How to Grow Tall Autoflowering Cannabis Plants?

Let’s first address the elephant in the room — autos are known for their small, discreet stature. So, why would you want them to grow tall? There can be many reasons. 

Some growers are not looking for discreet plants, but they pick autos for another benefit — they’re easy to grow. This ease of growth shouldn’t come at the cost of yield, and the taller the plant, the better the yield. 

So, if you want to grow an easy cannabis plant in a short time without fiddling around with lighting schedules, autos are the way to go. And you can use various techniques to grow tall autoflowering cannabis plants. 

In this article, you’ll learn about the average height of autos, the factors that influence that height, and what you can do to make them grow even taller. 

Understanding Autoflowering Plants

Autoflowering plants are just as popular as photoperiod cannabis plants. When you grow photoperiods, they flower according to the light they get. This means that while the plants are going to grow well with 18/6 hours of light in the vegetative stage, you'll need to shift to 12 hours of light and 12 hours of darkness to trigger flowering. 

However, you don't need to do any such thing with autoflowers as they switch to flowering automatically. They start flowering based on their age rather than changes in light exposure. This feature originates from the Cannabis Ruderalis subspecies that adapted to extreme climates and brief growing seasons. Unlike photoperiod cannabis varieties, autoflowers start blooming after a specific duration, typically within 4-6 weeks of sprouting regardless of their light intake.

There are many advantages of growing autoflowers that make them perfect for both beginners and experienced cultivators. Some of them are:

1. Compared to photoperiod plants, autoflowers have a quicker life cycle, usually reaching maturity in 8-12 weeks from planting to harvest. This rapid development allows you to harvest the buds multiple times, thanks to their short growing seasons. This is especially advantageous for outdoor growers in regions with shorter growing seasons. 

So, if you harvest during the spring, summer, and fall, you have harvested three rounds of autoflowering plants annually, which means that the total yield will be notably higher compared to a harvest of photoperiod plants.

Even indoors, autoflowers give you the joy of witnessing the fruits of your labor in just a few weeks. This rapid progress is particularly enticing for beginners.

2. These plants are generally smaller and more compact, making them perfect for growers with limited space. Nevertheless, you can purchase strains that grow taller and stronger and produce better yields. 

3. Autoflowers are tough and resilient and thrive in many types of climates. As low-maintenance plants, they will grow well as long as you provide the basic requirements. Thanks to their nature of flowering automatically, they are simple to cultivate and you don't have to plan the schedules extensively like you would with photoperiods. 

4. Their small size and quick growth make them perfect for discreet cultivation. This is especially beneficial for individuals who prefer to keep their growing activities under the radar.

5. Autoflowers also allow you to harvest perpetually. So, if you have a few autoflowers or even photoperiods in your growing tent, you can sow seeds and have them ready to transplant just as you harvest a fresh batch. This way, you can have a steady batch of plants, naturally offering more yields than ever. 

6. A shorter lifespan reduces vulnerability to pests, diseases, and unfavorable weather conditions. The limited time frame minimizes the likelihood of facing challenges that could impact plant health and yield.

7. Autoflowering plants efficiently utilize resources like light, water, and nutrients. Their quick growth cycle ensures these resources are put to good use, cutting down on waste and reducing cultivation expenses.

How Tall Do Autoflowers Grow?

Autoflowering cannabis strains are famous for being compact and discreet, which makes them popular among many growers. These plants stay relatively stout throughout their life cycle and grow much faster. 

But how tall do they actually get? Well, their height is influenced by various factors like container size, genetics, location, temperature, light, etc. We’ll get more into this later. However, depending on these conditions, your autos can either grow really short or kinda tall. 

Most of them will not be as tall as photoperiod plants, but with the modern ones, you never know. Not only are they at par with photoperiods when it comes to potency, but they are also good with yields. 

Usually, autoflowers strains grow around 40 to 160 cm. During the early stages of their growth, they grow about 5 to 10 cm and develop sets of true leaves before vegging. They grow another 5 cm every day during this stage. 

