How to Grow Cannabis Indoors: Beginner’s Guide
[The information in this article has under no circumstances been created for – or is intended to be used for – illegal purposes. Growing/cultivating cannabis is illegal in many U.S. states. We, therefore, advise that all readers become familiar with current laws and regulations in their region before they learn how to grow cannabis indoors].
As a potential first-time grower, getting started is the biggest roadblock you’ll likely face. First, you have to find the right place to cultivate and obtain the proper growing equipment. Then, you need to buy cannabis seeds and spend a lot of time checking and maintaining your crop.
You must also operate within the boundaries of the law before getting started. Growing marijuana remains illegal in many U.S. states. Make sure home cultivation is allowed where you live before proceeding. Assuming you are legally able to continue, keep reading our detailed guide to growing cannabis indoors.
Step 1: Choose the Perfect Cannabis Grow Room
You don’t need a particularly large growing/cultivating space. A typical grow room for a small-scale grower is a small tent, cabinet, or designated area in a spare room, even an unused corner of the house is sufficient! Here are a few helpful tips to get started.
1 – Begin Growing from a Small Plot & Adjust as Necessary
By “small,” I mean nothing more than a few plants at most. You can start with just one or two plants. There’s an inevitable learning curve involved with growing weed indoors and you’re bound to make some mistakes.
It shouldn’t take long to get the hang of things and start producing some beautiful, flowering cannabis plants, but you’ll need to make room as your plants grow. From the first signs of flowering, you can expect a plant to double or even triple in size by harvest time.
Make sure that you have enough space to work in!
2 – A Clean Space is One of the Most Important Things to Remember
Make sure your cultivating space is sanitized and clean. There’s an inherent risk posed by pests and contaminants. A messy space invites pathogens, harmful bacteria, and mold. A good idea is to plan a bi-weekly cleaning routine and stick to it.
Marijuana plants are “bioaccumulators,” which means they “suck up” everything around them (both in the air and the soil). Make sure the area surrounding the plants is clean enough to keep potential contaminants out.
3 – Keep Your Grow Space as “Light-Sealed” as Possible
Light is essential for the growing process. Your plants receive direct light the majority of the time. Be direct here: eg. plants need 12 hours of continuous, uninterrupted darkness to flower and eventually produce buds.
Like most living things, cannabis plants need their “rest time.” If light from a surrounding source is seeping in during dark hours, the (bud-producing) females could get confused and develop hermaphroditic characteristics.
A hermaphrodite cannabis plant will produce flower that’s full of seeds, ruining your chances of a decent yield of smokable buds.
4 – Successful Indoor Growing Requires the Following Features
- Choose a secure place safe away from animal and human invaders, somewhere you can monitor them regularly.
- Temperature and humidity need to be carefully and conscientiously managed.
- Make sure your spot is safe and easily accessible at any time, day or night.
Step 2: Choose (and Use) Your Cannabis Grow Lights
The light source you use in your grow room plays a significant role in determining the quality of the plants. I recommend spending a large portion of your budget on a good lighting setup. It is worth it in the end, particularly if you plan on growing long term.
Here’s a basic rundown of the most popular types of cannabis grow lights used today.
LED grow lights
If cost isn’t a consideration, LED (light-emitting diode) lighting is the preferred option for most marijuana growers. These are highly efficient light fixtures for indoor growing. They use less energy and create very little heat. LEDs produce wavelengths across the light spectrum, so they can be used for both the vegetative and flowering cycles.
The drawback is they can cost 3-5 times more than a decent HID setup! If you’re serious about getting into growing and have money to spend, however, give serious consideration to LEDs. But do your homework to avoid ‘scam’ LEDs online.
Induction grow lights
Induction lamps are an odd choice for indoor growers. However, some companies have recently adapted them for the cannabis industry. They can potentially represent decent value in terms of cost and efficiency.
Nikola Tesla invented the process of generating heat from magnetic induction in the 19th century. These types of lamps produce bright light with little heat compared to HID setups.
HID grow lights
The most commonly used lights for DIY-style growing are probably HID (high-intensity discharge) grow lights. They typically represent the best overall value in terms of cost, efficiency, and ease-of-operation.
