Knowing how to grow autoflowering cannabis plants indoors will ensure that you can produce superb harvests every time with little effort. Autos are much easier to grow than photoperiods due to their shorter life cycle, and are an excellent starting point for first-time or beginner-level indoor growers.

In this article, I will explain everything you need to know to grow autoflowers indoors successfully. Covering the importance of genetics, lighting, watering, the best soil and pots, optimal temperature and humidity range, common mistakes to avoid and how to increase your autoflowering yields.

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Why Grow Autoflower Seeds Indoors?

Most people think of autos and presume they are only for growing outdoors in a hot climate, and stick with photoperiods using 18/6 and 12/12 lighting schedules. Below highlights the benefits and differences of growing photoperiods and autos and why you may want to think about growing autos for your next crop!

Autoflower vs Feminised Indoor Growing: What Are the Benefits and Differences?

The first thing to know is that autos have a short vegetative period and will begin to flower automatically after 4 weeks from the day the seed sprouts. Photoperiods, on the other hand, are dependent on longer darkness periods to induce flower production, which is why indoor growers always follow the 18/6 and 12/12 schedule.

The only major difference you need to know is that cloning autos is not advised because the clones will begin flowering. Also, autoflowering plants do not respond well to transplanting. For this reason, we always recommend that you plant directly into a large-sized container and let the plant grow.

The table below compares the main differences between autoflowering and feminised photoperiod plants for indoor growers.

Feature	Autoflowering Cannabis	Feminised Photoperiod Cannabis
Flowering trigger	Flowers automatically with age	Requires 12 hours of darkness
Typical seed-to-harvest time	9-12 weeks	14-20+ weeks
Light schedule	18/6, 20/4 or 24/0	18/6 for veg, 12/12 for flower
Beginner friendly	Very beginner friendly	Better for growers with some experience
Cloning	Not recommended	Ideal for cloning and mother plants
Training time	Limited due to short veg stage	Longer training window
Plant size	Small to medium	Medium to large
Yield potential	Medium to high	Usually higher
Best for	Fast, simple indoor grows	Larger plants and maximum control

The Benefits of Photoperiods

Photoperiods can be kept in a state of vegetation indoors using 18 hours of light
You can clone photoperiod plants and produce a mother plant
Photoperiods allow a grower much more time to train them during the vegetative stage
Yields are typically greater using photoperiods due to plants being taller and wider
Outdoors, photoperiod plants planted in the spring can become massive when harvested

The Benefits of Autoflowering

Autos have a fast turnaround time, ranging between 9 and 12 weeks from seed to harvest, with some 60 day autoflowers finishing even quicker under ideal growing conditions.

Autos are low-maintenance and easy-to-grow plants
They are ideal for first-time growers or those with little experience
The quality of the buds autos produce is on par with photoperiods
Outdoors, they can be planted back-to-back during Spring until Winter
Autos produce short-sized plants, making them discrete and stealthy

How to Grow Autoflower Seeds Indoors Successfully

So if you are already liking the idea of growing autos indoors and are looking forward to a new challenge after years of growing photoperiods, then this explains why choosing the best autoflowering seeds, the correct light and watering schedule is so important for growing autos successfully.

Choosing the Best Autoflower Seeds for Indoor Growing

Everything starts with genetics, and choosing high-quality autoflower genetics is one of the most important steps for success. For new growers, starting with proven autoflower seeds for beginners can make the entire process much easier. What do I mean by the best autoflower seeds? With so many autos on the market, it can be difficult and slightly overwhelming to check every auto strain from every breeder. I would recommend planting several different autoflowering strains together. This way, you will see which strain was your favourite and the best performer.

Light Schedule and Grow Lights for Autoflowers

Whilst autos are not dependent on the light cycle, and one reason they are so popular amongst outdoor growers, you still want to provide your autos with plenty of PAR-rich, intense light. Now there are many different grow schedules you can pick; however, the most popular and cost-effective are 18/6 or 20/4. If you’re unsure which approach to follow, our guide to the best light schedule for autoflowers explains the advantages and disadvantages of each option.

You can grow autos with 24 hours of light; many growers find the dark period benefits their plants, lowers monthly electricity bills, and makes controlling temperature and humidity easier.