• Indoor Autoflowering Height 

When you’re growing autos indoors, it often means you’re working with limited space. In small pots, the roots don’t have a lot of room, which can limit the plant’s growth and height. Still, in modest-sized containers, your autos can reach their maximum potential. 

Generally, you can expect them to grow from 40 to 100 cm indoors. 

• Outdoor Autoflowering Height 

On the other hand, outdoor plants have more soil and space, and natural sunlight also comes in quite handy. This makes outdoor autos grow larger and taller, even if you’re growing them in raised beds or containers. 

So, you can expect your outdoor autos to grow around 100 to 140 cm, and some of them can even reach up to 150 cm. 

Significance of Plant Height

The height of autoflowering plants greatly influences their development and productivity. While these plants typically have a small stature, cultivating autoflowers can offer various benefits, including:

• Enhanced Light Exposure: Taller plants facilitate better penetration of light through the foliage ensuring that more leaves and buds receive ample light. This could result in better growth and enhanced photosynthesis leading to increased plant health and productivity.
• Increased Yields: Taller autoflowering plants tend to yield more compared to smaller ones. The added height provides more space for bud sites to develop, resulting in a better harvest.
• Use of Space: Indoor growers may find maximizing space more efficient than spreading plants horizontally. Taller plants can utilize grow tents or vertical growing areas effectively, allowing for more plants within the same footprint.
• Enhanced Plant Health: Taller plants usually have sturdier stems and branches that offer support for heavy buds. No, not the leggy ones that become weak due to being placed far away from the grow light. However, the ones that grow tall with proper nutrients and care have a structural strength that prevents branches from breaking due to excess flower weight, ensuring the plants’ well-being throughout their growth cycle.
• Bud Quality: Taller plants often yield higher-quality buds as they receive more light and air circulation. This can lead to denser flowers with enhanced flavor and aroma profiles. Of course, this is applicable only if you take the necessary steps to provide airflow. Since the plants are going to get tall, they will need lots of airflow. Good airflow can not only prevent mold, mildew, and other diseases, but it also prevents hot spots where there's too much light in specific regions. It also aids in reducing moisture through evaporation lowering the risk of root rot.

In essence, although autoflowering plants are typically favored for their size and quick growth cycles, there are some benefits to growing taller variations. However, the responsibility of providing proper light and airflow falls on your shoulders. 

How to Make Your Autoflowering Cannabis Grow Taller?

Now that you know some of the important factors behind your plant’s height, let’s take a look at some tips to help your autoflowering cannabis plant grow taller. 

1. Pick the Right Container 

Let’s start by picking the right container for your autoflowering cannabis plant. This step is crucial if you want to make your plant grow as tall as it can. The bigger the root system, the bigger the canopy, and vice versa. Many growers prefer using 11-liter pots for manageable and healthy plants. However, if you aim to maximize your plants' height, consider using 20-liter containers or larger.

Also, compared to smaller pots, larger pots provide better stability so the plants won’t tip over and fall even if they are burdened with loads of buds. You can even secure the branches to the sides to prevent mishaps. 

But, since you want the roots to develop as much as possible, the type of container you choose will matter as well. There are many types of containers and you can choose any of them. However, the most popular ones are fabric pots, air-pots, and plastic pots. 

Fabric pots are the most popular of them all as they offer many advantages. They are crafted from materials that enable air to permeate the soil from all directions. This encourages air pruning, a process where roots are exposed to air and gradually wither at the tips, prompting the plant to develop lateral roots. The enhanced oxygenation and drainage also help avoid overwatering and root rot, making them a perfect choice. 

In short, the air pruning process fosters a denser root system. This boosts the plant’s capacity to absorb nutrients and water, helping it grow beyond your expectations. Unlike other pots, fabric pots allow roots to naturally expand, preventing the conditions that can cause root binding.

You can also use plastic pots but a major disadvantage is that the roots often encounter the edges and start forming circles, leading to a twisted and ineffective root structure. Fabric pots prevent this by encouraging root growth and air pruning.

The breathable design of fabric pots ensures that roots receive an abundant oxygen supply. Oxygen is vital for root respiration, which is essential for water and nutrient absorption.

Another advantage of using fabric pots is that they promote drainage, preventing water buildup at the bottom of the pot. This helps avoid overwatering issues that can cause root rot and other water-related problems.

They also regulate soil temperature by allowing excess heat to escape, which is especially beneficial in hot climates or summer months to prevent root issues. Most importantly, they are portable and are available in many sizes so you can choose anything depending on your plant’s requirements, whether they are compact or tall. But, since you’re trying to grow taller plants, choosing larger ones is a better idea. 

If you don’t have access to fabric pots, you can use plastic pots as well since they are easily accessible, sturdy, and often more budget-friendly compared to other options. But, you must poke drainage holes at the bottom if they don’t have them to let the water drain away.

Air-pots are similar to fabric pots as they feature a design with perforated sides that stimulate air pruning of roots. This encourages the root system to grow freely and improves overall plant health. If you’re planning to grow tall autoflowers, air-pots are especially beneficial as they can easily hold the weight. 

No matter what container you choose, make sure there’s proper drainage to avoid water pooling at the bottom of the pot as this can result in root rot and various other problems. Make sure the container you pick has plenty of drainage holes or add perlite or gravel at the bottom for drainage. 

Plastic pots don’t allow this, but if you can, pick a container that allows aeration since the roots can breathe easily. 

If you’re growing outdoors, go for larger containers (20 liters or more) as they support extensive root systems and help plants grow taller. On the other hand, if you’re growing outdoors, think about the space you have. While bigger containers encourage growth, they need to fit within your setup. You should use containers that you can move easily if you decide to rearrange the plants.

2. Genetics 

Genetics plays a major role, too. Sativa-dominant strains generally grow taller, while Indica-dominant strains tend to be shorter and bushier. For example, Haze family autos can reach 100 to 120 cm before blooming and stretch further 40 to 60 cm during the flowering stretch. So, pick autoflowering strains that are known to grow taller (around 150 cm). The height listed on the product will be average height, and you can always push it a bit further. But you can’t make a short auto grow taller than it is capable of. 

As you can understand, selecting the strain is key for cultivating autoflowering plants successfully. Different strains come with different growth patterns, heights, and needs. By focusing on strains renowned for their height, you can increase your chances of growing tall autoflowers. 

Some autoflowering strains are specifically bred to grow really tall. Here are a few strains known for their height;

Amnesia Haze Auto: Amnesia Haze Auto can grow up to an impressive height of about 1.2 meters. This strain is a sativa hybrid known for its wonderful effects and relatively short flowering period.

Sour Diesel Auto: Another Sativa strain that tends to grow tall often reaching heights of 1.2 to 1.4 meters is Sour Diesel Auto. It is valued for its generous yields.

Super Lemon Haze Auto: Celebrated for its towering height and bountiful harvests, Super Lemon Haze Auto can reach heights of up to 1.2 meters. It produces resin-filled buds with a zesty citrus scent.

Jack Herer Auto: Jack Herer Auto is yet another example of an autoflowering strain that can grow as tall as 1.2 meters in height and offers a mix of Sativa and Indica qualities.

Still, what type of plants should you choose? What if the plant you like is not in the list above? Well, you can look at a few factors when purchasing seeds:

• Genetic Factors

When deciding on a strain based on height preferences, understanding the lineage is crucial. As you already know, Sativas are generally taller with more distance between the internodes, making them ideal for those aiming for taller plants.

Their natural inclination to reach towards the sky makes them perfect for growers with lots of vertical room. However, remember that sometimes, although sativa-dominant autoflowers will still bloom automatically, they may have a longer flowering phase compared to indica-dominant autoflowers.

On the other hand, Indicas typically have shorter and denser growth patterns. They grow in a bushy manner, making them suitable for growers with limited horizontal space. However, this feature may not be ideal for those looking to grow tall autoflowers. They also have a shorter flowering phase compared to Sativas, allowing you to harvest more but they don't grow as tall as Sativas.