The main drawback is that they require numerous accessories to run correctly. As a consequence, the overall cost can ramp up pretty quickly, depending on how much you’re willing to splurge.
For example, most growers use one of two main types of HID lamps/bulbs depending on the developmental stage. Metal halide (MH) bulbs are best during vegetative growth. High-Pressure Sodium (HPS) is the preferred option for the mature flowering stage. If you can only afford one, choose HPS as they are much better for flowering and are more efficient on a ‘watt-to-light’ scale.
HID lights produce a substantial amount of heat. Therefore, proper use of air circulation and conditioning becomes vital. Some growers choose air-cooled fixtures to mechanically remove heat.
Fluorescent grow lights
Fluorescent lights are generally much cheaper and easier to use than the other options. They represent an excellent option for propagation of young plants or those with extremely low yield expectation. And remember: watts = grams. Low wattage will not prevent you from growing potent little flowers. They also don’t require a connection to an external ventilation system. Fluorescent lights are far less powerful than the other options. However, for novice DIY growers with a single plant or two and little space, they might be your best bet.
Step 3: Fresh Air is the Lifeblood of Healthy Cannabis Plants
Make sure you have consistent airflow across your entire plot. Depending on the size of your grow room, you can achieve this easily. Utilize several types of fans, including oscillating wall mount, stand fans, and box fans. Place them strategically to create good air flow throughout the space.
Since warmer air rises, mount your exhaust fan(s) high so they can suck out hot, stagnant air. On the flip side, your intake fan should be mounted low so it can provide a good supply of cool, CO2-filled fresh air. This technique allows for a constant supply of fresh air for your plants. It also helps keep temperatures to a manageable level.
Most cannabis strains prefer an upper-temperature range between 75- and 85-degrees Fahrenheit. When the lights are off, keep room temperature between 55 and 75 degrees. Indica strains tend to prefer the cooler end of the range.
Step 4: Develop a Control System and Monitor the Growing Process
The next step is a self-monitoring system to control it all. We assume you can’t spend 24 hours a day in your grow space! You need a 24-hour timer and an adjustable thermostat. The latter allows you to set your exhaust fan to switch on once temperatures go above a certain degree. The result is a relatively stable temperature range and humidity level while saving energy and money.
The 24-hour timer is just as important. When the marijuana plants are in vegetative growth, you need the light supply on for around 16-24 hours per day. Once they mature and reach the flowering stage, your plants need 12 hours light and 12 hours dark.
We also recommend investing in a pH meter to check on the quality of your water and soil regularly. If you’re growing in soil, try to keep the pH between 6 and 7, with the sweet spot being 6.2-6.5. If you’re growing hydroponically, 5.5 to 6.5 is an appropriate range with the sweet spot of 5.8-6.0.
EDITOR’S CHOICE – Homegrown CannabisCo
Homegrown CannabisCo are the masters when it comes to seeds. Offering a massive variety of cannabis seeds that are well categorized, not only does this company create a resource for superb quality options including feminized seeds, it also provides extensive growing information for those looking for some support along their journey.
Step 5: Be an Artist! [And Choose a Cannabis “Grow Medium”…]
When cultivating cannabis indoors, there are two viable options: Growing in traditional soil or a hydroponic tray. Soil is typically recommended if you’re growing indoors for the first time. It’s cheaper, more straightforward, and more forgiving than an advanced hydroponic system. Let’s take a closer look at each of the two options.
Soil vs. Soilless Growing
Soil is less expensive, easier, and offers a higher margin of error. However, you need to carefully select the soil you use because quality can vary enormously.
General potting soil doesn’t work very well. You want a high-grade horticultural potting mix, which is light and airy. Some mixes come “charged” with a small amount of nutrients to get you through the first few weeks. However, these will need regular fertilizing later.
Other mixes are “neutral,” without any nutrients present. These mixes need appropriate amounts of fertilizer right from the start. Amendments to soil ingredients include compost teas and mycorrhizae bacteria, as well as other organic compost nutrients.
Another idea is “all-in-one” automated hydroponic setups, which may help you experience faster growth and more abundant yields. This is only the case if everything is done correctly – all the time, every time (unlike soil which has natural buffers to give you some wiggle room).
