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Autoflowering Cannabis - Pros and Cons

Created by
JoshuaHolt JoshuaHolt
Added 8 October 2020

Autoflowering Cannabis Plants Can Produce Resinous Flowers

In today's day and age, we have so many strains on the market that it can be a daunting choice to decide which plants are best. Autoflowers have gained traction over the recent years and are now a popular choice among growers of all levels for their ability to produce quick harvests. This article goes over the pros and cons so you can decide if autos are for you.

Like photoperiodic plants, each autoflowering strain has its own unique traits that make them slightly different to one another. Some may be more potent, whereas others might have more flavour or have a shorter life cycle. Whatever the goal is, autoflowers can make a perfect addition to any cannabis hobbyist's garden. If you've never grown before but are wondering where to start, autoflowers make a great entry point.

What Are Autoflowers?

The first thing to understand is what exactly autoflowering cannabis plants are. Basically, autoflowers are plants that do not rely on a photoperiod and flower automatically within a set period of time. Regardless of the exterior environment, they depend on their own genetic maturity as a way to reproduce. Blooming can arrive in less than a month after germinating.

Photoperiodic plants need a change in light to know when they need to flower. A cannabis plant has a vegetative cycle and a flowering cycle. The flowering cycle usually begins when the hours of light signal it to do so. Outdoors this is determined by the seasons and the dip in the sun's course towards the end of summer/beginning of autumn. Autoflowers have adapted and moved past this necessity, growing flowers when they are the right size, not when the light changes.

Autoflowering Cannabis Has Many Benefits

Autoflowering cannabis plants now thrive in the ever growing, fast paced world we live in. Their versatility means decent plants can be grown by almost anyone in a wide variety of locations. They make great balcony plants or would probably fit into that unused cupboard you were wondering what to do with.

The History Of Autoflowers

Autoflowering cannabis originates from the ruderalis family, hence its ability to live its cycle in a short amount of time. Ruderalis is a subspecies of cannabis like indica or sativa, but has a completely different background. The automatic flowering stems from how ruderalis strains were able to adapt themselves to the short growing seasons in colder climates such as those found in Russia, Eastern Europe or Asia. 

Differences Between Ruderalis, Sativa and Indica Leaf Structure

The autoflower gene developed as a way for plants in these regions to grow and flower automatically before the arrival of the harsh conditions of winter. This trait evolved to the point where the ruderalis strain no longer needed to 'understand' the change in daylight hours. Rather, they placed more importance on adapting to survive and reproduce in the short frame of time available to them.

Auto Vs Photoperiod

As we just discussed, autos aren't the same as photoperiods because they flower automatically. But is one better than the other? Unfortunately, there is not one answer to this question. Autoflowers will be better in some situations whereas photoperiodic plants will win in others.

One of an autoflowers' most attractive features is the short flowering times. Long grow cycles require more time, effort and money which can be an inconvenience for some. Even though photoperiodic strains take longer and use more nutrients, the investment can pay off with heavier yields at the end of it.

Photoperiodic Cannabis Plant

Most cannabis seeds found today are bred to be 'feminized' which means they have an almost 100% chance of producing buds. Autoflowers can also be feminized, so the main difference we want to focus on here is more to do with the photodependancy of a cannabis plant.

A photodependant cultivar can be grown to the desired size before putting it into flower. Indoor plants can be kept in their vegetative phase until you decide to change the light schedule from 18 hours per day to 12 hours per day, or transplant outside.

You do not have this same control with autoflowers. They flower regardless of whether they are grown under 18 hours of light or 12 hours of light, and can thrive even with just a few hours of light each day. An autoflower will look after itself as long as it receives enough light, water, air and the right nutrients.

Outdoor Autoflowering Cannabis

Due to the ruderalis heritage, it is actually possible to grow autoflowers under 24 hours of light. However, there is not much benefit to this other than keeping a plant shorter. Plants need to rest in order to function correctly, so it might be counterproductive to use this method. It's also more expensive and your lights won't last as long if they have to run constantly.

In terms of appearance, there is a noticeable difference between autos and photoperiods; their size. When grown under the correct conditions, autoflowering cannabis plants are usually smaller than photoperiodic strains. Because they grow and flower so fast, there is no time for them to reach the same level as their photoperiodic counterparts.

Grow Tip: If you're growing in pots, it is recommended to keep autoflowers in the same container for their entire life. Transplanting can slow the growth of an autoflower, which may affect final yields.

