How to grow cannabis indoors

Growing cannabis indoors allows the grower to optimise lighting, temperature, humidity, air flow, nutrients and other key environmental factors. Indoor cannabis growing also allows you to control pests, something that the outdoor grower can’t always guarantee. The result is that well grown indoor cannabis can reach the very highest quality levels. No wonder that millions choose to grow weed indoors with the finest cannabis seeds and best grow room conditions. Whether you are a beginner aiming to start the right way or a skilled grower searching for the best ways to optimise the quality of your crops, this essential indoor cannabis cultivation guide is a keeper!

What are the key benefits of cultivating cannabis indoors?
How to plan your indoor cannabis grow from seed to harvest
What is the best initial setup and equipment needed?
What is the ideal space to grow cannabis indoors?
How to choose the best cannabis seeds for indoors
How to set up your indoor cannabis grow room
Indoor cannabis plants feeding schedule

Indoor cannabis cultivation benefits

Glueberry OG grown indoors under led grow lights

Outdoor/greenhouse cannabis growing has plenty of pros but a few occasional challenges such as cloudy/stormy weather, cool conditions, pests and other risks. Indoor cannabis growing may be more expensive due to electricity prices and the purchase costs of the tent, LED, fan, filter etc.

That being said, a high quality and well thought-out indoor grow room allows the grower to push every last bit of genetic potential from their cannabis seeds by optimising all the conditions and removing any limiting factors which might limit growth.

Get your indoor grow conditions right and you can look forward to the best possible quality levels with a terpene profile that will make you gasp in delight and cannabinoids that will refresh your soul with memorable pleasure.

When planned and executed well, growing cannabis indoors allows you complete control over all key cultivation parameters. Avoid over watering, avoid over-feeding, get a stable grow room, a quality LED light with good cannabis seeds and you should get top quality results.

Indoor cannabis growing stage by stage

Watching your cannabis seeds germinate and grow into mature female plants is a great joy and source of satisfaction. Many cannabis growers enjoy the experience of growing just as much as they enjoy the harvest! Growing cannabis indoors is often more than just a way to be self-sufficient in premium quality, low-cost buds. It’s an absorbing and rewarding hobby in which continual improvement & learning provides great fulfilment.

Photoperiod feminised seeds remain the preferred choice for many. Once germinated, the seed transitions through several different stages of life before harvest, typically 3-4 months later.

Less experienced growers may prefer the simplicity, speed, convenience and wide-growing latitude of autoflowering cannabis seeds. Autos typically grow from seed to harvest in around 11 weeks, thats often a few weeks faster than photoperiod feminised seeds.

Old school growers often enjoy the experience of growing regular cannabis seeds, selecting male and female offspring for further growing/crossing.

For many growers, the last week or two of growth is perhaps the most enjoyable and rewarding part of the grow. Monitor your plants well, check trichome appearance (clear/milky/amber) and harvest when the effects are perfect for you. Take your time to cure the buds well and look forward to cannabis quality levels that far exceed anything you can buy.

Indoor cannabis initial setup and equipment

When growing cannabis indoors many self-sufficient growers opt for a grow tent around 1.2m x 1.2m (4ft x 4ft) and will match the fan, filter and light to that sized tent. An indoor grow room complete with quality LED, fan, filter etc will set you back around €/$/£1000 or more.

That can seem excessive for some, who opt for cheaper systems with HPS lights and budget fan/filter combos. If funds are initially limited, you can always progressively upgrade your grow room as your passion and experience improve. Indeed, continuous grow room improvement/investments is precisely what many growers love to do.

One final thought, spending €/$/£1000 or more setting up a new grow room with an LED may seem expensive, but the costs are likely to be repaid from the value of the first harvest.

When growing cannabis indoors it can pay in the long-term to equip yourself with the best available equipment. This can save cash on inevitable future upgrades. Many growers often like to increase the size of their grow tent once they realise how much satisfaction they get from the process of growing their own cannabis – something to consider when deciding the initial grow room set up.

What is the ideal space to grow cannabis indoors?

Many growers have limited options when it comes to growing cannabis indoors. Often bedrooms are used, with the exhausted air vented indoors (not ideal, but often done).

If you do have options it pays to choose a room which doesn’t see large temperature variations and doesn’t suffer humidity issues. The following considerations are worth contemplating when choosing the best place for your indoor cannabis grow.