As far as lighting is concerned, the more intense and PAR-rich your grow light, the better! Do not waste your time using a CFL or an HPS that is less than 600W. LED grow lights, in my opinion, are far superior at delivering optimal PAR and spectrum with significantly less heat. Selecting the best grow light for autoflower plants can have a major impact on growth rates, bud density and final yields.

The table below shows the main autoflower light schedules and when each one may be useful.

Light Schedule	Daily Light Hours	Best For	Main Benefit	Possible Drawback
18/6	18 hours on / 6 off	Most indoor growers	Good balance of growth and energy cost	Slightly less total light than 20/4
20/4	20 hours on / 4 off	Maximising growth	Excellent balance for autoflowers	Higher electricity use
24/0	24 hours on	Experienced growers with good climate control	Maximum light exposure	More heat, stress risk and electricity cost

How to Water and Feed Autoflower Plants Indoors

Watering your cannabis plants correctly makes a huge difference to how well the roots and foliage develop. Autos do not require much water, especially during the first 2-4 weeks. We recommend only watering your autos regardless of the growth stage when:

The soil has become dry and dusty
The pot has become light enough to lift off the ground
1-2 hours after the grow lights have turned on
Your plants begin to wilt slightly

As far as nutrients are concerned, you do not want to overfertilise your autos, and considering that they do not require much nutrition during the seedling or vegetative period less is more.

During weeks 1-4, use a nutrient designed for the vegetation stage
From week 5 onwards, use a flowering feed higher in P and K
Use half of the recommended ratio of nutrients for autos

Use the table below as a simple indoor autoflower feeding guide.

Growth Stage	Approx. Week	Feeding Advice
Seedling	Week 1-2	Water only or very light root stimulant
Early vegetative growth	Week 2-4	Light vegetative feed
Pre-flower	Week 4-5	Gradually transition from grow feed to bloom feed
Flowering	Week 5 onwards	Bloom nutrients higher in phosphorus and potassium
Late flower / ripening	Final 1-2 weeks	Reduce nutrients or use water only, depending on your grow style

Best Indoor Setup for Autoflower Cannabis Plants

Once you have decided which autoflowering strains are best for you, the next thing to cover is the best indoor set-up for autoflowering cannabis. This means choosing the right grow tent and ventilation, using the best soil and pots, and creating the ideal growing environment, as explained below.

Choosing the Right Grow Tent and Ventilation

The size of your grow tent will depend entirely on how many plants you want to grow, how much space you have, and if you have to abide by your state plant count laws. Autos do not grow very big, so you can produce a good yield in a small space.

Use the table below as a general guide when choosing your indoor autoflower setup.

Grow Tent Size	Recommended Autoflower Plant Count
0.8m x 0.8m x 1.5m	4 plants
1m x 1m x 2m	4-6 plants
1.2m x 1.2m x 2m	6-9 plants

Proper cannabis grow room ventilation is crucial for allowing plenty of fresh air to enter the grow space while removing stale, hot air.

Exhaust fan: This is responsible for blowing air out of the top of the tent using aluminium ducting
Carbon filter: This connects to the exhaust fan and scrubs the air clean using carbon
Ducting: Made of aluminium, it connects the exhaust fan to the carbon filter
Chain and hooks: Used to securely hang the equipment at the top of the grow tent

Best Soil and Pots for Autoflower Seeds Indoors

If you are a beginner grower or new to growing, we always advise growing your autoflowering or photoperiod crops in soil. The reason is that soil is a very forgiving medium for growing smooth-tasting, chemical-free flowers. The key to producing a clean and flavoursome crop is starting with top-quality soil.

Good quality soil will have a fibrous, lightweight and spongy texture when squeezed
Check to see how well the soil drains after watering and how frequently it dries out again
Good quality soil should have a dark brown and black appearance with a shimmer
Avoid using soil that has high NPK levels, such as 10-10-10, as these contain chemical inputs
The aroma of fresh, top-quality soil will be sweet and earthy. Avoid soil with a bad aroma
If your soil contains worms that are actively moving around, then this is a great sign of good soil

You may be thinking, what difference does the pot I grow my autos in matter? However, you would be happy to know that some pots are better for growing cannabis than others, and can even improve root development and health, as well as impact yields.