The Pros of Autoflowers

Growing autoflowers is probably the easiest way to introduce yourself to cannabis cultivation, and there are many reasons why an experienced grower may choose to give them a try as part of their horticultural practice. The positives almost certainly outweigh the negatives, but let's discuss both to find out why.

  • Quick Cycles - Compared to indica or sativa strains, autoflowering plants are fast flowering, meaning more harvests per year. Small plants with fast cycles are ideal for farmers under pressure to make a turnover in the commercial industry. Depending on the strain, an autoflower can be grown from seed to harvest in under 10 weeks. If you want bud quickly, autoflowers are the way to go. 
  • Easy Maintenance - Shorter grow cycles means less risk of problems, making them well suited to beginners. Light cycles do not need to be changed and maintained as they do with photoperiods. Light leaks during the dark hours are also less of an issue when growing autoflowers because they are not photodependent.
  • Resilient - Due to their genetic history, autoflowers are capable of withstanding harsher conditions than photoperiodic strains can, such as colder temperatures. This natural defence system helps to protect them against molds or pests.
  • Small/Compact Size - The size of a cannabis plant can become inconvenient, especially for an indoor grower. Autoflowers do not usually grow taller than 80 - 120 cm, making them perfect for anyone wanting to grow but with limited space. A bushy structure helps to support big buds later on.
  • Fewer Nutrients - Autoflowers require nutrients but due to their small size,  need nowhere nearly as much as photoperiods do. Larger plants with longer cycles inevitably need more feeding, however autoflowers can do well even with low doses of fertilizer. Using less nutrients also saves you some extra costs in the long run.
  • High CBD - The cannabinoid profile of autoflowers has shown that CBD content is often higher in ruderalis autos than in photoperiodic strains. This is beneficial for those looking make extracts or to use cannabis for medicinal purposes.
  • Stealthy - Depending on where you live, sometimes it is best to keep your green garden hidden. If you are trying to be stealthy, then consider growing autos. Their size and speed means they fit in all sorts of places without being noticed.

Some Autoflowering Cannabis Can Be Grown In Under 10 Weeks

The Cons of Autoflowers

Although the benefits of autoflowers may seem appealing, there are some important drawbacks which must be taken into consideration. If you have a history of growing indica or sativa seeds, make sure you understand how they differ from autoflowers. Not all growing techniques that work for photoperiodic plants apply to autos as well.

  • Lower Yields - Considered as a drawback, but is made up for through amount of harvests that can be achieved each year. Autoflowers produce the maximum they can in their short cycle. Being small plants, they are simply unable to grow as big as photoperiodic strains.
  • Mistakes Hard To Correct - Because they grow quickly and are dependant on time, any problems autoflowers come across could be hard to fix without affecting growth and yields. Although easy to grow, autoflowers need the correct conditions to avoid any issues.
  • Higher Lighting Costs - Autoflowering plants are normally grown under 18 hours of light for their whole cycle. They can even be grown under 24 hours of light, however this is not ideal if one is trying to keep electricity costs down. Obviously, outdoors this would not be an issue.
  • Do Not Handle Training - Performing high stress training techniques such as pruning, defoliation or topping can massively affect yields as the plant doesn't have enough time to recover, resulting in slow growth. Low stress techniques can work with autoflowers but should be performed with care.*
  • Bad For Cloning - Clones are exact copies of their mother. If a clone is taken from an autoflowering plant, the clone will be at the same stage as the mother, meaning it won't recognise that it has to reset its cycle. You may be able to root an autoflower clone, but it won't produce an exciting plant. Full maturity will be achieved before the plant has even finished growing or developing buds.
  • Less THC - Due to their size, autoflowering plants produce smaller buds than photoperiodic varieties. The ruderalis gene is excellent for its ability to automatically flower a cannabis plant, but not great in terms of THC content. For a long time this meant autoflowers were known to be less potent. Saying that, there are now plenty of autoflowering strains on the market that have more than enough THC to keep a stoner happy.

*Note: Be careful when applying LST (low stress technique) on autoflowers. They can handle slight manipulation but too much may be stressful for them. Over doing it can cause slow growth, undersized plants and underwhelming harvests.

Choosing the Right Strain

Choosing the right strain for your cannabis grow can be a little confusing in the beginning. You must consider your grow space and be realistic with your goals. Growing cannabis isn't just about cultivating the strongest strains with the biggest yields. Most of the success comes from understanding your plants' needs and adjusting your schedule accordingly.

