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Optimal Growing Conditions: Exploring Ideal Environmental Factors for Cultivating Autoflowering Cannabis

Added 18 August 2023

Cultivating autoflowers is a very simple process if you have a thorough understanding of the optimal environmental conditions needed for the plants to thrive. Unlike photoperiod strains, autoflowers transition automatically from the vegetative phase to the blooming phase based on their age instead of adjustments in light cycles. This distinct quality makes them very preferable for cultivators looking for a faster harvest and a convenient experience.

Autoflowers are popular for their resilience. Bred specifically to flourish in various climates, they are typically much more flexible in contrast to their photoperiod counterparts. This flexibility combined with appropriate growing conditions, makes autoflowers an outstanding option for both beginners and seasoned cultivators.

Many growers assume that autoflowers don’t yield as much as photoperiods. While this is partly true because of their small stature, autoflowers can yield as much if not more than photoperiods if you give them the right conditions. Also, since they flower faster, enabling you to harvest at the same pace, you can expect to grow more and get more yields in the same period. Incredibly, most autoflowers finish their lifecycle in a matter of 8-10 weeks as long as you take care of them well. 

By focusing on aspects such as temperature, humidity, pH, nutrients, ventilation, and more, you can provide an ideal environment to promote healthy growth. 

In this article, we will explore the optimum growing conditions necessary for cultivating some mind-blowing autoflowering cannabis. 

Ideal environmental conditions for autoflowering cannabis

1. Temperature 


Temperature level plays a critical role in cultivating cannabis successfully. This is because cannabis prefers different temperatures in its various stages of growth. By manipulating the temperature according to the plant’s growth, you can ensure that it grows well and produces excellent yields. 

When the plants are still in the seedling stage, they prefer temps ranging from 68°F to 77°F (20°C to 25°C). Then, throughout the vegetative phase, autoflowers love temperatures ranging between 70°F to 85°F (21°C to 29°C), as it provides the heat they require to produce lush leaves and strong stems. The higher range (29°C) promotes faster metabolism and nutrient uptake along with a robust root system; however, do not exceed these temperatures as the plants can get stressed and dehydrated. 

Remember, you must maintain a steady temperature level throughout the growing phase as any sudden changes can interfere with the plant's development, possibly leading to stunted growth. If it’s too hot or cold, use air conditioners or coolers and heaters accordingly.

Next, as your autoflowering plants change into the blooming phase, it’s best to reduce the temps slightly to around 65°F to 80°F (18°C to 27°C). Lower temperatures in this range throughout the blooming phase will help the plants produce maximum resin and terpenes as well. This way, you get to smoke tasty cannabis buds. 

In addition, decreasing the temps during the flowering phase can help you avoid heat stress that can adversely influence bud development and quality. Again, remember to maintain consistent temps throughout the blooming phase. Sudden changes can interfere with the plant's hormonal balance and also lead to hermaphrodites.

Apart from using heaters and coolers, you can use various strategies to take care of the temperature levels. If you’re growing indoors, for example, you can use HID lights if the temps are too cold. Alternatively, if your grow room is very hot, you can use LEDs. Adjusting the position of the grow lights will also help to reduce the temps. 

If growing outdoors, choosing the right time to plant your autoflowers in such a way that it aligns with the temperatures needed will help the plants grow well. For this, try and understand your climate well so you’re not stuck with odd timings. 

Lastly, remember that while some autoflower like slightly hot temperatures, others may prefer cold temps. Therefore, it’s best to read the specifics of a strain before purchasing it so you know how to deal with it. 

If you’re growing autoflowers using hydroponics, you must take care of the water temperature as well. Typically, water temperatures around 65 to 68°F (18°C to 20°C) will be appropriate for cannabis plants. Make sure the temps don’t get too hot or you’ll create the perfect environment for various water-borne infections that usually arise when there’s a lack of oxygen. 

2. Humidity


Humidity is a vital aspect to think about when growing autoflowering marijuana plants. Proper humidity levels play a crucial duty in plant transpiration, nutrient uptake, and general growth. 

Again, cannabis plants like to have different levels of humidity according to their growing phase. During the seedling phase, autoflowers will love humidity levels varying from 65% to 70%. Since the root system isn’t yet established at that stage, high levels of humidity will help the plant intake water and nutrients. 

Once the plants transition to the vegetative phase, they prefer slightly lower levels ranging from 40 to 70%. Do not reduce the humidity levels instantly; instead, decrease them by about 5% every week as it helps the plants adjust easily. This level of humidity will provide the moisture needed for the roots to intake nutrients and water efficiently. 