You can also go for hybrid varieties that are a blend of both Sativa and Indica genetics, creating a mix of characteristics from each type. These hybrids can be customized to showcase traits like the towering stature inherited from Sativa strains and the abundant bud production typical of Indicas. Thus, if you're purchasing a hybrid, make sure it leans more toward sativas. This way, they may display the height of Sativas while potentially retaining some qualities that boost yield and resin development.

• Choose a good breeder to buy seeds from

Breeders create strains with some specifications in mind. For instance, while some strains produce lots of resin, others may be bred for aroma, taste, etc. Similarly, you need to look for strains that are bred to grow tall. But, first, delving into a breeder's background and reputation can offer insights into a strain's potential. Make sure you buy only from trusted breeders as they test their strains several times which can often take years to ensure they perform as advertised. This increases your chances of getting seeds that will develop into tall plants.

3. Learn To Water Your Plant 

Picking the right container is one side of the story; the other is watering your plant properly. Since your autoflowering plant’s first container is the final one, it can be a bit too big for your plant’s stature. 

For example, you’d use multiple containers for a growing photoperiod plant, but you can’t do the same with an autoflowering plant. 

Here comes the problem — overwatering. Many growers overwater autos due to the larger containers, but this can lead to oversaturation of the growing medium. This can then affect the plant’s growth as it no longer has to grow looking for water. 

So, even if your container is a bit big for your growing autoflowering cannabis, avoid overwatering at all costs. You only need a little water; for example, around 300 ml is enough for a 20-liter container — every 2-3 days. Although, adjust this number based on your weather conditions. 

Start with this watering regime during the early stages of your plant’s growth; once the plant grows a bit tall, you can gradually increase the nutrients in it. Once the plant approaches bloom, you can then treat it as a regular plant. By this time, the container will no longer be “too big” for the plant. 

4. Lighting Conditions (Intensity and Color)

Apart from the factors mentioned above, the environmental conditions around the plant also matter, but lighting is the most important. 

Light is essential for plant growth as it aids in photosynthesis, enabling plants to build their cellulose structures. Adequate lighting not only boosts yields but also influences plant height. 

Plants deprived of light tend to grow tall and spindly as they stretch towards light sources. In contrast, if you grow your autos with ample light, they will remain compact, healthy, and strong. 

Growing tall autoflowering plants requires detailed attention to ensure that all parts of the plant receive light for healthy growth and optimal yields, especially during the flowering phase when buds develop along the plant's entire height.

Here are a few things you should keep in mind:

• Light intensity: It plays one of the most important roles in determining the plant’s height, after genetics. Therefore, it's important to use grow lights with high intensity, including HID lights like HPS and MH, and even high-quality LED lights to prevent lower branches from developing popcorn buds due to insufficient light. In addition, Utilize materials such as Mylar or white paint on the grow room or tent walls to enhance reflection and distribution throughout the growing area.
• Light penetration: Ensuring adequate light penetration is essential for plant health. Techniques like defoliation and Low Stress Training (LST) can improve penetration to the lower parts of taller plants promoting balanced growth and development. 
• Distance between lights and plants: As autoflowering plants grow taller, the distance between the source and the plant's top changes. So, you need to adjust the lights according to the plant’s growth to ensure that they don't get too leggy. Adhere to manufacturer guidelines for elevation usually ranging from 12-24 inches for LEDs and 18-36 inches for HIDs depending on intensity and plant growth stage.

Here's the thing: distance is really important, so don't ignore this. You're probably going to purchase a high-intensity light to make sure the plants get adequate light. But, if you place it too close to the plant, they will end up getting burnt and produce little to no yield as autoflowers don't have enough time to recover. If you place the grow lights far away, the plants get leggy and weak and produce low yields again. 

Ultimately, you'll be achieving the opposite of what you want, so pay close attention to how the plants react when you adjust the lights. This way, you will achieve uniform light distribution throughout the entire canopy avoiding hot spots. 