Whether you are growing indoors or outdoors, not all autoflowers will perform in the same way. Autoflowers have been cross bred with indicas and sativas to create hybrid strains that have inherited the best characteristics of both. Now we have the possibility to choose fast flowering strains that are also full of terpene rich flavours derived from some of the most classic genetics.

High Yielding Cannabis Autoflower

Autoflowers are great for making efficient use of your available space, however some growers prefer to work outside if the environment permits them to. You might choose an indica dominant autoflower to keep things as compact as possible. Or you might have enough room to go for slightly bigger sativa dominant plants, but also be looking for short flowering times.

If you live in a particularly cold climate where the days are short (less light), growing autoflowers could be a wise choice to increase the chance of a successful harvest. A cloudy or rainy day outdoors won't phase an autoflower too much if you choose a robust, resilient strain. You can look out for the following traits when deciding which autoflowering strain is best for your grow:

  • Resistance to Mold
  • Low Chance of Pests
  • Best Outdoor Climate
  • Yield Indoors/Outdoors
  • Short Flowering Times
  • Indica or Sativa Dominance
  • Feminized Seeds

Feminized Autoflowering Seeds

With all that being said, it is important to obtain your autoflowering seeds from a reputable source. Seed banks that specialise in autoflowers or have an impressive breeding history are recommended. An experienced breeder will often have a good selection of genetically stable, feminized seeds to choose from.

It doesn't matter whether you are growing indoors or outdoors, you need to make sure that your selected strains are suited to the environment you plan to grow them in. Like all cannabis plants, autoflowers require your love and attention. Take care of them properly and they will reward you with lots of resinous buds in no time.

Cream Cookies Auto by StickyFingah from GrowDiaries


If you are just starting your growing adventure, autoflowers are highly recommended. As a beginner, it can be quite demotivating to experience all kinds of problems when all you are trying to do is harvest some tasty nugs. Trying your hand at cultivating autoflowers gives you the opportunity to have a smooth grow without worrying too much about failure wasting your time and money.

Autoflowering StrainCycle (Seed To Harvest)HeightYield (gr/m2)
Purple Lemonade - Fast Buds40 - 50 Days70 - 110cm400 - 500 
Think Different - Dutch Passion65 - 75 Days90 - 100cm450 - 500
Sweet Skunk Auto - Sweet Seeds45 - 55 Days60 - 90cm400 - 500
Glue Gelato Auto - Barney's Farm65 - 70 Days90 - 120cm550 - 600
Amnesia Auto XXL - Dinafem75 - 80 Days100 - 130 cm450 - 500
Strawberry Pie - Fast Buds65 - 70 Days60 - 100cm500 - 550
Royal Cheese - Royal Queen Seeds65 - 70 Days90 - 100cm425 - 475 
Cream Cookies - Fast Buds65 - 75 Days60 - 90cm400 - 500
Kalashnikova - Green House Seeds55 - 65 Days80 - 100cm750 - 800
Cream Caramel Auto - Sweet Seeds55 - 60 Days40 - 90cm350 - 500

If you have any comments on your successes or failures with autoflowering cannabis, feel free to share them in the comments section down below.

External References

A Rapid Method for Cannabis Species Determination by DNA Sequencing. ATLAS Biology. - Lightfoot, David & Throgmorton, Winston & Johnson, Colton. (2016).

Chemotaxonomy Of Cannabis I. Crossbreeding Between Cannabis Sativa and C. Ruderalis, With Analysis Of Cannabinoid Content. - Economic Botany. Beutler, John & Marderosian, Ara. (1978).

This article was updated September 2020.



I grow everything outside and I started growing autos about four years ago. I always shoot for the earliest time I can get them in the ground without freezing which in my area is Mid to Late April. I have my spot cleaned and cleared, compost in and ready to go for all my garden. I want to have them mature and ready to harvest by early July. After that the heat and sun can cause some issues on certain strains during the flowering stage. I don’t use containers because I have lost plants to wind damage, deep rooted plants withstand better and the transition from Spring to Summer can get nasty.


I grow autos indoors in hydro system an they fly! Just don't mess with them there doing there own thing an your just there adding what they need. 7oz a plant is easily achievable. If it's your first grow with an auto I recommend just letting it grow no LST just take a few leaves off that are blocking bud sites after week 4.
An as for the potency of autos they put me to sleep so happy days.
Works for me happy growing :v::skin-tone-3: