How much do Cannabis Plants stretch during 12/12 Light Cycle? (2023)

What you need to know:

  • When you switch to 12/12 light cycle, your plants will stretch
  • Stretching continues through the first 2-3 weeks of flower cycle
  • Your plants will double or triple in height
  • Your must get this under control or there will be harsh consequences
  • Use trellis netting to control the height
  • Defoliate early in flower to control the bush

Read on for in-depth instructions….

Welcome to the art and science of Cultivating Cannabis indoors

If you are new to growing cannabis, then welcome to the club! Those of us that grow weed are a small, but growing, community around the world that love the herb. Some of us grow commercially, some us of are caregivers, some of us are average Joes and Janes who grow at home. What we all have in common is a love for the herb.

Growing cannabis used to be extremely underground due to the criminal penalties and harsh consequences of getting caught. Therefore, knowledge and information was shared only in really small circles. With the increasing acceptance and legalization of cannabis, in the United States and around the world, more and more people are getting into cannabis, and more and more professionals are opening up and sharing information.

Which is exactly what we want to do here at Smokey Okies Cannabis. We want to share what we have learned so you can save yourself from making the same mistakes that we did when we first got started in the cultivation game.

In this article, we will address the question of how quickly and how much your plants will stretch when you change the light cycle to a 12/12 flowering cycle.

The difference between Vegetative and Flowering Light Cycles

As we explain in our series How to Grow Indoors, cannabis is a photo period plant, with two distinct phases of growth: the vegetative phase, and the flowering phase.

During the vegetative phase, the grower provides much more light than darkness, such as 18 hours of light, and six hours of darkness. There are many variations, such as 20/4, or keeping the lights on 24 hours a day.

With all of this light, the plants grow, but remain immature. This excessive amount of light will not allow the plants to bud, to develop the “fruit,” i.e. the nugs that we cherish.

In order to trigger the flowering period, the light must be reduced down to 12/12, or some variation of equal or great darkness to light ratio, such as 11/13, etc.

This extra darkness allows the plants to recover, and prepares them to start blooming, similar to the changing of the seasons from Summer to Autumn.

This extra recovery time from 12/12 light cycle causes the Post-Veg Stretch, where plants will double or triple in Height.

This is what you need to know: after you have “flipped” you plants from veg to flower (by switching the light cycle to 12/12), you plants will shoot up in height. Do not be surprised to see impressive growth after 4 or 5 days.

Not only will they have growth spurt that makes them taller, they will also bush out, with the number of fan leaves multiplying like crazy. By the second week, the plant can become wild and crazy if not tamed.

In the first 2-3 weeks, you plants will double, and eventually triple, in height, though this ultimately depends on the cultivar itself. Some strains are known for stretching into pure vines, while others will bush out and just get hairy. Many do a combination of both.

Both Sativa and Indica plants stretch during the first three weeks of 12/12 light cycle

Here is another hint: beware of the myth of sativa vs. indica growth characteristics. If you’re not familiar, the old tale goes like this: sativa plants grow tall, with long intervals between node spacing, and skinny fan leaves, while indica plants grow in a short, bushy pattern.

While both of these growth patterns absolutely exist, they are not limited to these distinct categories of sativa and indica. You will find that a strain that is supposed to be indica dominant may grow extremely tall and vice versa. So know that these patterns exist, but beware that thinking that your plant will automatically be one or the other based on the categorization of its lineage as a sativa or indica.

Regardless of the lineage, it is guaranteed that your plant will stretch during the initial switch to flower, even though the amount of stretching may vary strain to strain.

Now that you are aware that your plant will at least double in height during the first two weeks, what else do you need to know to ensure a good outcome?

You must control the stretch and the over-growth to increase yield potential and avoid problems later in flower

There are several reasons why it is important that you take control of the situation immediately. One, you do not want your plants growing into your lights. Two, you do not want overgrowth to prevent light penetration through the canopy. And finally, you want to control the thickness of the bush to prevent other problems with mold and mildew potential.