Pot Type	Best Feature	Drawback	Best For
Plastic Pots	Cheap and reusable	Can become root-bound	Budget growers
Fabric Pots	Excellent root development	Dry out faster	Most autoflower growers
Air Pots	Maximum root aeration	More expensive	Advanced growers chasing bigger yields

For most indoor autoflower growers, fabric pots are the best all-round choice. They improve airflow around the root zone, encourage air pruning, and help develop a dense network of feeder roots. A 3-5 gallon (11-19 litre) fabric pot is ideal for most autoflowering strains, although choosing the correct pot size for autoflowers will ultimately depend on the genetics and growing space available.

Plastic Pots

Plastic pots are easy to find, cheap, long-lasting and can be washed and used after every harvest. The only downside to plastic pots is that they promote root formation, leading to a root-bound structure.

Fabric Pots

Felt fabric pots are great for growing autos or photoperiods because they create a layer of air around the edges of the fabric. This layer of air allows roots to move freely towards the fabric and become pruned, resulting in more fibrous root hairs. Fabric pots are well known for allowing plants to develop a prolific and extremely fibrous root base.

Air Pots

These pots may look strange, but they do an excellent job of allowing the soil and roots to breathe and prune, just as fabric pots do. Air pots may be the most expensive of these three options, but they are superb for producing high yields in small spaces and can be washed and reused each time.

Ideal Temperature and Humidity for Indoor Autoflowers

Autos will grow for the first 4-5 weeks, before they start to flower. With such a short life cycle, making sure that you have the correct temperature and humidity levels dialled in will be crucial.

Lights on, temperature and humidity = 24 degrees Celsius and 50-60%
Lights off, temperature and humidity = 18-20 degrees Celsius and 50-60%

Common Mistakes When Growing Autoflowers Indoors

On one hand, growing autos can be a totally stress-free experience where everything goes great. Then again, it can be easy to make mistakes that affect plant growth and development and harm the yield and flower quality. Below is a breakdown of how overwatering and overfertilizing can affect size, development, health, and yield potential.

Overwatering Autoflower Plants

Overwatering is one mistake I think every grower has made during their time as a cannabis cultivator. It only takes a little too much water, and the next thing you know, your plants are wilting, and the soil becomes soggy, waterlogged, and dense.

The trick to avoiding overwatering is to give your plants less than you think. My golden rule is to use the 10% rule. This means that I would give, for example, a 10-litre pot 1 litre of water or a nutrient solution. I only water again when the soil is dry, and the pots feel light to the touch.

The bigger your auto becomes, the more water it will demand, so gradually increase the volume of water/nutrient solution you give them. Doing so will prevent overwatering and overfeeding.

Using Too Many Nutrients Indoors

The idea of giving your autos as much food as possible to grow into a monster is a bad idea. Cannabis plants that are overfed can become stunted, cease growth, and begin to show signs of nutrient deficiencies and toxicity. Autos are more sensitive to nutrients than photoperiods. Using half the recommended amount will benefit autos and help maintain optimal plant health and vigour.

Why Autoflowers Stay Small Indoors

There are several different reasons why your autos may end up short in height and produce a yield far lower than you were hoping for:

Heat stress: Autos that suffer from heat stress due to hot and dry grow rooms can become small
Low light intensity: Low light intensity can cause plants to mature between 50 and 75cm in height
Overfertilization: Over-fertilised plants will grow much more slowly and produce lower yields
Small pots: Using a small pot less than 2 gallons will cause short autos

How to Increase Autoflower Yield Indoors

There are ways to increase the amount of buds your autos produce, and that is through plant training, environmental optimisation and selecting high yield autoflower seeds with strong genetic potential. You have to remember that, unlike photoperiods, you do not have the luxury of long vegetation and plant training. Below explains the best training technique for maximising yields, knowing when to correctly harvest and how to dry and cure your buds properly.

Low Stress Training for Indoor Autoflowers

Low stress training for autoflowers is one of the safest and most effective techniques for increasing yields without slowing plant development. LST involves tying down the top of the plant horizontally, allowing the side branches to grow upwards. This technique also enhances light penetration and airflow, helping to fill out your grow space efficiently.

When to Harvest Indoor Autoflower Plants

Harvesting your autos at the right time will allow you to achieve the best possible bud quality, potency and resin production, especially when growing high THC autoflower seeds.

