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What to do If Your Cannabis Plant Grows Too Tall?

Added 9 June 2023

On the internet, in movies, and your friend’s house, you have always seen cannabis plants growing small and bushy. Expecting the same, you decide to pop a seed in a container, and a couple of months later, the plant has grown, and it has grown big. 

Now, that’s a great problem to have, though, right? We all want huge plants because they guarantee monstrous yields if you take good care of them. However, not everyone wants a tall plant. 

Your plant has grown way taller than you expected, but should you be worried? If yes, why should you be worried, and how can you fix a cannabis plant growing too tall? Learn all about managing your plant’s height in this article below. 

How Tall Should Your Cannabis Plant Grow?

How Tall Should Your Cannabis Plant Grow?

When growing cannabis, you must know how tall your plant should grow because, otherwise, it can create problems. To do that, you must focus on a few factors that can affect your plant’s growth, starting with genetics, light exposure, and your grow room structure. 

The primary factor here is your plant’s genetics and the strain you grow. Some strains are genetically designed to grow tall, whereas others are not. So, your strain’s phenotype information should give you a rough idea of how tall you can expect your cannabis plant to grow. 

The next factor is light exposure. Have you ever noticed how the buds at the top are the biggest compared to the ones at the bottom of the canopy? That is because the top-tier buds get the most amount of light. Cannabis plants naturally grow towards the light, so if you give adequate light, they will grow tall, but if the light is placed too far or is too weak, they may grow taller to reach closer to the light

The third factor is how far you allow your cannabis plants to grow, depending on your grow room setup and height. If you have a massive grow room, you can allow your plant to grow as tall as you want them to, but in a grow tent, you may have to switch them to flowering if they start outgrowing the tent. 

So, how tall should your cannabis plant grow? There is no single answer — it depends on genetics, lighting conditions, and space. With these factors in mind, you can figure out the ideal height of your plant. You most likely already know this, but what if your plant starts growing taller than you expected? It could be problematic. Let’s learn about why your plant may be growing too tall and how it can be an issue. 

Why is My Cannabis Plant Growing Too Tall?

Why is My Cannabis Plant Growing Too Tall?

Imagine this: you expect your plant to grow five feet tall, but it ends up growing way taller than that. That’s not a good thing, but it can happen for a few reasons, some of which we have already hinted at in the above section. Let’s take a look at the reasons why cannabis plants can grow too tall, which are as follows.

1. Genetics 

If you have purchased non-branded seeds or popped bag seeds, chances are you won’t know the plant’s characteristics from the get-go. In such cases, if you think your plant is growing too tall and all the environmental parameters are ideal, the most likely reason could be genetics. 

So, while you may expect a typical cannabis plant to grow a certain height, the plant you may be growing could be one of the taller strains. This is why reputable seed banks mention the average height of each strain they sell and why bag seeds or non-branded seeds can often surprise the grower with unexpected phenotypes. 

2. You Let the Plant Vegetate for Too Long

Photoperiod cannabis plants rely on the light cycle to switch from the vegetative to the flowering stage. So, the longer you keep the plant in the vegetative stage, the larger it can grow. It’s better to research the characteristics of your strain and switch your plant to flowering at the right time. More on this below.

3. The Grow Lights are Situated Too Far

The above reasons are not really problems since they are generally related to the grower not understanding their plant fully, but placing the grow lights far away from the plant is a problem that needs to be rectified. Your cannabis plant can grow too tall and lanky if the grow lights are a little too far from the plant’s canopy. 

When the lights are situated at the wrong distance, the plant may not receive adequate light, and as a result, it may stretch to get closer to the light sources. This problem is common with LED lights since they are generally placed farther than other light sources like HIDs or CFLs. 

4. The Grow Lights are Too Weak

Similarly, if you are growing a big plant but are using grow lights that are not sufficient to supply the plant with enough light, your plant may grow too tall and thin. This is because the plant thinks the light is situated too far and tries to get “closer” to it, not realizing that the light is just too dim. 

5. The Light Throw is Uneven

Another common reason why some cannabis plants tend to grow too tall is if the light throw is not even, even if the grow light is adequately bright and installed at the right height. This usually happens when the light focuses on the center of the canopy, making it grow taller than the rest of the plant. 