There are ways you can control and tame this plant all while it continues to grow and stretch like crazy.

The best tool to use for this is trellis netting, although you can use bamboo sticks or other stakes and attempt to tie the plant down.

But with trellis netting, you can weave the vine through the netting and achieve the most desired method of indoor flowering, which is to create a Screen Of Green (SCROG). Why, you may ask?

When flowering cannabis indoors, you want to create a horizontal canopy to increase your yield.

Your plants are stretching, and that is a healthy sign, but you must control the situation or it will control you. Unless you want minimal yield, you cannot let them grow tall and skinny. You must train them to grow wide, horizontally, and there are several ways to do this.

Prepare your plants during the vegetative phase

First, it all starts in veg. Early in veg, you should top your plants. Topping causes the plant to fork. Topping can be done multiple times in veg which will divide long branches and start the process of training your plant to grow horizontally instead of just straight up.

Continue your training during the flowering stage

Next, you take that topped plant into flower, and as those vines stretch, you tuck them back under the trellis. Imagine a tall, skinny branch, that is sticking straight up vertically. Imagine laying that branch down, by grabbing the very top, and pulling down sideways and tucking it several squares away from the square it is originating from.

The top of that branch is now pointing sideways… at this very moment. Come back in a few days and it will be pointing up, wanting to stretch vertically from the square it is in. What’s more, further down the branch, nodes that would never have gotten any attention are now on top of the squares, and are pointing up as well.

Each of these nodes now has the potential to be a separate cola. By simply laying over a single branch, you created three or four new colas. Imagine if you do this with multiple branches. Do you see the value in Topping your plants during veg?

By weaving the vines through the trellis, you are able to create a wide canopy, which will greatly increase your yield, as opposed to growing a tall, skinny plant.

Take control of the stretching to increase your yield at Harvest Time

When you increase the square feet of your canopy, you maximize your yield with the existing light. This is very important as you are not increasing energy expenditure. You are making use of light that is already there! This can and should be done whether you are growing on tables in a room, or inside a grow tent.

In addition to using trellis to create a wide canopy, you must also defoliate your plant. This will help you achieve a better outcome for several reasons.

Defoliate early in flower to maximize light penetration and remove plant material that has zero potential to become dense bud.

Along with the stretching that occurs early in flower, you plants will bush out and be consumed in fan leaves and plant material.

Do not be fooled into thinking that every node and top that appears will yield smokable flower for your enjoyment. Quite to the contrary, most of those little nodes below the top half of the plant will struggle to fully develop. Those that do will amount to fluffy larf, will weigh nothing on a scale, and will lack the qualities of fully developed and mature buds that make up the larger colas near the top.

What’s more, is that this messy bush, which is preventing light penetration anyway, has the potential to restrict airflow, and can contribute to conditions that support mold and mildew.

It is best to simply remove it all by defoliating your plant.

We have found a best practice in performing a heavy defoliation of the entire plant in Week 2 and Week 4 of Flower. Additionally, we also remove all of the small branches that are in the bottom half. These will never amount to anything, and they merely suck energy from the upper half of the plant.

By removing all of the inner fan leaves, you open up the canopy for new growth, new branches that can then poke through the canopy and become colas. You also allow light to penetrate and grow the nodes that are just below the surface of the canopy.

You shave everything off down below, and you have now set yourself up for success in maximizing the yield of your plant during the second half of flower.

If you’re interested in learning more about growing indoors, be sure to check out our blog. Don’t forget to subscribe to our newsletter.


How much will my cannabis plant stretch? ›

How Much Do Cannabis Plants Stretch During Flowering? All plants will stretch to some degree during the flowering stage, and you shouldn't be worried, even if it's quite a lot. Some strains will double in height in a matter of days.