Choose the best area you can for your indoor grow location recognising any restrictions or limitations that may place on your grows. Loft growers may not be able to grow all year round, for example.

How many cannabis plants per square meter?

How much space do I need when growing cannabis indoors?
1.2m x 1.2m / 4ft x 4ft tends to be typical for many self-sufficient home growers. This can allow space for 4-5 large plants and approximate yields around 400-600g depending of course on many factors including light, cannabis seeds, length of veg time, grower experience etc.

Dutch Passion cannabis seed finder

Choosing the best cannabis seeds for indoors

The Ultimate feminised seeds late flowering harvest time big buds scrog field highyield massive colas

Cannabis genetics play a huge role in determining the quality of your harvest. Even the best equipped grow room in the world won’t be able to deliver high THC results from low-end cannabis seeds.

You may spend around 3 months, or more, growing your seeds. Therefore, don’t be afraid to spend the necessary time contemplating the various options available to you. Competent cannabis seed suppliers should offer you detailed expectations of likely potency levels, plant size, yield and effects.

Regardless of your preferences, always select cannabis seeds based on your situation and requirements. Smart growers often look at online grow reviews as part of their research before making their final choice. Experienced growers can find that plant training techniques (low/high stress training) can greatly improve productivity and yield.

How to set up an indoor cannabis grow room

semi hydro autopot xl system with clay pebbles and coco

If you’re upgrading your grow room, or setting one up for the first time, you may feel a little overwhelmed with the endless array of options. A knowledgable local grow shop owner is often a great source of advice. Some online grow shops also offer solid advice.

In general, less experienced growers may find it easier to initially opt for simpler options. Beginners may find it considerably easier to grow their cannabis seeds in large-aerated containers of soil with slow-release organic nutrients (e.g. BioTabs) rather than attempting a hydroponic SCROG.

Research your options carefully, recognising the strengths and limits of your own experience/situation and remember you can always upgrade your grow room (and grow style) as your confidence and experience evolves.

1. Choose the best-suited growing containers

Cannabis seeds can be grown in most types of grow container so long as the basics are present i.e. nutritious moist soil. But experienced growers have known for some time that those containers that offer maximised levels of root aeration tend to produce the healthiest root zones and therefore the largest plant with heavy yields.

Many professional cannabis growers, alongside serious self-sufficient growers, feel they get superior harvest quality/quantities when using aerated grow containers such as air pots, felt sacks or similar. These allow great levels of root oxygenation that standard non-aerated containers. Cannabis roots need oxygen to survive and thrive. By increasing oxygen levels in the cannabis root zone healthier, stronger growth is achieved.

Even when growing in a highly aerated grow medium such as a light-soil mix or coco fibre, root aeration and overall growth rates are benefitted by the use of an aerated grow container. Some growers push root aeration to the max, for example growing cannabis in coco fibre/air pot in combination with an air-stone at the bottom of the air pot.

What is the best plant pot size for cannabis?

When growing cannabis give serious attention to the use of grow containers that allow extra levels of root aeration (air pots, felt sacks etc). By allowing extra levels of root oxygenation increased growth/health of the cannabis root system will result. You can expect larger, healthier cannabis plants with heavier harvests and perhaps more potent buds.

2. Define a watering system

Mokum's Tulip (bottom plants) on a wilma drip system with a rockwool plug with coco inside and clay pebbles around.

A plant as flexible as cannabis can be grown with numerous different grow methods and watering systems. Which grow method best suits you will depend on a few factors.

How much complexity are you prepared to tolerate? How much automation do you want/need? How large is your budget? In general less experienced growers are advised to keep the watering system as simple as possible initially. Watering your plants manually is one of the more common methods, but there are a range of systems to suit all needs and budgets.

Perhaps the two most common errors seen when growing cannabis are the tendencies to over water and over feed. These errors are especially common among less experienced growers who may apply the (incorrect) logic that more water/food will produce larger plants.

The opposite is true, too much water will cause the cannabis roots to sit in an oxygen-deficient environment where they will eventually rot. Too many nutrients will burn the cannabis roots, permanently limiting future growth. Whichever grow system/medium you use, be sure to do all you can to keep your plants in the nutrient sweet spot, with neither under feeding nor over feeding.