6. The Grow Lights are Red-Spectrum Dominant 

In an outdoor environment, cannabis plants vegetate during the spring and summer seasons when the sunlight is strong, containing blue and white light. As the sun weakens over autumn, the light spectrum gravitates towards red. So, if your grow lights are not on the right spectrum, your plants may start stretching.

But why is that? Because if the light is red-dominant, it contains less blue and white light, which is what your plant needs. Your plant does not get enough of the right type of light — in a way, it is not receiving enough light. Hence, it starts stretching

7. Nutrient Imbalance

Cannabis plants need a good balance of all nutrients, including macro and micronutrients. Many growers experiment with NPK (nitrogen, phosphorus, and potassium) ratios to give the plant exactly what it needs during the vegetative and flowering phases. 

Typically, cannabis plants need more nitrogen during the vegetative stage as nitrogen helps the plant build robust leaves and stems. However, there’s a problem if you overdo it. Just like the plant struggles with a lack of nitrogen, it can also have issues if there’s too much nitrogen. So, if you add too much fertilizer containing nitrogen or use nitrogen-heavy soil, the plant begins to grow too tall. This is because nitrogen not only results in the plant developing elongated stems but it also increases the gap between nodes, which is not good if you’re looking to get big bushy buds. 

8. Temperature and Humidity

The environmental conditions around your plant, including the temperature and humidity, also play a huge role in how it grows. If the temperatures are too hot, the plant starts elongating rapidly to cool itself down. This mechanism is nothing but the plant reacting to stress. Similarly, if your grow room has very low humidity levels, the plants can become taller than expected as they need to increase their surface area to transpire. 

9. Inadequate spacing

Always plan ahead so you know exactly how many plants your grow room can accommodate. Many growers have the habit of growing too many plants in small grow rooms, thereby forcing the plants to compete with each other for resources like light. When the plants sense that they are overcrowded and short of light, they grow taller in an attempt to get more light. Therefore, try to provide enough space for the plants to grow so there’s no need to compete. This way, you can prevent them from stretching and allow them to grow to their full potential. 

10. Light Leaks

Photoperiod plants rely on light to flower. While the plants need an 18/6 cycle during their vegetative stage, growers switch them to a 12/12 cycle to trigger flowering. This means the plants get 12 hours of light and 12 hours of darkness, but it’s incredibly important that it’s completely dark, or they will revert to their vegetative stage!

Even small leaks in the grow room can confuse the plants and interrupt their natural life cycle. Apart from reverting to their vegetative state, the plants can also grow spindly and tall if there are light leaks. Thus, invest in a good grow tent so there are no light leaks. 

What Happens If My Cannabis Plant Grows Too Tall?

What Happens If My Cannabis Plant Grows Too Tall?

As mentioned earlier, cannabis plants can grow excessively tall for various reasons, but some of them can spell disaster for your plant if not fixed on time. Here are some ways cannabis plants that grow too tall can face problems over time. 

1. The Stems May Turn Weak

If your plant is growing, but it doesn’t get enough light, it will stretch to get closer to the light, and in this process, it won’t have enough time or energy to develop a strong, sturdy stem. Due to this lack of rigidity and additional height, the plant may not hold itself up, especially when it starts developing buds. If it gets too heavy, the plant may bend over or topple. 

2. Your Plant May Experience Nutrient Deficiencies

You know that an imbalance in nutrients or excess nitrogen can cause cannabis plants to grow tall. On the other hand, the plant can experience further nutrient deficiencies as it grows taller. This is because the plant will spend a lot of its energy stretching and holding itself up; this can cause other parts of the plant to not get enough nutrients, leading to nutrient deficiency in the plant. The nutrients that could’ve been used for bud and trichome development would now be used to grow taller. 

3. It Can Outgrow Your Grow Room or Tent

If you’re growing your plant indoors, and it starts stretching too much, it can quickly outgrow the space. It won’t grow to the ceiling — in most cases — but it won’t leave enough room for the grow lights and other peripherals on top of it. You will have to prune it heavily to get its size under control, which can be significantly stressful for the plant.

4. Your Plant can Experience Light Burns

If your plant is growing too tall, but the light is located at the right place and is of the right intensity, it can get too close for its own good — it can experience light burns, leading to various other problems in your plant. 