How much will a plant stretch during flowering? ›

The flowering stretch. This usually occurs in the first two weeks of bloom and is when the plant shoots upwards. In some strains, it may almost double its height before it focuses on producing the bud. Since larger plants will often produce more buds, most growers want to encourage this stretch period.

When should I switch to 12 12 light cycle? ›

Height of plant: Depending on the strain, plants will generally double in size during flowering. So, if 'room' height is limited, the switch to 12/12 will need to be done no later than when the plant has reached 50% of the 'available' height (remember to consider the minimum gap distance between lamp and foliage).

What is a 12 hour light cycle for cannabis? ›

During this stage, 12 hours of full-spectrum light and 12 hours of darkness are recommended. This cycle is mimicking the sun's natural exposure and cycle during the transition experienced in fall. During this time the plants' buds will grow in size, the pistils will darken, and trichomes will become whiter.

Does cannabis stretch at night? ›

Plants will naturally grow towards the light and in low light situations they will elongate and stretch to reach the illumination they crave, leading to spindly and lanky plants with weak stems.

What week do cannabis buds get bigger? ›

The last three weeks is when your buds can actually gain the most weight – that is if you feed them Overdrive®. After your peak bloom phase, your plants enter their late bloom phase (the precise timing and length of which depends on the strain of cannabis you're growing).

What will make buds bigger during flowering? ›

The bigger the leaf area, the bigger your buds will be. Nitrogen is the nutrient needed most for this green growth. When plants reach their mature size and begin flowering, they need more phosphorus, the nutrient most essential for budding.

How do you yield bigger buds during flowering? ›

You want to vent the humid air as much as possible and replace it with fresh air. The important thing is to keep the air moving around your plants as much as possible. Proper Temperature – You want to keep temperatures warmer than 68°F (20°C) (to avoid diseases like bud rot) but no higher than 80ºF (26.6ºC).

How do you stop stretching during flowering? ›

One of the easiest ways to reduce stretch is to maximize the amount of light plants receive. Providing adequate spacing, reducing the number of overhead baskets/containers and installing new or cleaning the existing glazing can help to prevent overgrown plants. Dirty glazing can reduce light levels by 20 percent.

Should you water more or less during flowering? ›

Generally, you want to water every 2 or 3 days during Flower and you want to water enough that 10-20% of water comes out from the pot as runoff. You can check your soil moisture by sticking a finger in the pot: if the soil is dry a couple inches down, then it is time to water again.

Can you grow autos on 12 12? ›

Some growers still decide to keep their autos under a 12/12 light cycle during flowering. And that's fine, as autos grown in these conditions can still produce a fair harvest. Just remember that the buds you harvest under a 12hr light cycle will be noticeably smaller than what you'd get under a 18–24hr cycle.

Is 12 hours of light too much for plants? ›

' plants do require a daily respiration period of at least 6 hours per day (for seedlings) and ideally 8-10 hours for more mature plants. Therefore we do not recommend providing more than 14-16 hours per day of light, even if you are growing long-day-loving varieties and trying to induce flowering/fruit from them.

Does more light mean more yield cannabis? ›

Light Intensity and Yields

The light intensity rule of thumb is that a 1% increase in light equals to a 1% percent increase in yield.

Does flowering time start at 12 12? ›

Counting from the day you flip to 12/12

After all, this is the point at which the plant gets the cue to start flowering, so it's a simple point of departure. The issue with this method is that—at least externally—the plant may not appear to begin flowering immediately.

Will cannabis flower with more than 12 hours of light? ›

The critical night length, or the amount of time required for the photoperiod response in Cannabis to occur in order to stimulate flowering, is between nine and 10 hours, which corresponds to 14 to 15 hours of daylight, but it varies by cultivar.

What is the lowest nighttime temperature for cannabis? ›

This triggers plants to move out of vegetative development and into bloom. The ideal daytime range in flower should be between 72 and 85°F, while the room can drop to as low as 55 to 70°F at night.

What makes cannabis stretch? ›

Stretching in reference to cannabis is a term used to describe sudden, upward growth. It can happen because of environmental stress, genetics, or a combination of the two. Generally, stretching has a bad rap when it comes to growing weed. And though it is often a sign that something is awry, this isn't always the case.

When should you cut off fan leaves? ›

Usually, growers trim the fan leaves weeks before harvest, which is a period that leads to senescence, a phase in the plant cycle when the larger leaves start fading away. It is safe to start removing these dying leaves and continue until harvest.

What week do buds get sticky? ›

Late flowering / Ripening stage – week 6 to harvest

They are sticky to the touch and can be very smelly. You are very close to reaching your goal = harvesting! Most importantly, buds are now covered in trichomes, which are rich glandules for secreting THC and other cannabinoids.

What is the last week of flower for cannabis? ›

In this article, we're covering your cannabis in late flower, which is typically weeks six to eight of your bloom cycle (with the final week being your flush week). This is the period when you're going to ramp up terpene and cannabinoid production and add some serious potency, flavor, and weight to your flowers.

Do buds fatten up during flush? ›

When the flushing process has reached the fan leaves, they will begin to yellow and turn lighter as they send the stored nutrients to the flowers. The flowers will fatten up during these last few weeks while flushing; this can be up to 25 percent of the final weight.

How do you get big thick buds? ›

To some degree, more light translates to fatter buds and higher yields (you'll need to pay attention to the distance between your grow light and plants or your plant may suffer from light burn). Increasing light intensity is the most effective way to fatten up buds.

What makes buds fluffy? ›

These airy flowers are often the result of suboptimal growing conditions, a lack of light, or nutrient deficiency. Fluffy buds don't only look less appetising, but you'll need to use more of your harvest every time you roll a blunt or hit a bowl.

How do I make my buds tighten up? ›

A bud hardener is an additive you can use at the end of the flower cycle to tighten up your flowers and pack on weight. They are typically used in the final 3 weeks or so of the grow cycle and contain a mix of macronutrients, micronutrients, minerals, essential oils, etc.

Does Epsom salt help flowering stage? ›

Adding Epsom salt is a simple way to increase the health of their blooms, and is something that you can include easily as a part of a normal routine. For potted plants, simply dissolve two tablespoons of Epsom salt per gallon of water, and substitute this solution for normal watering once a month.

Should I use Epsom salt during flowering? ›

Yes, there seem to be good, relevant reasons for using Epsom salts for plants. Epsom salt helps improve flower blooming and enhances a plant's green color. It can even help plants grow bushier. Epsom salt is made up of hydrated magnesium sulfate (magnesium and sulfur), which is important to healthy plant growth.

What should my buds look like at 5 weeks? ›

In week 5 of flowering, you can observe the buds all over your plant becoming thicker. You may also spot new buds growing in new places such as along the main cola. With buds abounding, your cannabis plants will get fatter every day. This is a surefire sign you are in full flowering mode.

How often should I feed during flowering? ›

The nutrient requirements will change dramatically when the plants enter the flowering stage, and this may be a little hard for new growers. You can feed your plants 1-2 times every week, gradually increasing the nutrients, but at the same time pay attention to your plants' reactions after each feeding.

Should I feed every watering in flower? ›

For soil growers, plants can be fed once every second or third watering. If plants are fed with every watering then nutrient buildup and lockup becomes a problem causing stunted growth, “crows foot” (curling downwards of the leaves), leaf burn, deficiency symptoms, burnt and damaged root system and decreased yields.

What happens when you water a flower every day? ›

Overwatering, however, increases the risk of root rot and fungal disease. If you see droopy stems, wilting leaves, a whitish coating (fungus), or fungus gnats in the home—pests that thrive on consistently wet soil—it's a good bet that you're watering plants too much.

