How to Prevent and Fix the Stretching of Cannabis Plants?

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Added 13 September 2022

Imagine this scenario — your cannabis plant is already four feet before you switch it to a 12/12 light cycle. But suddenly, the plant starts stretching and reaches over six feet, which is way higher than you expected in your little grow room.

This is called cannabis stretching, which occurs during the flowering phase. And it’s not always a good thing as it can significantly dampen your plant’s yield and make it unfit for your grow room. And in some cases, the plant may break and crash.

But what is cannabis stretching, why does it happen, and how can you prevent and fix it? Read on to know more.

What is Cannabis Stretching?

Cannabis plant stretching

Image Credit - BigDaddyK

Cannabis plants stretch during the vegetative stage, that’s the natural process, but in some cases, they can exhibit a burst of growth during the flowering stage. Again, this is a natural process, but it can be a bad thing if the plant stretches too much. 

Excess stretching of the cannabis plant can lead to tiny, airy buds and relatively lower yields than you would have expected. Plus, if your grow room is limited in space, a stretching cannabis plant can quickly outgrow it, leading to other spatial problems.

Instead, when growing cannabis, you need plants that grow sideways for a healthy yield. In this case, most of the buds get to bask in light while reaping from the plant’s nutritional supply, which leads to higher quality and yield. This is why it is crucial to control your plant’s stretching and not let it do its thing — it might not be suitable for the yield. 

Another problem with stretching is that when plants stretch too much, they can break under their weight, which can compromise your yield. And even if they don’t bend over, they can grow too close to the light and experience a light burn. 

Remember, not all cannabis plants stretch the same way. Some strains stretch more than others — some even double in their height while others may only grow a couple of centimeters. The problem is not the plant growing, it is the plant stretching more than what is ideal for it and your grow room.

Why Do Cannabis Plants Stretch?

Cannabis stretching

There are various reasons why cannabis stretches, which we will get into in a minute, but the most common factor for cannabis stretching is genetics. If your strain is genetically tall and lanky, its seeds will most likely grow into tall and lanky plants. For example, Sativa strains genetically stretch more than their Indica cousins. But you can still control their growth — as shown in the later sections.

Here are a few other reasons why cannabis stretches.

1. Distance Between the Plant and Grow Lights

One of the common reasons why many cannabis plants stretch too much is the distance between the plant and grow lights. This usually occurs indoors, but can also occur outdoors. 

When the grow lights are too far from the plant, the plant does not get to bask in adequate light, which makes it want to grow taller to reach closer to the light source. This can lead to the plant growing too tall, which is known as stretching.

2. Type of Grow Lights

Similarly, cannabis plant stretching is also dependent on the type of grow lights you use. If the grow lights are not adequately intense, the plant may experience a lack of light and stretch further. This can happen if you are using smaller lights for plants.

On the other hand, even the light spectrum plays a role here. If your grow lights are red or orange dominant, even they can encourage the plant to stretch. Thus, simply incorporating more blue spectrum into your grow light can prevent this from happening.

3. Crowded Plants in the Grow Room

Another reason why your cannabis plants may excessively stretch is if you are growing too many plants in a smaller space. Once the grow room gets overcrowded, the plants start competing with each other for resources like light and air, which makes them grow taller and taller. 

How to Prevent Stretching in Cannabis Plants?

Cannabis plant stretching hard

Image Credit - xAK47FULLx 

Knowing what factors influence stretching helps us figure out ways to prevent that from happening. And it’s fairly easy to do. Just follow these steps to control your plant’s growth and prevent cannabis stretching. 

1. Choose the Right Strain

Like many other problems in cannabis plants, even stretching can be avoided by choosing the right strain. As mentioned earlier, cannabis stretching usually occurs due to genetics since some strains are predisposed to growing taller than others. 

So, find the right strains that suit your environment and grow room. For instance, if your grow tent’s ceiling height is six feet, choose a plant that goes around four feet maximum, so you know that even if it stretches, it won’t stretch a lot. 

Also, most Indica dominant strains grow shorter and broader, while Sativa dominant strains grow upwards as they reach for more light. So, if your ceiling space is limited, choose an Indica-dominant plant. 

You can also find your strain’s growing qualities online, usually on the product description page of the seeds. Most reputable seedbanks mention all that you can expect from the plant. But if you want to dig a little deeper, you can participate in community forums to know about other growers’ experiences with growing that strain.

You can also research your strain here on Growdiaries to read reviews from other growers. Know that these resources are not 100% accurate since stretching also relies on other factors, not just genetics. But it is a good starting point. It’s better to choose a shorter plant and control its stretching with minimal effort than a taller plant and work extra to control its stretching.  

