13 Tips to Grow Big, Massive Autoflowering Cannabis Plants

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Added 10 June 2022

Autoflowering cannabis plants have a bad reputation for their size — many growers still think that they tend to grow small and return low yields. While this statement was largely true since autos are genetically designed to grow smaller in stature than photoperiod plants, some modern autoflowers grow as big as photoperiod plants. With the right strain, you can maximize your yield by growing big autoflowering plants.

Growers choose autoflowering plants for various reasons, such as the following:

  • Autoflowering plants are easier to grow and don’t require a lot of experience and equipment.
  • Since they are smaller in stature, you can grow them discreetly in your backyard. 
  • They are resilient plants and can grow in various climatic conditions.
  • Thanks to their short life cycle, you can enjoy multiple harvests each season.
  • Again, their short life span keeps them relatively safe from mold and pests since they are less exposed to bad conditions. 
  • They are perfect for guerilla growth since they don’t require a lot of care or training and mature within a couple of months.

You may be growing autoflowering cannabis for any of these reasons, but what if you don’t want to compromise on yield? Well, that's what this article aims to achieve. In this article, we list various techniques and tips that can help you grow big autoflowering plants.

Common Autoflowering Problems and How to Fix Them

autoflowering cannabis

Autoflowering plants grow short for one major reason — genetics — they are designed to grow small, fast, and reach maturity within a couple of months. So, on average, an autoflowering plant will only grow up to a meter, whereas its photoperiod cousin can reach up to three meters!

However, apart from genetics, various other factors also influence the plant’s growth, size, and yield. Below are these factors and how to fine-tune them to grow big autoflowering plants.

1. Understand the Autoflowering Season

autoflower grown outdoors

Image credit - Shinsimilla

Like photoperiod cannabis, autoflowering plants also enjoy heat and sun. So, depending on where you live, you may either have several harvests (long summers) or just one harvest (short summers). Everything depends on your local climate. 

For instance, in Mediterranean Europe, you can start growing autos in mid-April without the risk of frost. And you can harvest these plants by the end of July and sow more plants in August, which can be harvested again in October. 

And in Northern Europe, you can safely grow your plant in June, when the days are warm. Such weather would ensure your plant grows vigorously during the long daylight hours and enter its flowering stage during peak summer. And you can harvest these plants before the winter sets in, unlike photoperiod plants that mature as late as September. 

So, figure out your local climate and discuss with other growers to know the best autoflowering season for you. Your best bet is to get in touch with local growers in your area. 

2. Learn All You Can About Growing Cannabis

autoflowering marijuana

Understanding the autoflowering season is just one part of the puzzle, but a lot more goes into growing big autoflowering plants. Before you even begin germinating your seeds, you need to plan your cultivation and learn everything about it.

For planning, you must gather as much knowledge as you can about your local climate, common practices, best strains, nutrients, watering cycle, and much more. Now is the time to prepare yourself for the growing season. 

You can stay tuned to our blog to know all about growing high-yielding cannabis plants using the best techniques. Also, you can participate in various cannabis grower forums or read the array of literature available on the internet.

3. Harness the Right Genetics


Image credit - EL-TUCO

Whether you are growing a photoperiod plant or an autoflowering one, you must start by choosing the right strains. The strain is not only responsible for the weed’s flavor, aroma, and effects, but also for how the plant grows. 

Here, you must aim for quality. AlwaImage credit - EL-TUCOys choose premium seeds from reputable seed banks as they offer better germination rates. And narrow down the characteristics you want to aim for — spicy flowers, high-CBD content, or long-lasting body high — whatever suits you. 

Once you have selected a reputable source and its characteristics, you can then choose the strain to order. Avoid strains that inherently grow small. Instead, check out strains that grow big, like Gorilla, Mimosa, White Widow, Northern Light, or HulkBerry Auto. 

If the genetics of the strain support big size, you are already getting a head start in the race to grow bigger plants. Look for "XXL" specified by breeders in their catalog to get more info on the size. 