A hydroponic system delivers all necessary mineral salt nutrients to plants in water. If you want to choose hydroponic over traditional soil, there are several types which are straightforward and fairly easy to understand. These include Ebb and Flow, Flood and drain and DWC or Deep Water Culture.
Step 6: Choose a “Canna-tainer” (Container) to Grow Your Cannabis In
It’s very important to grow your cannabis plants to a size suitable to your space and likewise to the container you choose. You will need to transplant every time your plants double to triple their size. Small cups or 4-6” pots are good for starts.
Think about how big you ultimately want to grow your plants when deciding on pot size for their final home. I suggest one-gallon of soil for every foot tall you intend to grow them. Regardless, plants don’t like waterlogged conditions so perforate the bottom of the bucket so the water can drain as needed.
There are some outstanding pre-filled soil kits specially designed for increased airflow. Keep these in mind when deciding what to grow your first cannabis plants in.
Step 7: Show Your Cannabis Plants Some Love (By Giving Them Lots of Nutrients)
Ensuring your plants get the right nutrients is probably second only to lighting in terms of importance. Proper nutrient selection and application are among the most critical factors in growing premium-grade cannabis. While weed is resilient, growing it in sub-optimal conditions means you will miss out on yield and potency.
Whether you’re using an organic soil mix or growing hydroponically, your cannabis plants need the “super seven” macronutrients. In no particular order, these are:
- Nitrogen (N)
- Phosphorous (P)
- Potassium (K)
- Calcium (Ca
- Magnesium (Mg)
- Iron (Fe)
- Copper (Cu)
You can get these macronutrients pre-packaged in liquid or powder form (if you’re using an un-supplemented soil mix). However, a lot of organic “super soils” already contain them in sufficient amounts.
Lastly, some strains indeed require more calcium than others to produce robust, healthy nugs. Perform a little research on the particular strain you are growing. This process enables you to become more familiar with the kind of “food” it needs and prefers the most.
Step 8: Cannabis Plants LOVE Water!
A common assumption amongst rookie plant growers is that the more you water, the better.
While this is true to an extent, there is such a thing as “too much water.” Overwatering your indoor cannabis plants can prove detrimental to their productivity, and potentially stunt or kill them!
The frequency of watering and the amount you give is determined by a few obvious things. These include the size of the plant, the stage of development, and the rate of photosynthesis (how fast it’s growing). However, there’s no exact science when deciding how much water to give and how often.
Make sure there are holes drilled into your growing container so the water can drain out. When watering, try, and only moisten the soil rather than saturating it. This allows you to fully saturate the pot without overwatering. Try not to water until they’re almost dry. This is called cycling.
Lastly, consider using an RO filter as excess levels of chlorine and unfiltered minerals could harm the plants. You may want to choose a distilled option or at least filter it before adding it to your soil. Mineral-laden tap water can cause unwanted build-up in the cannabis root systems, which can lead to detrimental root disease.
Step 9: Set Time to Care For Your Plant (Every Single Day!)
DIY indoor growers are unable to perform a 24/7 watch over their plants. However, you can provide adequate care by setting aside a few minutes a day. Routine checks, such as ensuring things like temperature, humidity, pH, and water levels are correct, are essential.
Also, watch out for male plants in your crop. If you wish to grow high-THC buds, the only thing you want in your crop is female plants. If you have a male in your crop, REMOVE IT. Once it reaches maturity and its pollen sacs burst, it fertilizes the females. At this point, they’ll start developing seeds rather than growing buds. While the plants won’t die, their ability to yield buds is ruined.
If you don’t know how to tell a male cannabis plant from a female, we’ve got a great article on the topic.
If you’re growing from seed, you need to wait until the flowering stage. After a week of nighttime photoperiod, the plants will start reaching maturity and will develop reproductive parts at the nodes.
This is when you can extract the male plants and eliminate them. Male plants will have what look like little clusters of bananas; these are the pollen sacs. Female plants will have sharper early-stage calyxes with white hairs (pistils). Those growing from female clones or pre-purchased feminized seeds should have no concerns about male plants.