And when buying seeds, always choose seeds from reputable seedbanks. Such seedbanks have a set of standards that ensure an optimal level of consistency in their seeds. On the other hand, seeds from unreputable dealers may not be genetically fit.

2. Plan Your Plant’s Growth

Considering your grow room’s ceiling height and the strain’s genetics, the next step is to plan your plant’s growth. What you can do is ensure that the grow room is adequate for the strain you are growing if your strain is likely to grow tall. 

Depending on various factors, like the type of grow lights, ceiling height, container or pot, etc., you will have a rough idea of how tall the plant can grow in your grow room before it is a problem.

Once the plant reaches half of its maximum height, switch to the 12/12 light cycle to force flowering. Cannabis generally stretches during the early flowering stage; however, it rarely stretches more than double its height, so this should be enough.

3. Optimize the Light Source

Since the plants stretch during the early flowering stage, ensure that your grow lights are spaced at the right distance during that time (and other times, too). The ideal distance depends on the type of light you use and its intensity. However, generally, CFL lights are best at a distance of 10 cm, and HID lights are best at 30 cm from the cannabis plant.

But this number can vary, depending on the manufacturer and type of light. So, ensure you pick high-quality lights and follow the manufacturer’s recommendations to ensure the light is intense enough for your plant. This will prevent your plant from stretching too much while looking for more light.

You should also do a hand test to check if the light is too close to the canopy. Place your hand over the plant’s top end with the palm facing down. If your hand feels warm or painful, then the lights are too close to the plant and you should move them slightly up. But this test does not work with LED lights since they don’t heat up a lot.

Another factor that influences cannabis stretching is the light spectrum. If your grow lights are red or orange dominant, the plants tend to grow thinner and taller, whereas blue dominant light encourages the stems to grow thicker and shorter. 

Here, you can use metal halide lamps or programmable LED lights to ensure your grow lights are not only red or orange dominant but also contain the blue spectrum.  

Here are a few points regarding the light type and distance:

  • HPS lights tend to make cannabis plants stretch, and you can deal with this by leaving your MH bulbs as is for the first few weeks of flowering before switching completely to HPS lights.
  • If you are using CFL lights, use vegetative bulbs (6500K) during the first couple of weeks of flowering before switching to flowering bulbs (2700K).
  • Choose LED lights because they offer various benefits including allowing you to control the color temperature and intensity. Plus, they don’t heat up a lot and can last up to 11 years. 

4. Keep the Temperatures in Check

Next up, you need to keep the temperatures in check to prevent your cannabis from stretching. Generally, temperatures over 82°F or 28°C tend to encourage the plant to grow taller. 

You can prevent this by investing in a basic ambient thermometer and checking the temperatures regularly. If the temperature rises over 82°F, use the air conditioner to maintain it under that level.

5. Promote Air Exchange

A good ventilation system that constantly recirculates the air and keeps it fresh can help you keep the temperatures down. In some strains, the wind from ventilation can even make the plant stronger as it acts to protect itself from the wind — like in the wild — although excess airflow is not good for the plant as it can experience a dry-out.

This is especially important in an indoor setup since outdoor plants already benefit from natural air movement. 

6. Force Flowering Early

If you are growing a strain that may grow too tall, or if you think your plant is already growing faster than you expected, you can prevent it from stretching excessively by reducing the vegetative period and forcing it to flower sooner so there is more ceiling space left for it for its final flowering stretch.

If you are growing an autoflowering strain, you can do this easily. Once the plant reaches half of its desired height, switch the light cycle from 18/6 to 12/12 to force it into the flowering stage. This does not work for autoflowering strains since they grow regardless of the light cycle, but they also don’t experience as much stretching since they are inherently shorter plants.

7. Space the Plants Out

You need to ensure that your plants have enough space around them to grow wide; otherwise, they may grow too tall by competing with other plants, in search of more resources. 

Plus, good spacing between your plants also improves air circulation, keeping the plants fresh and dry so they don’t experience mold or other problems.

But if you are planning to grow your plants using the Sea of Green (SOG) method, you can skip this step. SOG needs the plants to be close-by. 

8. Limit the Nutrition and Carbon Dioxide for Your Cannabis

Another way you can keep your plants from stretching is by reducing the fuel that encourages plant growth. Yes, it sounds counterintuitive, but when done right, it can help the plant grow with good health while still avoiding it from stretching.

Cutting back on nutrition and carbon dioxide during the early flowering stretch prevents the plant from stretching too much during this time. But this is not the ideal way to prevent stretching and should be used as a last resort, not the first solution. 

9. Train Your Plants

If you have done everything right but your plant still wants to grow tall, you can train it to grow broader and shorter with some training methods. These methods are manual interventions, where you may have to dirty your hands, but they work well to control your plant’s stretching.