4. Use the Right Germination Techniques


Image credit - EasyName

Germination problems are another aspect of the plant’s growth that may hamper its size. If the start itself is not good, the plant will not grow as vigorously. So, you must ensure your plants get the ideal start for healthy growth. 

Autoflowering plants use an internal genetic clock to grow and flower, which starts ticking the moment the seeds sprout. An ideal germination process will ensure that the seed germinates and sprouts as quickly as possible, so the plant gets to enjoy more light and generate more energy. 

Many growers prefer the simple paper towel method to germinate autoflowering seeds as it has a high success rate and avoids issues related to soil-germination, like damping off. 

To use this method, dampen a paper towel and place your seeds over it at an even distance. Then, place another damp paper towel over them, and place it in a dark place. Once the seeds have developed white roots (of around 2 to 3 cm), carefully transfer them into the final growing container.

5. Choose an Airy Growing Medium

growing medium

Autoflowering plants tend to grow better in a growing medium that is not too dense and has more air pockets. An airy medium helps the plant’s roots grow throughout the substrate easily, especially during the early stages of its growth. 

On the other hand, thick or dense grow mediums can inhibit roots’ growth, which can slow down the plant’s growth. You can choose from various growing mediums, like soil, coco coir, perlite, etc. Figure out the one that fits your preferences and growing setup, and choose that. Autoflowering plants fare well in most mediums.

6. Choose the Right Containers

right size containers

Next comes containers, which also play a major role in the plant’s development. The size of the container dictates how big (or small) the plant will grow, and its type can also play a major role in the same. Here is more on the size and type of containers you must use.

Pot Size

Many growers make the mistake of growing autoflowering cannabis in smaller pots. You can choose smaller pots if you intend to keep the plant small and discreet. But if you want to grow big autoflowering plants, you must choose larger containers. 

The roots grow quickly and fill out their container, and if they run out of room, the plant will stop growing in size. However, don't use pots that are too big as they affect the plants adversely. In addition, big pots will hold too much water and you'll struggle with overwatering issues. 

For a big autoflowering plant, the ideal size of the container must be at least 11 liters as the roots can grow adequately within it. You can also go up to 4 gallons as long as you water them properly

Pot Type

On the other hand, the type of container you choose can also influence the roots’ growth and health. 

The by-default option for most growers is to use plastic containers, but they lack adequate aeration and are prone to waterlogging, which can hamper the roots’ growth. Instead, you can choose modern containers like fabric or smart pots.

Fabric or smart pots allow more air to circulate within the substrate while also offering better drainage. So, not only will the roots grow properly but also be less prone to disease or rot. 

Lastly, avoid transplanting autoflowering plants. Autos work on a genetic clock, so they cannot afford to lose time where the plant settles into a new pot. Once the seeds germinate, transplant them directly into the final container. 

7. Let There Be [Enough] Light

autoflowers in greenhouse

Plants generate energy thanks to photosynthesis, and the more light they get, the better they will grow. So, you need to ensure your plant has adequate light always, and here's how you do that:

Light for Indoor Autoflowering Plants

If you are growing your plant indoors, you need to add supplementary lights for the plant. Of course, many growers simply place their autoflowering plant on the windowsill, but the natural light won’t be enough to fuel the plant’s growth. 

Instead, you can use cannabis-specific growing lights that produce at least 400W of light for a big autoflowering plant. Here, we recommend using LED or ceramic lights. 

HPS lights work well enough for a big plant, but they produce a lot of heat that can cause heat stress and consume a lot of energy. On the other hand, ceramic light of 325W produces the same light as an HPS light of 600W. 

LED lights are the most popular lights among growers because it offers high performance and better energy efficiency. Also, LED lights can be tuned for the blue-dominant spectrum for the initial weeks of the growth and the red-dominant spectrum for the flowering stage, which can lead to better growth and higher THC levels, respectively. 

You must also narrow down your light cycle. Autoflowering plants can handle light cycles of even 24 hours, but that is overkill. For the best results, stick to a light cycle of 18 hours and a dark cycle of 6 hours throughout the growth cycle. 