The trichomes under a magnification tool appear milky and amber coloured
The buds are dense and compact when lightly squeezed
The plant is packed with resin covering the leaves and buds
The flowering time matches the number of weeks
The pistils are 80-90% brown or orange coloured

Drying and Curing Autoflower Buds Properly

There is no point in spending months of hard work only to have your autos poorly dry out. Drying your plants properly, followed by a professional-level curing method, will produce cup-winning buds that you will love to consume.

Cannabis buds can require 10-14 days to properly dry before being placed in jars
The drying room temperature should be as close to 15 degrees Celsius as possible
Maintain a humidity level inside the dry roof of 60%
There should be good air flow inside the dry room
Avoid blowing fans directly at hanging buds

Curing is the art of burping the jars your buds are stored inside. This involves removing the lid of the jar for 10 minutes a day. Doing so will create air exchange, improve flavour, and enhance potency. Growers can choose to cure their buds anywhere from 2 weeks to 6 months.

Fill your curing jars or plastic tubs 75% full
Keep them stored in a dark and cool place away from sunlight
Avoid shaking the jars and lightly move the buds around inside

Frequently Asked Questions About Growing Autoflowers Indoors

What is the best light schedule for autoflowers indoors?

Most indoor growers use an 18/6 or 20/4 light schedule for autoflowers. While autoflowering cannabis plants can grow under 24 hours of light, providing a dark period helps reduce electricity costs, makes temperature control easier and allows the plants time to rest.

How long do autoflowers take to grow indoors?

Most autoflower strains take between 9 and 12 weeks from seed to harvest. Some fast-flowering varieties can finish in as little as 8 weeks, while larger sativa-dominant autoflowers may require up to 14 weeks.

What size pot is best for indoor autoflowers?

A 3-5 gallon (11-19 litre) pot is ideal for most autoflower strains. Since autoflowers have a short life cycle and do not respond well to transplanting, it is best to plant seeds directly into their final container.

Can you transplant autoflowers?

While it is possible to transplant autoflowers, it is generally not recommended. Any stress during the early stages of growth can reduce plant size and final yields. For the best results, sow seeds directly into the final pot.

How much can an autoflower yield indoors?

Indoor autoflower yields depend on genetics, lighting, environment and grower experience. Under optimal conditions, most autoflowers can produce between 50 and 250 grams per plant, with some high-yielding varieties producing even more.

How many autoflowers can I grow in a 1m x 1m tent?

A 1m x 1m grow tent can comfortably accommodate 4-6 autoflowering plants. The exact number depends on the strain, pot size and whether plant training techniques such as low stress training (LST) are used.

Do autoflowers need nutrients?

Yes, autoflowers benefit from nutrients, but they typically require less feeding than photoperiod plants. Many growers start with half the manufacturer’s recommended dosage and increase only if the plants show signs of needing more nutrition.

Can you top autoflowers?

Some experienced growers top autoflowers successfully, but low stress training (LST) is generally the safer option. Because autoflowers have a limited vegetative period, excessive stress can reduce growth and affect yields.

Why are my autoflowers staying small indoors?

The most common causes of small autoflowers are overwatering, overfeeding, poor genetics, low light intensity, heat stress and growing in containers that are too small. Ensuring optimal environmental conditions from the seedling stage is essential for maximising plant size and yield.

What temperature is best for indoor autoflowers?

Autoflowers perform best with daytime temperatures around 24°C and night-time temperatures between 18-20°C. Maintaining stable conditions and avoiding extreme temperature fluctuations will help support healthy growth and flower production.

Are autoflowers good for beginners?

Yes, autoflowering cannabis plants are considered one of the best choices for beginners. Their fast growth, automatic flowering cycle and low-maintenance nature make them easier to manage than traditional photoperiod strains.

Do autoflowers produce as much THC as photoperiod plants?

Modern autoflower genetics can produce THC levels comparable to many photoperiod strains. Thanks to years of breeding improvements, today’s autoflowers are capable of producing potent, high-quality buds with excellent flavour, aroma and cannabinoid content.

How to Grow Autoflowers Indoors: The Complete Beginner’s Guide

Why Grow Autoflower Seeds Indoors?