5. Your Plant can Experience Environmental Stress

When your plant gets too tall, it can absorb too much heat from the grow light, releasing more heat into the air. This cycle continues until the grow room heats up too much, causing heat stress to your plant. At the same time, a plant that’s too tall may not experience the best airflow and ventilation, which may risk mold or pest infestations. 

6. Your Plant Will No Longer Be Discreet

Lastly, there’s a reason several growers prefer smaller plants when growing outdoors. They don’t want to advertise to the world that they are growing cannabis due to legal reasons. So, if you're trying to grow cannabis discreetly, a tall plant can outgrow its surroundings and act as a beacon to let your neighbors know you are doing something funky. This may not be a problem in regions where cannabis is legalized, but in other regions, this can invite a lot of trouble. 

How to Control Your Plant’s Height During the Vegetative Stage?

How to Control Your Plant’s Height During the Vegetative Stage?

In most cases, you will notice your plant is growing taller than it should right during the vegetative stage. Fortunately, this is also the best time to control its growth since it can take some stress and damage and still recover before the first flowers start showing up. So, follow these tips to control your plant’s height during the vegetative stage.

1. Use Low-Stress Training like Bending

One of the easiest ways of controlling your plant without using any chemicals is using low-stress training, where you must train your plant to grow horizontally instead of vertically. And unlike your dog, you won’t have to keep giving your plant treats to train it. Follow these steps to train your plant:

  1. Get yourself some soft plant ties and pruning scissors 
  2. When your plant has at least three nodes on the stem, gently bend it down horizontally — ensure it does not snap or break 
  3. Secure the stem using plant ties 
  4. Over time, your plant will still grow taller, so keep securing the stem in the same manner to maintain an even height 

Low-stress training like bending can not only rein in your plant’s height but also help improve light penetration within the canopy, boosting your plant’s overall yields.

2. Top Your Plant 

Another training method you can use to rein in your plant that’s growing too tall is topping, but since this is a slightly stressful method, it is recommended for healthy plants that won’t benefit much from bending. 

In this method, you basically cut the tip of the main stem, which forces the plant to grow wider and not taller. It can also improve your yield significantly as it breaks your plant’s apical dominance and introduces more than one dominant cola. Follow these steps to top your cannabis plant

  1. Use some alcohol to disinfect your pruning scissors 
  2. When your plant has at least four nodes, use the pruning scissor to snip the tip of the plant — make sure you make the cut at a 45-degree angle to prevent diseases due to water pooling

Once you have topped the plant, your plant will develop two main colas, and it will start growing wider. It may still grow taller, but not at the same rate — problem solved.

The above-mentioned method is the conventional topping method, but you can also try pre-flowering topping, where you top the plant just before it enters the flowering stage. This can stop your plant from stretching during the early flowering stage and force it to use the energy to produce buds. 

So, during the pre-flowering stage, start topping all the branches on your plant — you can go as far as topping half of the plant’s mass — and switch the light cycle to 12/12 post-topping. This may reduce the yields, but is a useful technique if your plant has grown too big and has run out of room, and don’t worry, your plant can handle this method as long as it is healthy.

3. Use the ScrOG Method

If bending is insufficient and topping seems excessive for your plant, you can use the screen of green (ScrOG) method — a low-stress training that promises terrific results. This method forces your plant to develop an even canopy that receives equal amounts of light and better airflow, which results in a controlled height as well as much better yields. 

Follow these steps to use the ScrOG method to control your plant’s height:

  1. Get yourself a mesh screen with wide holes, a wooden frame (or similar), and gardening ties 
  2. Attach the screen to the wooden frame and suspend it just above your plant’s canopy
  3. Direct your plant’s branches through individual holes in the screen
  4. Secure the branches with gardening ties 

While this may take some effort to execute, the results will more than make up for it. 

4. Move the Plant to the Edges

In some cases, training may not be the best approach. In this case, you can simply move your plants to the edge of the light’s throw. The light is strongest in the center and weaker on the sides, so this will prevent light burn and rein in your plant’s growth. Just don’t do this if your plant is already stretching due to lack of light — this can make it stretch even more as it tries to get closer to the light source.

How to Control Your Plant’s Height During the Flowering Stage?