Step 10: Cut Your Cannabis Plants Down — Carefully!
The final step involves harvesting your plants. Once you get used to the process, you’ll find it more enjoyable than tedious.
The first step is to cut off the big water leaves, otherwise known as the fan leaves. They have minimal THC in them and are generally removed. You’ll notice a visible difference between the long, green fan leaves and the smaller sugar leaves. The latter is covered in resinous glands (trichomes).
Some people like to grind the sugar leaves and use them. However, it is all about the clean, leafless nugs if the goal is to fully enjoy an intoxicating high. You can use the sugar leaves to make cannabutter, however. After trimming, you should hang the buds up to dry. After 7-10 days, you can place them in airtight containers to cure. The more patient you are, the better the buds will taste. They are also more potent!
Final Thoughts on Growing Cannabis Indoors
Harvesting hemp and cannabis is a lovely experience. It is one we recommend to any weed lover who has a passion for all aspects of the plant. You learn so much about cannabis and botany/biology in general. Most growers believe they learn something new with every harvest.
There’s no doubt a bit of a learning curve involved. You’ll make your fair share of mistakes. However, trust us when we say it’s all worth it in the end.
Enjoy, and more than anything else; remember to HAVE FUN!
EDITOR’S CHOICE – Homegrown CannabisCo
Homegrown CannabisCo are the masters when it comes to seeds. Offering a massive variety of cannabis seeds that are well categorized, not only does this company create a resource for superb quality options including feminized seeds, it also provides extensive growing information for those looking for some support along their journey.
How to grow weed indoors
Growing weed indoors is great because you can grow it any time of year and you’ll have complete control over the plant and what you put into it. Live in an apartment or a small house? Don’t worry, you can grow weed practically anywhere, even if you don’t have a backyard or a lot of extra space.
Benefits of growing weed indoors
Although it’s more resource-intensive than growing outdoors and you will likely have to spend more money on utilities to power equipment, you can control every aspect of your grow environment and what you put in your plant, allowing you to dial in your setup to grow some primo weed.
Unlike outdoor growing, you aren’t tied to the sun and the seasons. You will be providing the entire environment the plants need to grow, including the grow medium—soil, rockwool, etc.—and regulating the amount of water and nutrients they receive, as well as controlling temperature, humidity, and more for them.
You can let your plants get as big as you want, and can control when they flower and when you harvest, and you can start another batch right away or whenever you want. You can grow any time of year, even straight through winter or summer, and you’ll get consistent crops each time.
Privacy and security
Even in legal states, you may want to conceal your crop from judgmental neighbors and definitely from potential thieves. Growing indoors allows you to grow discreetly behind a locked door.
How to set up an indoor grow room
Below is a list of things to consider and equipment you will need to purchase to get started growing marijuana indoors.
You’ll need a dedicated space for your marijuana plants—you won’t be able to move them around. Ideally, the space is next to a window so you can vent air from the grow space outside. Growing weed plants smell! Especially when flowering kicks in, you’ll want to redirect air so your house doesn’t reek of weed.
A lot of people these days buy grow tents for their weed, but they aren’t necessary. You can grow in a closet, tent, cabinet, spare room, or a corner in an unfinished basement. Just keep in mind that you’ll need to tailor your equipment (and plants) to fit the space.
It’s a good idea to start small—the smaller the grow, the less expensive it is to set up. Newbie mistakes will be less costly if you only have a handful of plants. Additionally, most state laws only allow for growing six plants, but some allow up to 12.
When designing your space, you’ll need to take into account room for your plants, as well as space for lights, fans, ducting, and other equipment. You’ll also need space to work on the plants. Cannabis plants can double in size in the early stages of flowering, so make sure you have adequate head space!
Every space is different and there will be a learning curve to growing in yours.
Cannabis, like all plants, prefers certain environmental conditions in order to thrive. Temperature, humidity, light intensity, and airflow are all factors that will need to be monitored and regulated in order to keep cannabis healthy through its different phases.
Although you’ll be controlling the climate inside the grow space, climate outside the grow space will affect your plants. If the environment outside your grow space is very warm or humid, you’ll have issues controlling your grow space. Choose a cool, dry area with ready access to fresh air from outside.
If you’re growing in a cold, wet basement, you might have to run a dehumidifier or heater to stabilize the environment. Conversely, if your space is too hot, you might need to add extra fans or an AC to cool the plants down.
One trick to avoid hot temps is to have the grow lights on during the evening, when it’s cooler outside, and leave the lights off during the day when it’s hot. This may help bring down the temps, but you’ll only be able to work on the plants at nighttime when the lights are on.
Weed plants need different amounts of light during their vegetative and flowering stages. You don’t have to worry about this in an outdoor setting—the sun and the season dictate this—but when growing indoors, you will be controlling it.
Plants need 18 hours of light a day when in the vegetative stage and 12 hours a day when flowering. The reduction in light from 18 to 12 hours a day is what triggers the flowering cycle—when weed plants start to grow buds.
Because the amount of light a plant receives is so important, you’ll need to make your indoor grow space light-tight. Light leaks during dark periods will confuse your plants and can cause them to produce male flowers or revert to a different stage.
Different lights produce different colors of light. Here’s a brief rundown of the most popular types of cannabis grow lights used for indoor growing.
HID (high-intensity discharge) lights are the industry standard, widely used for their combination of output, efficiency, and value. They cost a bit more than incandescent or fluorescent fixtures, but produce far more light per unit of electricity used. Conversely, they are not as efficient as LED lighting, but they cost much less.
The two main types of HID lamp used for growing are:
- Metal halide (MH) produces light that is blueish-white and is generally used during vegetative growth.
- High pressure sodium (HPS) produces light that is more on the red-orange end of the spectrum and is used during the flowering stage.
In addition to bulbs, HID lighting setups require a ballast and hood/reflector for each light. Some ballasts are designed for use with either MH or HPS lamps, while many newer designs will run both.
If you can’t afford both MH and HPS bulbs, start with HPS as they deliver more light per watt. Magnetic ballasts are cheaper than digital ballasts, but run hotter, are less efficient, and harder on your bulbs. Digital ballasts are generally a better option, but are more expensive. Beware of cheap digital ballasts, as they are often not well shielded and can create electromagnetic interference that will affect radio and WiFi signals.
Unless you’re growing in a large, open space with a lot of ventilation, you’ll need air-cooled reflector hoods to mount your lamps in, as HID bulbs produce a lot of heat. This requires ducting and exhaust fans, which will increase your initial cost but make controlling temperature in your grow room much easier.
Fluorescent grow lights
Fluorescent light fixtures, particularly those using high-output T5 bulbs, are quite popular with small-scale cannabis growers because:
- They tend to be cheaper to set up, as reflector, ballast, and bulbs are included in a single package.
- They don’t require a cooling system since they don’t generate nearly the amount of heat that HID setups do.
The main drawback is fluorescent lights are less efficient, generating about 20-30% less light per watt of electricity used; space is another concern, as it would require approximately 19 four-foot long T5 bulbs to equal the output of a single 600 watt HPS bulb.
LED grow lights
Light emitting diode (LED) technology has been around for a while, and they are getting more efficient all the time. The main drawback to LED grow lights is their cost: well-designed fixtures can cost 10 times what a comparable HID setup would.
But the benefits are great: LEDs last much longer, use far less electricity, create less heat, and the best designs generate a fuller spectrum of light, which can get bigger yields and better quality.
Check out our buying guide on indoor lights for more info.
Plants need fresh air to thrive and carbon dioxide (CO2) is essential to the process of photosynthesis. This means you will need a steady stream of air flowing through your grow room, which will allow you to move hot air out of the space and bring cool air in.
This is easily achieved by placing an exhaust fan near the top of the space to suck out warm air—warm air rises—and adding a port or passive fan on the opposite side of the space near the floor to bring in cool air. A complete air exchange throughout the entire grow space should occur once every minute or so.
Without proper airflow, a grow space can experience rapid changes in humidity or develop pockets of CO2 depletion, neither of which are good for plant growth. CO2 depletion can lead to nutrient lockout, and areas of high humidity are prone to pest infestation, mold, or mildew.
It’s also a good idea to have oscillating fans to provide a constant breeze in your grow room as it will strengthen your plants’ stems, making them stronger and healthier.