Cannabis hydroponics produces very fast growth. As with every other cannabis grow method, best results are achieved when the cannabis plant is maintained in the nutrient sweet spot, with neither over feeding nor under feeding. This produces the stress-free conditions in which the plant can grow quickly and thrive – assuming all other growth factors (light, temperature etc) are also fully controlled and optimised.

3. Simulate the desired climate

How to grow cannabis in hot climates

No matter how good your cannabis grow system, you won’t get the best results unless you can create optimised conditions in which to grow your cannabis. This means getting temperatures, humidity levels etc optimised at each stage of growth. Remember the conditions required for your plants will vary greatly as she transitions from cannabis seed to harvest-ready female.

Ensuring an optimised, stable indoor grow climate for your plants is often one of the most overlooked areas of indoor growing. Pro-growers go to great lengths, often with adjustable extraction fans that keep grow room temperatures as stable as they can. Avoiding extreme heat/cold allows you to maximise THC levels and final bud quality.

4. Provide optimal lighting to your plants

Autoflower cannabis plant light schedule

Cannabis requires high light levels during bloom to allow the cannabis genetics to reach their full potential. Even high quality cannabis seeds will produce puny harvests and small buds when grown with inadequate light intensities. Choosing the right cannabis lights for your grow area and knowing how to use them correctly is one of the most crucial aspects of indoor cannabis growing.

Unfortunately there is a massive range of grow light technologies with prices from budget levels all the way up to professional grade LED. When it comes to the potentially expensive time to buy/upgrade your grow light it really is worth taking your time and considering the options carefully.

How to calculate your lighting needs?

Your grow light, especially if you opt for LED (the choice of most serious/pro growers) will probably be the most expensive part of your indoor grow room. Some growers are tempted to save cash and use a slightly underpowered light, but this is false economy since harvest amounts will be reduced.

When growing cannabis indoors many use a 1.2m x 1.2m (4ft x 4ft) tent. Often a 400-650W LED will be used, or perhaps a 600W HPS if a budget option is required. This will allow PPFD light levels of around 750-1000 μmol/m2/s which will allow optimised bloom. Professional grow light manufacturers will list the recommended hanging heights for their light at various stages of growth. They should also clearly explain the PPFD light intensities in grow tents of different sizes.

In depth guide to grow light PAR, PPFD, DLI and Wattage

Best types of grow lights for cannabis

Here are the main light choices for growing cannabis indoors.

Mounting your light fixtures

You have researched your light options carefully and maxed out your budget to get the best grow light you can afford. Now you need to make sure that the light is mounted correctly. Ensure that your light is hung level, some growers use a spirit level to ensure the light is level and illuminating the grow area evenly.

You also need to hang the light at the right height above the canopy. Your grow light manufacturer should give detailed hanging heights and (if necessary) the associated power levels.

Monitoring and adjusting your lighting

Many grow lights, especially modern LED lights, come with adjustable lighting. This allows the grower to slightly adjust/increase their grow light power as their plants mature. Few growers have a light meter that allows them to measure PPFD, instead they rely on their experience and the light manufacturers recommendations.

If you can afford it, LED is the preferred option for growing cannabis indoors. An LED grow light will function for thousands of hours with negligible intensity loss. Remember to get a light that will allow your grow room area to reach PPFD levels of around 750 (or perhaps more) to maximise bloom potential.

5. Achieve an optimal grow room air flow

Oxygen and Carbon Dioxide are two essential ingredients for the growth of cannabis. Ensuring a good air flow through your tent is another of the often overlooked aspects when growing cannabis indoors. Not only does all the air in your grow room need to be replaced perhaps 2-3 times every minute, but you will need circulation fans inside your tent to ensure no ‘dead spots’ of stale air.

Indoor cannabis grow room ventilation

Many home growers like to keep a spare carbon filter at home for the inevitable day when they notice their existing filter is starting to fail. For extra security some growers will position an ozone generator in the exhaust air stream. The ozone chemically removes any traces of cannabis aroma that managed to escape the carbon filter. As well as ensuring a good flow of fresh air into the grow room (to optimise plant health and minimise chances of disease) growers need to ensure that the exhaust air is scrubbed clean of any cannabis aromas.

Indoor cannabis grow room air circulation

Small clip-on fans are often used by growers to ensure that no pockets of stale air can remain in the grow room. These can also be positioned underneath the plant canopy, an area often neglected by indoor growers. Likewise, any dead foliage, fallen leaves, dirt etc should also be cleaned away. A little extra effort to ensure good grow room circulation can avoid problems later on.