• Supplemental Lighting: You can use supplemental side lighting and position them around the sides of the growing area to ensure illumination for lower portions of the plants. They can be quite handy in growing spaces where overhead light might not reach the lower branches effectively. LED bars and strip lights are great choices for side lighting due to their adaptability and efficiency. This way, you'll avoid the chances of the plant developing popcorn buds to a great extent. 

You can also use under-canopy lighting and position lights beneath the plant canopy to brighten up certain sections of the plant. This method ensures that light reaches the underside of the plant, which can help the plant develop buds on the side branches. Typically low-intensity LED lights are used for this purpose.

5. Use the Right Nutrients 

To help your autoflowering cannabis plants grow tall, using the right nutrients is crucial. Start by choosing high-quality cannabis nutrients. And always follow the manufacturer’s recommendation on mixing the nutrients. 

Feed your plants “Vegetative” or “All-purpose” nutrients for the first 4-6 weeks to encourage height growth. Once your plants stop growing taller, switch to “Flowering” or “Bloom” nutrients to support bud development. 

Just don’t overfertilize your plant, as autoflowering strains are sensitive to high nutrient levels. If you’re unsure, be conservative with the nutrients at first and see how your plant reacts to it. Dilute the nutrients at any hint of nutrient toxicity. 

It’s also important to keep an eye on pH levels. For soil, maintain a pH of 6.0–7.0, and for coco, keep it at 5.5–6.5. To check the pH, compare the pH of the nutrient solution and the run-off water. Both the readings should be similar and within the recommended ballpark figure. You can use pH up/down solutions to change the pH of your nutrient solution.

6. Temperature and Humidity 

Finally, we come to the temperature and humidity, which also impact the height of your cannabis plant. High temperatures can lead to heat stress and low temps can cause stunted growth. 

Additionally, high humidity can lead to mold and other issues, and low humidity can lead to drying out. On the other hand, optimal humidity can benefit nutrient uptake and lead to a much better plan of growth. 

7. Don’t Forget to Train Your Autoflowering Cannabis

If the reason you’re growing tall autos is for the yield, you can also try training your cannabis plants. These techniques may not necessarily increase your plant’s height but they will certainly increase the yield. Here are some techniques you can use. 

Low-Stress Training 

One of the best methods for encouraging bud development without causing stress is Low-Stress Training (LST). With LST, you gently bend and tie down the branches to create a flatter, more even canopy. 

Yes, it kind of makes your plant shorter, but if the goal is to get bigger yields, this technique will get you there. 

Screen of Green 

With ScrOG, you place a screen or net above your plants and guide the branches through the gaps. This method ensures even light distribution, leading to much better bud development, thereby significantly increasing your auto cannabis’ yield. 

Pruning 

While pruning isn’t typically recommended for autoflowering strains due to their short life cycle, you can use minimal pruning to manipulate its height if necessary. Just be sure not to over-prune, as autoflowers have limited time to recover from any stress you cause. 

Speaking of recovery, avoid training your cannabis plant with high-stress methods. Your plant does not have enough time to recover, and doing so can lead to a shorter plant instead of a taller one. So, stick to low-stress methods and be very cautious. 

Summary: How to Grow Tall Autoflowering Cannabis Plants?

Growing tall autoflowering cannabis plants might seem like a challenge, but with the right techniques and knowledge, it’s entirely achievable. While autos are known for their compact and discreet nature, you can still push them to reach impressive heights and increase your yields.

By choosing larger containers, selecting tall-growing strains, and providing optimal lighting, you set the foundation for your plants to grow taller. 

Training methods like Low-Stress Training and ScrOG can help you manage height and maximize yields, while careful nutrient management and pH monitoring ensure robust growth throughout the plant’s lifecycle.

So, embrace these strategies and get ready to see your autoflowers stretch to new heights. With a bit of effort and the right approach, you can turn those small, easy-to-grow plants into towering giants that produce a bountiful harvest.