained, and those willing to experiment and give it ago, it can be a dream come true.

12-12 Cannabis Light Cycle

What Is 12/12 From Seed?

12-12 simply refers to the hours of light and darkness a cannabis plant is exposed to – 12 of each. Normally, a cannabis plant is exposed to an 18-6 light cycle. This tells the cannabis plant conditions are good for growth, and it focuses on building up size and foliage. When light cycle is changed to 12-12 (either naturally or through human intervention), it tells the cannabis the seasons are changing, and it is time to flower. By forcing a 12-12 light period from the start, the cannabis plant goes directly into flowering, in a bid to reproduce. You are essentially tricking the plant into thinking the growing season is coming to an end, so it needs to produce flowers ASAP.

Know the Signs of Flowering

The first signs of flowering when growing cannabis 12/12 from seed are the flowers themselves. During the early stages of growth, your photoperiod cannabis strain of choice will start putting out leaves so it can create the energy needed for growth. Soon after, it’ll get the message based on the limited light cycle that it needs to start sending out flowers. These will occur at the nodes—the points at which the branches and main stem intersect. They start out as “pre-flowers”, a single bract equipped with small hairs called stigmas. These small structures are surefire signs that your plant has already moved past the vegetative phase. From this point, you can expect your plant to stretch slightly, and for the pre-flowers to develop into larger buds.

Signs of cannabis flowering

The Best Nutrient Strategy for 12/12 From Seed

Under normal lighting circumstances, growers focus primarily on feeding their plants plenty of nitrogen during the vegetative phase to fuel leafy growth. After switching to bloom, they transition to formulas higher in phosphorus and potassium to drive flower development. Growing 12/12 from seed skips the vegetative phase almost entirely, but cannabis plants still need some amount of nitrogen to support healthy growth and metabolism. For the best results, select a product such as the RQS Bio-Grow Fertiliser with a balanced NPK ratio of 3-3-3 to provide an initial balance of all three macronutrients. After 2–3 weeks, switch over to a product with an NPK ratio of 0-5-5, such as Bio-Bloom Fertiliser, to drive flower development in the final weeks of the growing cycle.

How to Grow Cannabis 12/12 From Seed

Growing 12-12 is as simple as changing the timing on your light cycles, giving your plants equal amounts of day and night right from when they sprout. The plants will look different to a cannabis plant that goes through vegetative growth. Photosensitive hormones in cannabis make the highest point the largest cola. This method all but guarantees only main bud growth on every small plant. Essentially you will be growing a cola with a few short, budded side branches – with the plant basically being a bud in itself. Be sure to stake your plants.

Everything to which you would pay attention in a normal grow remains unchanged and are still just as important. pH and water quality, nutrient mixing, pest control, grow medium conditions, EC and ppm all still play their major roles in the dankness and weight of your finished product.

Growing this way still requires all the knowledge that would be needed to flower plants with any other method, and maintenance routines still remain unchanged. After diluted nutrients, while still young, treat your plants as you would during a normal bud cycle. However, flush more often, every ten days at most, so as to avoid salt build-up in the smaller pots.

Done with expert practice and a willing strain of cannabis seeds, it is not unknown to produce 1 gram of ganja per watt of lighting. That’s an impressive 250g in 7-9 weeks for a 250W light in a small cupboard!

The Advantages of Growing Cannabis 12/12 From Seed

Growing cannabis 12/12 from seed offers a wealth of benefits to growers of all experience levels. Check out the main advantages below:

  • Speed: Growing 12/12 from seed skips the vast majority of the vegetative phase. This cuts weeks off of the growing cycle as a whole. You can expect to harvest buds in around 7–10 weeks after your seeds sprout.
  • Maintenance: Plants grown under 12/12 from seed are much easier to take care of than their larger counterparts, which have spent weeks in the vegetative phase. Their small canopies mean growers spend much less time defoliating and training.
  • Size: Building on the above, plants grown 12/12 from seed are much smaller, making them ideal for small grow tents, tiny gardens, and balconies. They’re particularly helpful for growers who prioritise stealth above all else.
  • Cost: Because these plants finish the growing cycle so quickly, cultivators don’t have to run lights as long, which dramatically reduces energy bills.
12-12 Cannabis Light Cycle advantages

Growing 12/12 From Seed to Harvest Saves Space

Plants with less side branching and canopy spread need less space between them, increasing efficiency. As an example: 1x 15-litre pot produces one plant with a large volume and difficult maintenance issues in a cramped space. 4x 3.5-litre pots in the same sized space can produce just as much dried material with the benefit of being easier to rotate, so the whole plant gets 360-degree light. The entire crop is less hassle during maintenance as each plant is 100% accessible and physically easier to move about. There is no need for a separate sprouting and veg space or time wasted on 18-6 vegetation. The seeds can be sprouted under the 12-12 growing lights providing continual flowering plants.