What is the best light cycle for flowering stage? ›

The flowering phase in Cannabis is triggered by the light/dark cycle. It is started by changing your cycle to 12 hours on and 12 hours off. During this phase, the plants will continue to grow vigorously and require even more light because of their size.

What is the longest an Autoflower can take? ›

Fast growing autoflower seeds can also be extremely potent! Some of the heaviest yielding autoflower strains can take up to 15 weeks from seed to harvest.

Can you veg in 12 12? ›

With 12 12 from seed, you effectively skip the veg period and get right into flowering. Contrary to the name, you rarely will actually put your plants right into a flower photoperiod, though. It's commonplace to start seeds and let them develop a few sets of true leaves before initiating flower.

Do plants grow faster with constant light? ›

Light is an essential factor in maintaining plants. The rate of growth and length of time a plant remains active is dependent on the amount of light it receives. Light energy is used in photosynthesis, the plant's most basic metabolic process.

Do plants need a dark period? ›

Plants, shrubs and trees use sunlight for photosynthesis during the daytime, but at night they need darkness to regenerate a key compound - phytochrome. Nighttime lighting can reduce vegetation's ability to properly create this compound.

Can you overdo grow lights? ›

But can too much light kill a plant? In extreme cases, the high light intensity can cause severe enough damage to your plant that it eventually dies. It can also dry it out, making it difficult for the plant to undergo photosynthesis and proper growth.

What is the best light cycle for cannabis? ›

For indoor grow rooms, plants should be kept on an 18-hour day light cycle with a 6-hour night period. You can keep your plants on a 24-hour light cycle but plants tend to do better when given breaks and it will save you some money.

How do I know if my cannabis plants are getting too much light? ›

Leaves will start to turn brown or yellow when they are experiencing light burn from too much light or heat. Light burn can make the leaves hard and crisp and gives them a burnt appearance. Overexposure can happen if the lights are too close to the canopy and the temperature is too high.

What light intensity is best for cannabis? ›

What is the Best Light Intensity for Cannabis? Experts recommend at least 1800 micromoles for the hemp plant. At this level, you are likely to get the best value for your plant. After you hit 1000 micromoles, a 1 % increase in the light intensity translates into a 1% increase in yield.

How long into flowering will I see pistils? ›

Autoflowering varieties usually start to develop their first pistils around weeks 3–4, whereas photoperiod strains will produce them shortly after the grower reduces the light cycle indoors, or when the seasonal light cycle decreases outdoors.

How many hours of dark does it take to start flowering? ›

When you are ready for your cannabis plants to flower, a 12-hours of light and 12-hours of darkness schedule is standard. Nighttime provides darkness, keeping cannabis on somewhat of a natural clock.

What does week 1 of flowering look like? ›

Week One. Week one is the transition stage between pre-flowering and full flowering when your plant switches from growing tall to producing buds. During this transition, some strains will double in height from what they were a week earlier. Because of this rapid growth, week one is commonly known as “the stretch”.

How long after switching to 12 12 will I see buds? ›

So in summary, you will not see buds for the first three weeks. During the third week, pre-flower sites will emerge, but will not fill in until Week 4. You will notice distinct development in Week 5 that will only increase as the plants progress through the remainder of flower.

Do cannabis buds grow more at night? ›

Photoperiod cannabis is sensitive to changes in the hours of daylight it receives. In fact, photoperiod cannabis strains cannot transition from vegetative growth to flowering without long nights. 12 or more hours of darkness is the biological trigger for photoperiod cannabis to bloom.

How many hours of light does cannabis need during vegetation? ›

The vegetative light cycle of cannabis is when plant growth truly takes off. Much like a human adolescent, the plant will achieve most of its vertical growth during this time. Lasting between 3 to 16 weeks, the vegetative stage requires full-spectrum light for 18 hours and 6 hours of darkness.