Indoor cannabis grow room CO2 supply

Hobby growers probably needn’t worry too much about supplementing grow room CO2. It only really makes sense to introduce extra CO2 when the grower has eliminated every other bottleneck restricting growth. Often CO2 is used when grow room PPFD (light intensity) levels are at/above 1000

Most growers probably won’t need to worry too much about introducing extra CO2 when growing cannabis indoors. However some licensed/pro growers may find it cost effective.

Cannabis grow room ventilation guide

There is little purpose in buying the best cannabis seeds, LED grow light etc if your grow room suffers from poor air flow and/or poor circulation. Ensure an adequately sized extraction fan and a matching filter. Self-adjusting extraction fans that maintain grow room temperatures are often preferred by pro-growers.

6. Maintain a clean and safe environment

Keeping a clean and safe grow area takes very little effort at all, especially if the grower keeps on top of the grow room with basic housekeeping/tidying. Not only is it good growing practice to ensure a tidy tent when growing cannabis indoors, it can prevent pests/disease outbreaks saving the grower from future problems.

Cleanliness and safety measures

Never allow dead leaves and soil/nutrient/grow-medium mess in your grow room. Dead leaves/vegetation can allow disease (or pests) to take hold.

When growing cannabis indoors, problem prevention is always better than problem curing. Modern grow tents have wipe-clean surfaces allowing you to clean the mess up and wipe down the surfaces. A small hand-held vacuum is perfect for hoovering up any soil/coco-fibre dust.

Indoor cannabis odour control

Especially in countries where growing cannabis indoors is still illegal, growers need to take extra care to deal with any cannabis aromas. If not they risk broadcasting the presence of their grow room. Use of good quality carbon filters (and stocking a spare one at home, just in case) is always recommended.

Odour control when growing cannabis indoors

If a grower can keep a clean, well organised grow room they can avoid problems later and allow a pristine grow environment where they can grow the highest quality cannabis indoors. Ensuring your grow room has good odour management in place ensures maximum peace-of-mind

7. Soil and other media for growing weed indoors

Many people find soil is a simple, easy grow medium when growing weed indoors. Use a large enough volume of it (especially in conjunction with slow-release organic nutrients such as those from BioTabs) and you needn’t worry too much about needing to add mineral nutrients throughout the grow.

Plenty of other growers find coco fibre easy to grow in – perhaps with slightly faster plant growth compared to soil. But other options are available too, such as growing in fibre glass, rock wool (and mapito) clay pebbles, perlite etc.

Growing cannabis in soil is an easy way to get great results when growing cannabis indoors, whether you are an experienced grower or just starting. Many growers also claim that the richest cannabis taste comes from organic, soil-grown weed.

The best type of soil for indoor cannabis

Soil mixture vs organic vs coco substrate vs worm castings for cannabis

A good quality soil is light, aerated and contains the necessary nutrients and minerals to sustain plant growth. Often growers have their preferred soil blend from their local (or online) grow shop.

Numerous soil brands are available, some lighter options more suited to seedlings and fortified soil blends suitable for more mature plants. Some wood-free soil mixes claim to be free from pests such as fungus gnats and are popular with many growers.

All good quality pre-prepared grow shop soils should have a light fluffy texture, not too dense/heavy. The main brands all deliver good results when growing cannabis indoors.

The larger the grow container the greater the volume of soil your plant has. At the same time, large grow containers offer a large reservoir of nutrients which may sustain the plant into late bloom necessitating perhaps only a light top-dressing of bloom nutrients as the plant approaches harvest.

Many growers like to combine a reputable, good quality soil brand with an aerated modern grow container such as an air pot or grow sack. It’s not uncommon for containers of 50 litres+ to be used when growing weed indoors. Large, aerated grow containers favour the extensive root network necessary for growing the largest plants, often with minimal plant maintenance.

What type of soil is best for autoflower cannabis?

Aim for a large, aerated grow container (aim for 50-75 litres + if you have the space) of soil and supplement the soil with BioTabs slow release grow nutrients for an easy, uncomplicated grow experience. You will need to add little else (if anything) other than water until the end of the grow.

Growing cannabis indoors with coco fibre

Growing weed indoors using coco fibre has become very popular. Many adepts claim faster growth rates than those seen in soil, though not as fast as hydroponically grown cannabis. Coco growing usually requires a basic mineral nutrient mix made from a simple ‘Part-A’ & ‘Part-B’ nutrient blend.