In addition, proper levels of humidity will prevent excessive transpiration, minimizing the danger of dehydration and nutrient shortages. Slightly higher levels of humidity in the vegetative phase will create a positive environment as the plants will be able to produce a lot of leaves and grow an extensive root system as well. 

However, do not go overboard with humidity. You have to strike a balance, as extremely high humidity levels will encourage mold and other fungal issues. Plus, they can invite all sorts of pests including spider mites. You should also maintain proper ventilation (we will discuss this later in the article) during this phase. 

As autoflowering plants change into the blooming phase, it’s best to slowly reduce humidity levels to around 40% to 50%. Decreasing the moisture throughout blooming gradually will prevent the possibility of bud rot and various other moisture-related problems that can affect bud quality. 

Low humidity levels during the flowering phase will encourage the buds to produce lots of resin, so you can employ various methods to keep the humidity in check. First off, get a hygrometer to gauge the levels. If humidity levels are above the recommended range, use dehumidifiers to remove excess moisture. 

Conversely, if you live in a dry environment with low levels of humidity, use humidifiers or place water trays in your grow room to elevate humidity. Make sure you monitor the levels frequently to avoid issues. 

You can manipulate the temperature and humidity easily indoors, but it’s not the same outdoors as you have little control. Thus, you don’t have much choice apart from choosing locations that don’t have extremely high or low humidity levels. In addition, place the plants apart by at least 2-3 feet to allow good airflow. 

3. Ventilation


Proper ventilation determines whether you grow huge autoflowering plants with good yields or duds with popcorn buds. Ample ventilation can help regulate the temperature and humidity in the grow room and maintain a healthy, balanced environment necessary for autoflowers to grow well. For instance, good airflow can dissipate heat generated by strong grow lights and maintain stable temps and humidity levels, thereby reducing the chance of pest invasions and mold. When you combine proper ventilation with stable temperatures and humidity, you have happy plants. 

In addition, good airflow will make the plants strong, prevents stagnant air, and discourage pests and other diseases. Avoiding pockets of stagnant air is very important as they encourage mold. In addition, good airflow will strengthen the stems of the plants indoors, just like they sway happily when there’s a good breeze outdoors. And, this motion helps the stems become stronger and thicker, reducing the risk of them toppling over. You can achieve this by placing fans around the plants but don’t position your plants directly in front of the plants as they will struggle. 

One way to efficiently maintain airflow is to introduce oscillating fans in the grow room. These fans are especially helpful as they aren’t too strong and provide continuous air movement for the plants. They mimic a gentle breeze indoors the plants will love when growing outdoors. You can also keep these fans near the lower branches that typically don’t get much air. 

Apart from oscillating fans, you can also use exhaust and intake fans to bring in gusts of fresh air and expel all the stale air. These systems will ensure there’s a consistent airflow within your grow room. 

Just like everything else, remember to maintain a balance even with the airflow. For example, if you use too many fans or extremely strong fans that throw gusts of air with a lot of force, the plants can get damaged. If the plants are continuously subjected to airflow that resembles strong winds, they can dry up pretty quickly. So, remember to maintain mild airflow at all times. 

Monitoring and adjusting the airflow within the grow space is an ongoing process. You should assess the conditions regularly and make any adjustments as the size and canopy increases to help the plants grow well. Thus, you may have to adjust the fan speed, add more fans or reduce them as necessary. 

When growing outdoors, you have little control over the airflow as well. However, you can choose locations that encourage your autoflowers to grow well. For instance, plant your autoflowers in areas where it’s not too windy. A fence would help. You can also use trellises to add extra support. Again, space the plants properly for optimum airflow. 

4. pH


You must always maintain an ideal pH range if you want to grow high-quality autoflowers. If you’ve grown cannabis already, you probably already know the importance of pH. If you’re new to growing cannabis, know that pH is nothing but the level of acidity or alkalinity of the growing medium that determines how the plants take in nutrients. 

The pH will also vary depending on the type of growing medium you use. For instance, if you’re growing in soil, maintain a pH between 6.0 to 7.0 to ensure the plants have no problem absorbing nutrients. 

Cannabis plants, including autoflowers, love slightly acidic mediums, so it’s imperative you maintain this range. If you go beyond this range, the plant will not be able to absorb nutrients efficiently, leading to various deficiencies. This means that the plant can struggle even if you provide nutrients.  

Since pH is extremely important, it’s best to get digital pH testers that give an accurate reading. Make sure you check the pH before and after administering nutrients as there will be a change. If you notice the plant experiencing deficiencies or any other problems, check the pH first as most issues can be solved by correcting the pH. 

To increase or decrease the pH levels, you can use pH UP or pH DOWN that’s available in most nurseries or online. Also, remember to change the pH gradually as sudden changes can disrupt the plant’s development. 

If you’re growing hydroponically or using soilless growing mediums like coco coir, the pH will need to be between 5.5 to 6.5 for all cannabis plants including autos. Again, this range ensures that the plants can absorb nutrients without any issues.

As a hydroponic grower, you need to especially monitor the pH regularly as the plants depend solely on the nutrient solution you provide. Therefore, you must track the pH levels frequently using pH meters. Adjust the pH as and when necessary using solutions created specifically for hydroponics. 

Just like soil, the plant will not absorb nutrients if you deviate above or below the recommended range. Many nutrients become unavailable for the plant, leading to various deficiencies, leaf discoloration, and stunted growth. 

5. Light


Light is crucial in cannabis cultivation, whether you’re growing autoflowers or photoperiod strains. The only difference is that while photoperiods need specific light cycles to progress into the flowering stage, autoflowers don’t make any such demands. Nevertheless, autoflowering plants need ample light to carry out photosynthesis like any other plant. 

Autoflowers will be happy with about 18 hours of light during the vegetative stage. You can continue with the same light cycle even during the flowering phase as well; however, some growers experiment with 12 hours during the flowering phase. Of course, the yields will be great if you provide 18 hours throughout the life cycle. 

Make sure you provide a grow light with high intensity. However, note that it shouldn’t be extremely high as the plants can suffer from light stress and light burn if you overdo it. Insufficient light intensity, on the other hand, can result in stretched and weak growth. Use light or PAR meters to ensure the plants are getting appropriate light. These meters measure the intensity and quality of light, and you make adjustments accordingly. 

Speaking of light intensity, go for about 300 μmol to 700 μmol when the plants are in the vegetative stage. In the flowering stage, you can increase it to about 1200 μmol. However, remember that while some strains will appreciate such high light intensity, others may start bleaching. Thus, you have to be aware of your plant’s reactions and adjust the light accordingly. Also, expose your plants to high-intensity lights gradually instead of doing it all at once. 

6. Nutrient Levels

Nutrient levels

Appropriate nutrition is important for growing healthy autoflowers. Providing the right balance of macro and micronutrients throughout the plant's life cycle is crucial. A good rule of thumb is to maintain EC levels between 0.75 to 1.0 when the plants are in the seedling stage. During the growing or vegetative stage, the levels need to be between 1.3 to 1.7. When they start flowering, you can go up to 2. The issue is that there are no optimum standards when it comes to growing marijuana, so the levels may vary depending on the strain, growing medium, and your growing conditions.  

Like photoperiod plants, autoflowers also require slightly higher levels of nitrogen during the vegetative phase to support the development of robust foliage and roots. 

Nitrogen also helps with chlorophyll production and overall plant growth. At this stage, go for balanced nutrient solutions with a higher nitrogen ratio, such as those labeled for vegetative growth for best results. Usually, most companies name this solution as “Grow” to be used during the vegetative stage. 

As the plants go into the flowering stage, the nutrient requirements shift towards higher levels of phosphorus (P) and potassium (K) that are best for bud formation, resin production, and overall bud development. Thus, you will have to use a nutrient solution formulated specifically for the flowering stage with the appropriate balance of macronutrients and micronutrients. Typically, this will be labeled as “bloom” if you’re using a two-part nutrient solution. 

Also, you must monitor the nutrient levels in the growing medium throughout the life cycle to avoid nutrient deficiencies or toxicities. 

7. Water Quality

 Water Quality

Water quality plays a crucial role in the overall health and growth of autoflowering cannabis plants. The quality of water used can influence nutrient availability, pH stability, and overall plant vitality.

Ideally, the water you use should have a neutral pH or be within the acceptable pH range for the specific growing medium. Adjust the pH of the water, if necessary, to ensure that the nutrient uptake remains optimal.

Coming to the type of water you can use, keep in mind that the water sources can vary in mineral content and also potential contaminants. High mineral content or excessive levels of certain elements in the water can block nutrient absorption, leading to nutrient deficiencies. If the water source contains chlorine or other chemicals that are common in tap water, just allow it to sit for at least 24 hours before using it so the chlorine can dissipate.

If you’re using filtered or purified water, or properly treating tap water to water your autoflowering plants, you can expect great results. It is best to regularly check water quality and pH levels to maintain a healthy growing environment.

8. Carbon Dioxide (CO2) 

Carbon Dioxide (CO2)

While it’s not imperative to use carbon dioxide, it can significantly influence the growth of cannabis plants. CO2 is an essential component for photosynthesis, and higher levels can lead to faster growth and increased yields. However, keep in mind that since autoflowers have a short life cycle, you may not see a dramatic impact that can be observed in photoperiods. 

If you still want to use it, you can supplement CO2 to your autoflowering plants using CO2 generators or tanks in your grow room. But, always remember to maintain CO2 levels within the appropriate range, typically around 700 ppm during the vegetative stage and about 1200 ppm during flowering. 

Outdoor growers generally have sufficient ambient CO2 levels. However, ensuring proper ventilation and airflow in outdoor settings can help the plants get more CO2. 

Summary: Optimal Growing Conditions: Exploring Ideal Environmental Factors for Cultivating Autoflowering Cannabis

Cultivating autoflowers can be very rewarding if you provide optimal growing conditions. However, you have to focus on key factors. First, maintaining proper temperature levels throughout different growth stages is essential. You can do it by using air conditioners or heaters, depending on your needs. 

Next comes humidity. Adjust the humidity using humidifiers or dehumidifiers according to the growth phase, from seedling to flowering to support nutrient uptake and reduce the risk of mold or other fungal problems. Adequate ventilation is equally crucial to create a balanced environment, ensuring proper airflow, controlling temperature and humidity, and strengthening the plants.

Always remember to maintain appropriate pH levels so the plants can absorb nutrients efficiently. By doing so, you will prevent nutrient deficiencies to a large extent. 

Then, you also have to provide sufficient and high-quality light during the vegetative and flowering stages for photosynthesis and bud development. Autoflowers benefit from about 18 hours of light throughout their life cycle. 

Provide balanced nutrition including macro and micronutrients according to the stage of growth to keep your autoflowers happy. Finally, while supplementing CO2 can benefit the plants, it’s not essential and you may not have as significant an impact on autoflowers due to their short life cycle.

Achieving mind-blowing autoflowering cannabis growth requires paying careful attention to temperature, humidity, ventilation, pH levels, light, nutrient, and water quality. By creating the ideal environmental conditions, you can maximize yields and enjoy the buds. 



For lighting, DLI is a better unit of measurement because of varying light cycles used by different growers. 24 hours of light needs to be a lower intensity than 18 hours and it makes all the difference, in my experience.


@FoTwenny, i use a 16/8 cycle in vege to better overlap my cheaper electricity hours. There's no difference as long as the DLI is the same for any common sense choice of light cycle - all other factors equal.

autoflowers.. blech :P just put a photperiod into 12/12 after 2 weeks and it's the same thing, lol. ... better, even.. probably more consistent size results and easier to fill your space properly - all just as long as a typical autoflower grow would take.


the npk stuff is not researched nor proven.. bunch of conjecture..

sure, you can amp up to 2.0 ec temprorarily... thta doesn't mean the plant's metabolism is matching it.. keep it up long term and you create a tox issue almost guaranteed. it may even look gret for 2-3 weeks after amping up, but it will happen.. and if it does that just means you pissed away a bunch of nutes down the drain.

just as taking a vitamin C pill above, i bleieve 250mg, is just going to pissed out because your body cannot metabolize more than 250mg per day. the plant has no excretion system, so it can only build up if it is supplied above the rate it can metabolize it.

i find the plant has the same tolerance of p and K in both vege and bloom. going over a particular threshold, relative to my local variables that are quite consistent, will eventually result in toxicities.. sometimes they take 6-8 weeks to form... a slow build up just means i'm feeding slighty above metabolic rates.

this is messy and complicated... esoteric to some extent because of so many variables. ratio, concentration and ph are all suprememy important. you can't just amp up 2 of the nutes without other changes due to various stimulative and antagonistic relationships involved. these are old urban myths (e.g, 'boost pk in bloom' or 'flush before harvest') that were never substantiated with evidence. it's folly to trust them.

research based fertilizers (soluble stuff you can use outside or with hydro) don't do these things, because the reserach doesnt say to do it... one is a top-down inductive nonsense and one is bottom-up deductive reasoning... the latter is a far better way to figure things out and more reliable conclusions.


Can we please… fix the GOT DAM site bugs. I’m done permanently after this set of diaries because it’s a fucking hassle each time. I have warned my sponsors to avoid handing out sponsorships tied to this site because of these issues, and have suggested others warn their sponsors as well.