How much does a cannabis plant usually yield? ›

Average Yield Per Outdoor Cannabis Plant Grown In Soil

Outdoor marijuana farmers determine yields by calculating grams produced per plant, and the desired range is 600-750 grams. This requires cultivating larger plants compared to indoor breeding plus it depends on consistent sunlight and favorable weather conditions.

Do taller cannabis plants yield more? ›

And a taller plant does not necessarily mean a bigger harvest. In fact, tall cannabis plants can be a sign that they are unhappy—particularly, that they do not have enough light. As well as causing your plants to stretch, a lack of light will negatively impact the size and quality of your final crop.

Will my cannabis buds get bigger? ›

You need to use top-shelf genetics if you want massive buds. You can grow various strains from either clones or seeds. Use bloom boosters – When you give your plant a proven, cannabis-specific bloom booster, you're giving it the extra elements that help it grow bigger, denser, heavier and more potent buds.

Do cannabis plants double in size? ›

In my experience with several different hybrid strains, a good rule of thumb is to generally expect that cannabis plants will double their height after entering flowering. If the plant is growing long and lanky, with thin leaves like a sativa, expect the plant to grow more.

What is the biggest yield from one cannabis plant? ›

Skywalker OG is the highest yielding Marijuana strain, and when grown outdoors, growers can harvest up to 650 grams per plant.

What is the average profit margin for cannabis? ›

Dispensaries typically generate between $1 million and $4 million in annual revenue. Dispensaries typically generate a profit margin of between 10% and 30%

Can I harvest one bud at a time? ›

To answer your question—yes, you can cut the mature buds from the top of the plant and clear the branches and leaves to allow better light penetration to the lower portion of the plant. And the lower buds will continue to grow and ripen and can be harvested a week or two later.

Can too much light stunt cannabis growth? ›

Cannabis loves light and a well-illuminated greenhouse will produce strong, tall, healthy plants with robust buds. It's possible to overshoot the mark, though, and provide so much light that plants end up struggling rather than thriving.

Is topping a cannabis plant better than bending? ›

Topping Cannabis Plants vs Super Cropping

While both approaches may look similar in the end product, the difference lies in the process. Topping employs the complete removal of the apical shoot as the plant stressant, while super cropping only involves pinching, bending, and tying the branches at a specific angle.

How tall should a cannabis plant be when you top it? ›

Plant selection is key when topping your weed plants. Look for a plant that's between two and three nodes tall. If the plant is shorter than two nodes, it may not have enough energy to produce a worthwhile harvest. If the plant is taller than three nodes, it may have too much energy and produce multiple tops.

How do you get super thick buds? ›

To some degree, more light translates to fatter buds and higher yields (you'll need to pay attention to the distance between your grow light and plants or your plant may suffer from light burn). Increasing light intensity is the most effective way to fatten up buds.

How do you get big heavy buds? ›

Grow More Big Buds Indoors
  1. Turn Up The Lights. ...
  2. Change Nutrients for Each Stage. ...
  3. Train Your Plants. ...
  4. Bone Up On Your Feeding. ...
  5. Control Temperature and Humidity. ...
  6. Pump Up CO2. ...
  7. Be Patient.

How do you get thick buds? ›

Increasing the amount of CO₂ in your grow room can help you grow bigger, denser buds. By doing so, you'll help plants photosynthesise faster and encourage them to take up more nutrients and water.

Why is my cannabis plant stretching? ›

Some growers lower greenhouse night temperatures to save on energy costs, while daytime temperatures are warm due to sunny days. Cool night temperatures along with warm sunny days often result in plant stretch. The greater the difference between day and night greenhouse temperatures, the more stretch occurs.

Does longer vegetation mean bigger buds? ›

The vegetative stage of growth determines a weed plant's final size. Once it begins flowering, the energy goes from growing upwards and outwards to produce buds. So the longer a plant vegetates, the larger the final yield can be, in general.


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