As with soil, numerous reputable coco fibre brands are available. It is always recommended, especially for less experienced growers, to buy the more expensive washed/buffered coco fibre. Dutch Passion also recommend the use of slow release organic nutrients, e.g. BioTabs, with coco fibre which simplify the nutrient considerations even further.

Indoor cannabis nutrient feeding schedule

Use of nutrients is one area that can cause difficulties, and even disasters, for growers. Fail to provide enough nutrients and your plant will be unable to grow adequately and may show nutrient deficiencies. Growing cannabis indoors with an accidentally excessive nutrient regime is an even more serious problem, in the worst cases the plants will be permanently stunted or will die.

The holy grail of nutrient management is to understand the plants nutritional needs at each stage of growth and meet them without over-feeding or under-feeding. The goal is to maintain your plants in the nutrient sweet-spot from the germination of your cannabis seeds all the way though to harvest. This is easier said than done, experience plays a large part. It pays to start with low nutrient levels and slowly increase, backing off at the first hint of nutrient burn.

It’s also important to use reliable pH and EC meters, calibrate them regularly and have replacement meters ready for the inevitable day when the meter starts to fail and give erroneous readings.

Use of bottled mineral nutrients does require care and precision. Get things badly wrong and you could wipe out your crop quickly, especially if you are growing with hydroponics where the impact is immediate. Experienced growers tend to feel less daunted with the task of managing an array of specialist nutrients. Rookie growers often feel understandably cautious when it comes to bottled nutrients and many prefer the simplicity and fool-proof nature of slow release organics instead (BioTabs) which allow the grower to simply add water to their plants for much/all of the grow.

Best cannabis nutrients and feeding schedule

Complete confidence with nutrients/nutrient feeding schedules comes with experience. Get things badly wrong and you can damage your crop. Less experienced growers seeking an easy way to keep their plants in the nutrient sweet spot may wish to consider slow release organic nutrients in large aerated containers of soil.

Grow your premium indoor weed at home!

Auto Blackberry Kush amazing cannabis seeds bag appeal

Growing cannabis indoors at home allows you to enjoy premium quality buds at a fraction of the normal price. Most home growers would say that they can grow better quality buds than they can buy.

You can choose the genetics, grow them to their maximum potential with a solid LED light and harvest the plants at the point of your choosing. The grow process can be as complicated and hands-on as you wish. Or it can be a simple, easy process where you need do little else other than water your plants. It all depends on how you want to grow and how much control you want to take.

One of the easiest ways to grow cannabis indoors is in large aerated grow sacks of soil with slow release organic nutrients. There really is little to go wrong with this method!

However you grow, do your best to learn as much as you can along the way and try to incorporate continuous improvements to your grow room. Growing cannabis indoors is not just an affordable way to supply yourself with premium buds, it’s also great fun and an enjoyable hobby for millions of people around the world.

10 Comments. Leave new

  • Boitshwarelo Pico
    14/06/2020 18:04

    How close to put growing LED lights

    • It depends on the type/power of LED light you have, if its powerful start at 65cm for veg and bring it down to 45cm for flowering.

  • Rajeshwar Dayal
    10/10/2020 18:26

    More Blue light increases the number of female plants ?

    • We have not worked with this technique yet, but there are indeed theories out there that blue light in the vegetative phase could increase your numbers in female offspring.

      Dutch Joe

    22/12/2020 14:45

    There is some excellent advice in this article. Dutch Passion has been producing world class genetics for decades. Whether you are growing indoor or outdoor, Dutch Passion will have seeds to fit your needs =)

  • where can I find the black and green pot in the header or first image?

    • Hey,

      This is an airpot, you should check for yourself what the best options are to buy these 😉

      Dutch Passion

  • Michellis
    09/02/2021 17:31

    Is it possible to explain when the veg state stops and the flowering state starts. I suppose the answer is in the question, but I’m a little unsure…?

    • Hey,

      I am not sure if you mean with autoflowering or photoperiod varieties.

      But with photoperiod varieties the flowering period starts when the lights are switched from a 18/6 to a 12/12 light schedule.

      Autoflowers will start to flower automatically.

      Dutch Passion

  • Mike Mitchell
    11/02/2021 03:04

    I’m a first time growerAnd this was very informational for me


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