Lights for Outdoor Autoflowering Plants

If you are growing an outdoor autoflowering plant, you won’t have much control over the light cycle. Fortunately, autoflowering plants are resilient and can handle shorter growing seasons with fewer daylight hours, unlike photoperiod plants that grow best in warm, sunny regions.

Still, there are a few things you can do to maximize the light your outdoor plant gets. Since autos mature within 8 to 10 weeks, you should aim to germinate your seeds in May or June, so your plant gets to bask in long daylight hours. 

And when you transplant your seedling into the container, you must place them in a south-facing location, which gets the maximum amount of sunlight during the day. 

8. Correct the Watering Cycle

autoflowers watering cycle

The watering cycle is essential for a plant’s growth, and an incorrect watering cycle can do more damage than good to your plant. It can even derail your plant’s growth and compromise the yield.

Cannabis plants require a lot of watering during each growth stage for various purposes, like photosynthesis, turgidity, or nutrient transport. Due to this, many new growers tend to overwater their plants, which is not good for the plant.

If you overwater your plant, the water may pool in the substrate and drown the roots. Overwatering can also encourage the growth of anaerobic bacteria, which cause root rot or lead to nutrient deficiencies. 

For the best results, you should water the growing medium to its 25% to 33% capacity. But this can be hard to judge by simply looking. So, just water your plant enough that it can hold water without too much of it draining out. And wait for the upper inches of the soil to be completely dry before watering again.

9. Dial in the Temperature and Relative Humidity

temperature to grow autoflowers

Next, you need to dial in the environment for your plant, specifically the temperature and humidity. This is because cannabis plants grow best in specific temperature and humidity ranges. 

Of course, these aspects may be difficult to control outdoors, but for indoor plants, you can use various devices like fans, humidifiers, dehumidifiers, or heaters to dial in the temperature and humidity.

The ideal temperature for an indoor autoflowering plant must be:

  • Seedling stage: 20°C to 28°C (68°F to 82°F)
  • Vegetative stage: 20°C to 28°C or even 30°C if there's enough airflow and correct humidity (68°F to 82°F)
  • Early flowering stage: 18°C to 26°C (64°F to 79°F)
  • Late flowering stage: 18°C to 24°C (64°F to 75°F)

And the relative humidity should be around:

  • Seedling stage: 60% to 70% RH
  • Vegetative stage: 40% to 70% RH
  • Early flowering stage: 40% to 50% RH
  • Late flowering stage: 30% to 40% RH

Additionally, you can also add more carbon dioxide to your grow room to increase your yield. This is because cannabis plants can use the extra CO2 to produce more energy and grow bigger. However, this is an advanced growing technique, so proceed only if you have enough experience. 

10. Mix the Right Nutrients

nutrients for autoflowers

Apart from water and light, the next thing your plant needs to grow well is nutrients. Cannabis relies on various macronutrients (nitrogen, potassium, and phosphorus) and micronutrients (boron, calcium, magnesium, etc.) to carry out its various physiological functions.

For instance, nitrogen is required for developing green leaves, potassium boosts flowering, and calcium encourages better root health.

However, autoflowering plants require fewer nutrients than their photoperiod cousins. So, you must choose a high-quality potting mix that is already rich in various nutrients. Apart from that, you can also apply worm casting or compost on the medium that will leach nutrients over time. 

If you want to ensure your plant gets all the nutrients, you can purchase nutrients from your nearest horticultural store. However, only apply 50% to 75% of the recommended dosage since autos require fewer nutrients. 

When nutrients are not fed in the right quantities, your plant may suffer nutrient deficiencies. So, learn how to identify these problems. For this, look at the leaves as they are the window to a plant’s health. 

so proceed only if you have enough experience. 

11. Always Maintain a Balanced pH

pH for autoflowering cannabis

pH is a hidden aspect that dictates how your plant grows. Essentially, pH is the number of hydrogen ions within a solution, and it ranges from 0 to 14.0. If the pH is below 6.0, the solution is acidic, and if it is over 8.0, it is alkaline. 7.0 is neutral pH.