Save on Resources With a 12/12 Light Cycle

There is a lesser demand for resources across the boards.
You will experience only half the water consumption with less moisture loss due to evaporation, and a third less nutrients are used. CO₂ and electricity use including most peripherals are reduced by a staggering 650 grow hours annually.
Taking hours to accomplish, tipping, fimming, branch control, and mainlining are now unnecessary freeing up your most precious resource, time.

Why You Should Keep Things Clean During 12/12

Always be sure to re-sterilize your grow space after each crop.

Keep a keen eye out for moulds and mildews as the grow space will be getting less light with more moulding opportunity in warm dark corners and creases.

Key Tips for Growing 12/12 From Seed

There are some haters of this method, but many love it. Those who hate on it often have not actually tried it. It is all about giving it a go and seeing what works for you. Even if you decide against it after trying it, it all helps expand your knowledge as a grower.

Some sativas will still stretch to 1.2 metres using this method, so species selection right at the very start is key. Indicas are the obvious choice for maximum space saving. They are generally smaller, and 12-12 will keep them very manageable. You will enjoy small pots full of colas, like a miniature stinky forest. Buds grown this way are indistinguishable from vegetated plants in flavour and effects, and at the end of the day, getting buds in the jar quicker and more often is a good thing right?

Using SOG When Growing 12/12 From Seed

SOG, or sea of green, is an ideal technique for those working with small spaces. The idea is to grow many small plants per square metre, optimising yields over a given area rather than per plant. While some SOG growers start plants under a 12/12 schedule from seed, others allow the plants to veg for 2–3 weeks (under 18 hours of light or more) in order to gain a little bit of mass, and hopefully develop more abundant canopies, before switching to bloom.

Cannabis SOG technique

Cannabis 12/12 From Seed: Lighting and Cost 

A 12/12 light cycle from seed cuts down on energy costs considerably. The cost of a 12/12 grow will vary depending on the power of the light you choose to use and the surface area you need your lamp to cover. You can use the simple formulas below to calculate how much you can expect to spend on this type of grow. First, we need to figure out the running costs of your grow light by pinpointing the number of kilowatt-hours using the following equation:

Numbers of hours running × (watts/1000) = kilowatt-hours

For example, let’s say you choose to use a 200W lamp for a single plant and run it for 12 hours a day for 8 weeks. This gives us the following equation:

672 × (200/1000) = 134.4kWh

Next, you’ll need to multiply your kilowatt-hour figure by the local cost of electricity per kilowatt-hour. For this example, we’ll go off the European average of €0.2 per kilowatt-hour, giving us the following equation:

134.4 × 0.2 = €26.88

Clearly, growing 12/12 from seed will save you a bunch of money compared to the standard price of running your plants through the vegetative phase beforehand. Keep in mind, though, that costs will vary widely depending on the size of the space you need to light and the power of the lights you use.

12-12 cannabis light cycle cost

The Best Cannabis Varieties When Growing 12/12 From Seed 

There are hundreds of different strains available that are perfectly compatible with growing 12/12 from seed. Those that belong to the following categories are the best for this style of cultivation:

  • Photoperiod indicas: These strains have a compact structure, deliver potent buds, and boast brief flowering times. They bolt through the growing cycle while remaining easier to manage than their sativa counterparts.
  • Autoflowers: 12/12 lighting won’t change how quickly autoflowers begin to bloom, as they’re not sensitive to light in the same way as photoperiods. However, the 12/12 light cycle for autoflowers will drastically reduce running costs. Their compact nature makes them ideal for tight spaces.
  • F1 hybrids: These strains are new to the world of weed and have won the hearts of many growers with their rapid growing times, high THC concentrations, and pest and disease resistance. Most F1 hybrids available are autoflowering and therefore won’t flower straight away under 12/12 conditions. However, this method will make growing some of the best strains out there much cheaper.

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