Growing Cannabis Indoors: The Ultimate How-To Guide

Well, look at you. Ten years ago, we had to sneak around to get the stuff, and now you’re just browsing the Internet for a guide to growing cannabis indoors. If that’s not progress in our civilization, I don’t know what it is!

If you landed here, chances are that you’re looking for a step-by-step guide on how to grow marijuana at home. And I surely won’t bore you (delight you?) with the history of cannabis and its medicinal benefits. You can read this article instead if that’s something you’d fancy.

Here we intend to put a free comprehensive step-by-step manual on cannabis indoor cultivation at your disposal. What was that? You live in a tiny apartment? It doesn’t matter. Don’t have a green thumb? We’ll grow one of those too. So buckle up, and welcome to…

A Complete Guide to Growing Cannabis Indoors

Growing Cannabis Indoors VS Outdoors

But, why indoors? Could you maybe grow your cannabis plants outdoors? Growing cannabis outdoors versus growing indoors is a never-ending debate, with advocates from both sides praising the pros and holding back the cons. Truth is, both cultivation methods have advantages and disadvantages.

Outdoor Pros

On the bright side, you can expect a much higher yield when growing outdoors. Some cannabis strains will grow massively because they simply prefer an outdoor environment. Also, outdoor growing is less expensive. You have free light, space, nutrients, and CO2. What’s not to like?

Outdoor Cons

The downside here is that outdoor crops have a much longer gestation period. Most likely, you won’t be able to harvest your crop twice a year. Instead, you need to patiently wait for their natural life cycle. Also, don’t forget about your local area’s climate conditions. Heavy rainy seasons can lead to plant mold or bud rot. Excessive heat can also kill your crops. On top of that, think of storms, tornados, fires, pests, or predators -like deer- that could destroy your crops. It’s dangerous out there.

Indoor Pros

When growing indoors, you can play God and have absolute control over the light, temperature, and humidity. Thus, you spare yourself the stress of outdoor cultivation risks entailed by inclement weather. Another big plus of growing indoors is that you can expect up to 4 harvests a year, significantly exceeding the limited amount you get from outdoor crops. Also, indoor lights can grow beautiful flowers with high THC percentages. Finally, growing indoors helps you stay on the safe side in terms of law-abiding cultivation and will spare you dealing with your neighbors about it.

Indoor Cons

One of the indoor growing cons is that plants will definitely be smaller. Sunlight trumps any other artificial light source you may have for your plants. Another con is that you’ll need to prepare a space for cultivation and invest in a variety of tools and equipment. Replicating natural sunlight indoors can be costly, and your monthly energy bills will reflect that. So, if you’re on a very tight budget, this can be a major setback

The Best Place to Grow Cannabis Indoors

What is the best place to grow your cannabis indoors? Well, the good news is anywhere! Let’s see where people commonly grow their plants indoors.

Basement Grow Room

Underground basements, I can’t think of a more suited space for growing cannabis indoors. These well-concealed spaces usually have no windows and tend to maintain an even temperature all year round. Thus, they’re super easy to automatically regulate. Also, basements are objectively large spaces where you’ll be able to grow a heavy crop.

Garage Grow Room

If you don’t use it to store your car, then your garage is probably a near-to-useless space packed with old and random items, thus a perfect growing space. However, garages usually are not as well insulated as basements. So you can either use it to place a large grow tent or just turn it into a grow room by blacking out windows and covering any gaps in it.

Attic Grow Room

Ghosts don’t scare you anymore, right? Well, then you can put that attic to good use. Attics are one of the safest places to grow cannabis. First, because there are few chances somebody goes up to snoop around. Second, attics tend to be completely blacked out and won’t leak any light. Although you’ll probably need to install some outlets and get some fans up there to keep the room cool -that is if you’re not using LED lights.

Closets and Your Imagination

Now, you live in a tiny apartment. That’s fine. You can use a closet. Using the micro-growing principle, you can grow compact plants in closets, broom cupboards, or boxes and still achieve excellent yields.

The limit is your imagination. Think of that old freezer that’s been sitting broken in a corner for two years. You’re right, as long as you give the plants what they need, you can turn any available space into a growing space.