Plus, training methods also have significant benefits for your plant’s health and bud development. When done right, training can help you boost your yield dramatically. 

Training your plant involves manually bending (or cutting) specific leaves or shoots of the plant, which makes the plant focus on healing the trauma than vertical growth. Plus, as an act of self-defense, the plant also starts producing a lot more energy to sustain itself and encourages bud development.

Here are a few plant training methods you can use to train your plants:

  • Low-Stress Training (LST)

LST is a common training method where you just have to bend the shoots of your plant to the sides during multiple training sessions throughout the growing cycle. This not only prevents your plant from growing too tall but also improves the light exposure of the bud sites. 

The main benefit of LST is its optimization of light exposure. When the plant is growing tall, not all bud sites get enough light, which leads the buds on those sites to grow airy and small. But with LST, the light is equally distributed to most bud sites, leading to bigger buds on the plant.

  • Topping

Topping is more severe than LST since it involves cutting specific parts of the plant, but it works on the same principle as LST.

For Topping, you have to cut off the main stalk of the plant, which contains one giant cola. This process breaks the apical dominance in the plant. Topping can not only prevent your plant from growing too tall, but it can also increase your yield. 

  • Screen of Green (ScrOG)

In the ScrOG method, you allow the plant to grow uninterrupted during the vegetative stage, but once it reaches the flowering stage, you place a screen above the canopy and tuck the branches in each of the screen’s holes. 

This method creates an even canopy while restricting your plant’s vertical growth, which keeps the plant short but a lot broader. This further improves the light distribution on the bud sites, leading to bigger flowers around the canopy, not just on the top. 

Some More Tips on Preventing Cannabis Stretching

Apart from the methods listed above, there are a few other things that you can do to prevent your plant from stretching too much. These methods may not always work but can be handy in some cases. Here are some more tips on preventing cannabis from stretching:

  • You can find various products that claim to stop the plant’s vertical growth, like Stop Grow by Pro-XL. Such products may not always work as claimed, but you can check out the reviews to see if other growers have benefited from them.
  • Some growers have also reported that 6-Benzylaminopurine (6-BAP) can also prevent the plant from stretching too much. 6-BAP is a synthetic cytokinin, which many farmers use on their crops to improve productivity and flower set, but this application is difficult to source, complicated to use, and toxic for humans. 
  • You can also try keeping your plant in 48 hours of complete darkness before switching to the 12/12 light cycle. 
  • Some growers have also found that restricting the growth of roots can keep the plants from stretching too much — this can be done by growing the plants in smaller pots for the first month of the flowering stage followed by transplanting them into a bigger pot.

How to Fix Stretching?

Cannabis plant stretching and touching lights

If your plant is already growing too tall, it may be too late to prevent stretching. But all hope is not lost. You can still fix this problem with a few simple steps, such as the following.

Bury the Stem

If your plant has grown too tall, you can simply bury it deeper into the growing medium to bring it down to your desired height. Additionally, you should also add some support from the ground up from the plant so it can retain its shape.

When you are burying the stem, be extremely careful not to damage the plant’s roots. 

Stake the Plant

One of the issues with a stretching plant is that it can bend under its own weight. Here, you can use basic gardening stakes to support the plant. Install one or two stakes into the soil and use gardening ties to tie the plant to the stake. 

When using ties, do not tie them too tight or it may damage the plant tissues or restrict the stem’s growth. 


To take it further, you can also use trellises, either vertical or horizontal. It can also help support your plant, and if you do it horizontally, you can also use it for the ScrOG training method.

You can also use several other training methods, including bending it over and tying it to a trellis or frame to manage its height. Training methods are anyway recommended for growing yields, but in this case, they offer an added benefit. 

Summary: How to Prevent and Fix the Stretching of Cannabis Plants?

Icarus wanted to fly high, but he flew too close to the sun — the sun’s heat melted his wax wings, leading to his demise. Funnily enough, your cannabis plant may be like Icarus — it may reach too close to the sun (read: grow lights), experiencing light burns or bending under its own weight.

Cannabis stretching is a common problem, especially during the flowering stage, and you need to take it seriously. It can be bad for your plant, reduce your overall yield, and perhaps force you to make drastic changes to your grow room so that it can fit, but even that may not always be possible.

So, use the methods mentioned above to prevent your plant from stretching. Remember, stretching is a natural process but with the right timing, growing techniques, and nutrition, you can stop it from being a bad thing. Vigorous growth is good for the plant and its yield. 

And if your cannabis plant has stretched too much already, it’s not the end of the world. There are various training methods, along with burying the plant a little deeper, that can help you manage your stretched cannabis plant. 



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