How to Control Your Plant’s Height During the Flowering Stage?

As mentioned above, most often, you will identify and fix the problem of your plant growing too tall during the vegetative stage, but life sometimes happens, and you may not be able to fix the problem on time. However, not all is lost. You can still fix your plant during the flowering stage with the following tips. 

1. Increase the Height of the Grow Lights

The first thing you can do if your plant has grown too tall since your options are limited is to raise the height of the grow lights. Your plant will not stretch during the entire flowering stage, so your priority is to prevent light burns on your plant and get the best out of your plant. So, move the lights so the right distance is maintained between the light source and the canopy.

2. Reduce Daylight Hours Per Day

Your cannabis plant uses light to grow, so by reducing the number of light hours, you can stop it from growing too tall. As an additional benefit, doing so will also reduce humidity and prevent mold on the buds — just make sure you only do it to control the flowering stretch, so you need to cut the light hours before your plant stretches. 

Alternatively, you can reduce your light’s intensity to create the same results. This method may reduce yield slightly, but it is preferable over growing a shabby bunch of buds due to improper lighting conditions. 

3. Try Progressive Harvesting 

When your cannabis plant gets too tall and is at risk of light burn, you should consider harvesting the buds at the top as soon as possible. Once the trichome on the upper buds turns milky, harvest them. Doing this will increase the light the lower colas get, and you can harvest them as soon as they are ready. 

4. Supercrop Your Plant

If nothing seems to work, your last resort should be to super crop your cannabis plant that’s growing too tall. This is a high-stress method that will damage your plant, forcing it to focus its energy on recovering instead of growing. So, only use this as a damage control method to save what’s left of your yield. Try to do this as soon as possible so at least the lower branches get to grow and develop more buds. 

How to Prevent Your Cannabis Plant from Growing Too Tall?

How to Prevent Your Cannabis Plant from Growing Too Tall?

Your plant growing too tall can be a problem, but it is not the end of the world. Think of it as a learning experience — learn from your mistakes — and you will prevent this problem from occurring again. But that’s not enough; here are some more tips to help you prevent this problem in your next batch of cannabis. 

1. Use the Right Sized Pots

Pot size is partly responsible for how big your plant gets; the bigger the pot, the bigger the plant since there is more room for the roots to develop. So, avoid using pots that are too big and only use containers that are appropriate for your plant’s size. 

Large containers also pose another problem — the roots may not get enough nutrients, leading to symptoms of nutrient deficiency in your plants. 

2. Place Your Grow Lights at the Right Distance

You should invest in a set of high-quality grow lights and follow the manufacturer’s recommendations to set their height. Also, always focus on the PPFD your plant needs and ensure your light produces enough light in the right spectrum and distance to prevent your plant from growing too tall. 

3. Always Purchase Seeds from Reputable Dealers

It is always a good idea to purchase seeds from reputable dealers as they are transparent about how the plant will grow, including the rough height you can expect it to reach during its life cycle. Such seed banks also offer high-quality seeds with stabilized genetics, so you don’t have to worry about anomalies. 

4. Switch to Flowering at the Right Time 

Don’t let your cannabis plant stay in the vegetative stage for too long. Remember, cannabis plants experience a flowering stretch during early bloom, so you must account for that when considering your plant’s height. 

If you expect your plant to grow a certain height, it shouldn’t grow to that height in the vegetative stage. Always leave room for the flowering stretch. Depending on the strain you grow, it can be as much as twice the size of the plant in the vegetative stage. 

Summary: What to Do If Your Cannabis Plant Grows Too Tall?

Cannabis can grow tall for several reasons — unknown phenotype, excessively long vegetative stage, wrong grow light height or intensity, etc. But it is only a problem if the plant is stretching in search of more light. So, the best solution is to fix your lighting system by adjusting it or completely replacing it with appropriate grow lights. 

On the other hand, you also need to take some more precautions. For example, you must train your plant to control its height in the vegetative stage. During the flowering stage, you can increase the height of your grow lights and accept the fate of your plant, reduce daylight hours, or try progressive harvesting. 

Lastly, you need to keep a few things in mind, like using the right-sized containers, following the manufacturer’s recommendations when setting grow light height and purchasing seeds from reputable seed banks. Also, don’t forget to account for the flowering stretch!