You must maintain the pH of the growing medium for better plant growth. The cannabis plant grows best at a slightly acidic pH. If the pH is too far off, it can lead to various problems within the plant that may hamper its growth and yield. pH is crucial because the roots fail to absorb all the nutrients with an improper pH. This can lead to nutrient imbalance, deficiencies, or lockout within the plant. 

For a soil-based autoflowering plant, the ideal pH range is 6.0 to 7.0, and for a hydroponic plant, the ideal range is 5.5 to 6.5. 

You should consider investing in a pH meter to measure the substrate and nutrient solution’s pH balance. And if the readings are off, you can use pH balancing products to rebalance them to the correct pH. 

12. Train Your Plant Well

training autoflowers

Training your plant is a process wherein you help the plant reach its full potential by tweaking its physical structure. This can range from cutting off some shoots or tying the branches off. However, we don’t recommend high-stress training for autoflowering plants.

Autoflowering plants are resilient and can easily handle low-stress training without requiring too much recovery time. So, simply start tying off the branches using a zip tie or a rope to open up and even out the canopy.

Low-stress training like this allows more air and light to penetrate the canopy and reach the buds on the lower tiers of the plant. This can significantly increase your yield. 

Or Try Screen of Green

If you don’t want to spend time typing the branches of the plant or you are worried your plant may not handle the training, you can choose the sea of green (SOG) method. This is an extremely popular method in autoflowering growing circles because it can help you get immense yields, although it kind of defeats the purpose of growing big auto flowering plants.

Here, instead of growing one big plant, you have to grow several small plants. This takes your focus away from maximizing the plant’s stature, so, you can take advantage of the smaller size of autoflowering plants. 

13. Know When to Harvest

harvesting autoflowers

Lastly, you must learn the right time to harvest. You have come this far and grown a big autoflowering plant, but if you mess up during harvest, it can drain all your efforts. 

The first step to harvest is to look at the trichomes on the buds. Use a magnifying glass to look at the flowers during the late flowering stage. If 50% to 70% of the pistils appear amber in color, the buds are ready for harvest. 

Do not wait too much once the trichomes turn amber as it can lead to a couch-lock effect when you consume the buds. And if you harvest too early, the flowers may be small and produce an unpleasant high.

You can even try progressive harvesting. The main colas of the plant, which are located at the top, tend to mature faster than those on the lower tiers. So, once the buds on the top tiers are ready, you can harvest them. And then, wait for a week before harvesting the buds on the lower tiers, which will give them enough time to grow big.

Summary: 13 Tips to Grow Big, Massive Autoflowering Cannabis Plants

That’s it — tips on growing big autoflowering plants easily. Use these techniques to grow big autoflowering cannabis and bust the myth that autos can only grow small. And you don’t need to overcomplicate everything. Just learn to read your plant and give it what it needs and it will grow well.

To summarize everything:

  • Choose the right strain that promises a bigger size
  • Give your plant the right environment, airy growing medium, and big-enough container
  • Choose an 18/6 light cycle supported by >400W LED or CMH lights 
  • Avoid overwatering the plant 
  • Keep an eye out for nutrient-related problems 
  • Regularly measure the pH and rebalance accordingly 
  • Train your plant well 
  • And know when to harvest your plant

There are many advanced growing techniques too like nutrient film technique (NFT) or deep water culture (DWC), but these are complicated and not recommended for small grows or novice growers. Until then, focus on deepening your understanding of growing cannabis. 

Lastly, show your plant lots of love and care. Plants grow well when they are well taken care of. 


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Bonjour, vous dites dans l'article que les autofloraisons mûrissent en 8 à 10 mois , ne serait-ce pas 8 à 10 semaines ?
@Dgessy, corrected it. Thanks for pointing it out!
Sinon vos articles sont toujours très intéressant , continué comme ça 😊
Cheers, really helpful for a newbie like me.