How to Prepare your Space for Indoor Grow

LED lights for grow room

As we have seen, we can use various settings to grow cannabis inside. Whatever your dedicated space is, you’ll need to make arrangements in such a way you’re able to monitor temperature, humidity, light intensity, and airflow. Let’s see what tools and parameters you’ll need to consider when preparing your indoor grow space.


Temperature requirements may vary from one cannabis strain to the other. Generally speaking, you need to ensure the temperature remains in a range from 70-85°F (20-30°C) when lights are on and 58-70°F (14-21°C) when lights are off. Remember that your plants will need a different temperature according to their growth phase. Now, you need to consider which cannabis variety you’re growing. Indicas, for example, prefer to fall in the colder side of the mentioned temp range, while sativas are much more tolerant of high temperatures.


Humidity and temperature are closely related to one another. When talking about parameters for indoor grow, we refer to relative humidity. In short, relative humidity is the amount of water vapor in the air, relative to the total amount of water vapor the air can hold at that specific temperature.

And why do you care about this? Well, because temperature and humidity affect each other. Warm air holds more water vapor, increasing the relative humidity. So, you need to carefully dial both parameters and be on the lookout to have them well synched.


Airflow also relates closely to temperature and humidity levels. Therefore, you need to keep the air flowing inside your grow room or tent. Stagnant air is a serious issue for indoor cannabis growers, as this can drive up the temp and relative humidity. In turn, high temperatures and humidity can attract pests and mold.


Finally, lighting. All plants need light exposure to survive. During photosynthesis, plants will convert light energy into chemical energy, allowing them to grow strong and healthy. Indoor cannabis growers usually deploy the grow lights available in the market to simulate natural sunlight. Bear in mind the requirements for light and dark hours vary from one growth phase to another. For the vegetative stage, the ratio is usually 18 hours of light and 6 hours of dark.

Growing Cannabis Indoors: Tools and Regulation Basics

How can you measure temperature and humidity? How do you regulate these parameters? What type of grow lights should you use? Easy, I’ll leave you here the basics.

Measuring Tools

  • Thermometer: just a basic thermometer will do the trick to measure how warm or cool your grow room environment is.
  • Hygrometer: this device will measure the amount of water vapor in the air.

You can get digital hygrometers from Amazon.

Regulating Temperature

You can regulate the temperature by manipulating these factors:

  • Airflow: Sometimes, just opening your growing chamber can help remove warm air and bring in cool air. You can also use fans and ducting to set up a consistent airflow system.
  • ACs: if you live somewhere too hot and fans don’t seem to be enough, maybe it’s time for the super ACs to enter the game.
  • Heaters: On the other hand, maybe you live in an area where your garden really needs some warm air, especially when lights are off.
  • Lights: You can manipulate temperature by changing or choosing hot or cool lights.

Regulating Humidity

  • Dehumidifiers: these devices reduce water vapor from the air but will also increase the temperature, so be careful when using them.
  • Humidifiers: On the other hand, this device can increase moisture levels if it’s too dry in your grow space.
  • Water: or you can just mist your plants with a spray bottle to bring up the moisture levels.

Choosing the Grow Lights

When choosing the grow light, you need to consider several factors, such as your budget, your harvests around the year, the space in your grow tent or closet, and if you need hot or cold lights better. Depending on your needs and budget, the price may range from $100 to $2000. These are the most popular marijuana grow light types in the market:

  • HIDs (high-intensity discharge): this term also includes MH (Metal halide) and HPS (High-pressure sodium) bulbs. They’re usually inexpensive to buy, but the electricity bill will eventually come to bite you in the rear side.
  • CFLs (compact fluorescent lamps): also known as T5s among cannabis growers. These are cheap, don’t put off much heat, and will treat your energy bill nicer.
  • LEDs (light-emitting diodes): compared to the others, these are rather new to the weed-growing world. However, they’re catching up quickly because, even if they’re more expensive, they’re far more efficient and kinder to the environment and your wallet in the long run. There are high-end LEDs that will even allow you to change the spectrum for each growth phase.

Cannabis Cultivation Basics

If you have made it through, great. That means you’re a force to be reckoned with, and you have your grow tent/creepy attic ready for action. Now that you understand the basics for cannabis indoor growing let’s see what else we need to get started.

Choosing the Growing Medium

Your plants will need a medium to grow in. Basically, you can choose from two types of cultivation: soil and hydroponics.

Hydroponics is a cannabis growing method without soil. In this scenario, plant roots are suspended in water, making it easier for them to access the nutrients. However, hydroponics systems are an advanced form of cultivation and thus are not very suitable for beginners. Also, soil cultivation indoors is much easier and cheaper than hydroponics.

As for soil cultivation, you’ll find there are countless options out there. You can either purchase a “super soil mix”, which is a substrate blend that comes with the nutrients your plants will need throughout most of their growth stages. Or you can just prepare your own soil by getting the main body of a soil and adding amendments like perlite, worm casting, peat moss, fish meal, compost, and others.

Alternatively, you can use a regular soil mix and supplement your plants with liquid or solid nutrients.

Choosing the Strain

Well, telling you which strain to choose is pretty much like telling you which ice cream flavor to order. There are so many cannabis strains out there now that prohibitions are beginning to be shelved in history. And everyday breeders put their best efforts into refining and creating new varieties.

However, cannabis experts always recommend beginners start with indica-dominant strains. Indicas tend to flower faster, they’re smaller, and you can still get fantastic yields from them. Sativas are no less spectacular, although they take longer to flower, and their height might be intimidating for first-timers.

Anyhow, here are three of our favorite strains to grow indoors:

  • Bruce Banner: this is a sativa-dominant, high-yielder strain. It’s easy for rookie growers but brings a hefty, euphoric stone punch.
  • OG Kush: an indica-dominant strain that produces a decent yield and has a high level of THC.
  • Vanilla Frosting: this strain also leans toward indica. It’s great for indoors and all levels of experience. And yes, it has a creamy vanilla flavor that makes it even better.

Nutrient Requirements

Last but not least, don’t forget your plants will need nutrients. Feeding the right amount is somewhat relative. It depends on the growing medium you choose and if this medium is already packed with the necessary nutrients.

Whatever is the case, be sure to know this. Same as you need protein, carbs, and fats in your daily diet, plants will need nitrogen (N), phosphorous (P), and potassium (K). These macronutrients will help your marijuana plants grow stronger roots and leaves and thrive into their flowering stage.

Furthermore, same as you need vitamins and minerals, your plants will also need micronutrients like zinc (Zn), boron (B), iron (Fe), and manganese (Mn). Even if in minimal amounts compared with macronutrients, these will play a crucial role in various biochemical processes throughout the growth stages. Nutrient providers always include guidelines and feeding schedules to inform you about the proper nutrient ratios in each growth phase.

In a nutshell, ensure your plants are receiving their nutrients, whether it’s in a solid or liquid state or directly mixed within the soil of your choice.

A Walkthrough from Seedling to Flowering

Now that you have your grow space, you have chosen your growing medium, and the cannabis strain has come to your door, I’ll walk you through the cannabis life cycle.

growing cannabis indoors


The life cycle starts by germinating your cannabis seeds. A healthy seed must be hard and dry and have a brownish color with some stripes. If you feel it’s kind of soft when you touch it, or it looks white, then it’s probably an undeveloped seed that won’t produce a healthy plant.

Each seasoned grower might have their own germination methods. This is one of the most popular ones. Place your cannabis on a paper towel inside a plastic container. Spray the paper towel with warm water and put the lid on. Now place your container in a warm place and leave it there.

This container must always remain dark, warm, and humid. You can’t let the napkin dry. Remove the lid every few hours and spray it with water. It needs to be moist but not soaking wet. Once the seed opens up and starts showing the first white tap root, you are ready to start the germinated seed in the growing medium you chose.

The seed can take from 12-72 hours (in optimal conditions) to a few days to germinate.

Best Temperature: 77°F (25°C)

Best Relative Humidity: 70-90%


Once you have taken your germinated seeds to the growing medium, the plant will unfold from the protective case of the seed. You will see two rounded leaves, called cotyledons, emerge.

Then the stalk will continue to rise, you’ll be able to see the first fan leave, and you will probably wipe out a tear of happiness, but don’t count your joints before they hatch. Now you have a very fragile seedling that needs to be protected like a newborn baby.

Make sure you’re giving them plenty of light, about 18 hours of artificial light indoors. Don’t overwater. In this stage, their tiny roots are starting to develop. Instead, your plants will prefer to have a more humid environment. The seedling stage lasts between 2 and 3 weeks.

Best Temperature: 75-85°F (24-29°)

Best Relative Humidity: 70%


Once your seedling starts developing new fan leaves with full blades, your plant enters the vegetative stage. This phase is where the growth truly takes off, and the plant starts developing solid roots and leaves.

In this stage, your plants are like teenagers. Their nutrient requirements increase for them to be able to thrive. Feed them more nutrients, making sure you’re especially increasing nitrogen amounts. Also, don’t forget to increase the watering. When the plants are younger, they need you to water closer to the stalk. However, now you can start watering at a larger distance from the stem. Their roots are expanding and absorbing water more efficiently; thus, they won’t need a very moisture environment.

The vegetative stage is also the right time to start topping: cutting off the far end of the stalk to force the plant to strengthen the other branches and get bushier. This stage lasts between 3 and 16 weeks.

Best Temperature: 70-85°F (21-29°C)

Best Relative Humidity: 40-60%

Flowering Stage

Once your plants develop resinous buds, you will know they’re past the vegetative stage and ready to enter their flowering. When grown outdoors, cannabis plants will naturally transition into the flowering stage when they start receiving less light exposure as the summer makes way for fall.

However, indoor growers need to force their plants to flower. Once they’re ready for flowering, you will dial down the light exposure from 18 to 12 hours. There are three sub-stages during the flowering, which lasts between 8 and 11 weeks.

  • Initial Flowering (week 1-3): Your plants will continue to grow, experiencing kind of a stretch. Here you’ll notice your female plants growing pre-flowers, which will look like white hairs and later turn into buds.
  • Mid-flowering (week 4-5): The plants will stop growing, and their buds will start getting bigger and fatter.
  • Late flowering (week 6 and on): You’ll notice your plants feel stickier because the trichome density has increased significantly. The pistils’ color will tell you when it’s time to harvest.

Flowering is a good time to feed more phosphorous to your plants as this will help them with bud production. It’s also the time to lower the temperature according to the strain you’re growing.

Best Temperature: 65-80°F (18-26°)

Best Relative Humidity: 40-50%

Flushing and Harvesting

Flushing is a crucial part of the growing cycle. It’s basically cutting off all nutrients and giving only pH-adjusted water to your plants. When you flush, your plants will have to use up any remaining nutrients, resulting in higher quality and tasting smoke.

You should start flushing 1 or 2 weeks before harvesting. Once trichomes begin to form a cloudy white-colored layer, you’ll know it’s time to flush away all the buildup from the roots and soil.

Finally, as you flush, keep a close eye on trichomes and the stigma, those hair-like threads that cover buds. Trichomes will turn from clear to opaque and finally reach an amber color. The stigma strands will turn from white to orange and will start looking curlier. Congrats, your plants are ready to harvest!

best autoflower nutrients for each stage
Play Video about best autoflower nutrients for each stage

A Final Note

Growing marijuana indoors is one of the greatest experiences for cannabis enthusiasts. As you can see, we had no need of a green thumb to turn that little seed into a spectacular and bushy plant. As long as you put the effort and love needed, you have guaranteed an excellent yield and a nice trip.

As a final note, be mindful of sterilization. Always. Across all stages. A successful grow comes hand in hand with cleanliness. Spend quality time with your plants, watching their progress, and be observant of any signal your plants may be underfed or overfed. Putting that extra love is the secret sauce to achieving a great batch. Hopefully, this guide helps you find north about your journey as a newbie cannabis grower. Happy growing!