Setting up fans
For small spaces or tents, clip-on fans can be attached to structures like walls, corners, or support beams. For larger grow rooms, use medium-sized oscillating fans or big floor models.
Fans should be positioned to provide direct, even airflow throughout the garden. This typically involves using multiple fans that work together or fans that have oscillation capabilities.
There should be a comfortable airflow both above and below the canopy, and fans shouldn’t blow air directly onto plants—this can cause wind burn, which makes leaves recede into a claw-like deformation.
Dehumidifiers and ACs
If your space is too humid, you may need to invest in a dehumidifier—also known as “dehueys.” However, keep in mind that while dehueys will reduce humidity, they typically increase temperature—you may need more fans or an AC when adding a dehumidifier.
Getting the right climate for your plants can be a delicate balance involving multiple pieces of equipment and also lots of electricity. This is part of what makes growing weed indoors more expensive than growing outdoors.
Fans are a must in a grow space to move air around, so buy some of those before an AC unit. If you find that fans aren’t bringing down the temperature enough, then you may want to invest in an AC.
You will definitely want to invest in a timer for your lights. Because the amount of light a plant receives dictates its vegetative or flowering stage, it’s important to give it a consistent amount of light every day, and that’s done with a timer. It’s a good idea to check your timer at least once a week to make sure it’s working properly.
You can also use a timer for your fans, but a thermostat is better—you can set it to a specific temperature, and the fans will turn on when it’s too hot and turn off when it’s too cold.
Most dehumidifiers and ACs have built-in thermostats, but if they don’t, you’ll want to buy an external one.
For growers who have a little extra money to spend and want full control over their indoor garden, environmental controllers will allow you to automate the process. These devices are essential for if you’re away from the garden for a long period of time.
You can connect a controller to fans, dehumidifiers, humidifiers, heaters, or air conditioners, and set thresholds whereby each device will power on and off based on your ideal environmental settings. Some units run autonomously, making changes based on set parameters, while others allow you to control each element via an app on a phone, tablet, or computer.
Regulating temperature and humidity in your indoor grow space
You’ll need to ensure that temperatures remain within a comfortable range for your plants, between 70-85°F when lights are on and between 58-70°F when off. Some varieties of cannabis—generally indicas—prefer the colder side of the range, while others—typically sativas—are more tolerant of high temperatures.
For the most part, weed prefers these temps at each growth stage for optimal health:
- Seedlings/clones: 75-85°F; ~70% relative humidity
- Vegetative growth: 70-85°F; 40-60% relative humidity
- Flowering: 65-80°F; 40-50% relative humidity
The two factors you need to control to dial in the environment are temperature and humidity.
Inevitably, there will be fluctuations of temperature and humidity in your cannabis garden. These fluctuations can occur both throughout a grow space as well as within pockets inside a given room. They can also occur at different points within a given day or throughout a season as conditions change in the environment outside your grow space.
It can be tricky getting the right balance of temperature and humidity because they affect each other—turning up your dehumidifier will lower the humidity of your grow space, but it will also increase the temperature of the area. This in turn may require you to turn on an AC unit—everything’s connected!
Tools to measure temperature and humidity
Equip yourself with these cheap and easy-to-use tools to take measurements in your indoor cannabis setup:
- Thermometer: A basic one will allow you to measure how warm or cool the environment is inside your garden.
- Hygrometer: This measures humidity, or more specifically, water vapor content in the air.
- Infrared thermometer, or IR thermometer (optional): IR thermometers use a detection device called a thermopile to measure surface temperatures. Although not necessary, these are helpful in finding out leaf temperatures, which will give you an extra layer of knowledge on how to properly regulate environmental conditions.
Controlling temperature in your indoor grow room or cannabis garden can be achieved by manipulating these factors:
- Lights: Different grow lights will give off different heat signatures. Hot lights such MH, HPS, and fluorescents produce much more heat than LEDs. Also, lights can be raised or lowered to change temperature at the canopy level.
- Airflow: You can remove warm air (up high) out of the garden and bring in fresh cool air (down low) with fans and ducting. Fans can also help exchange air throughout your canopy, cooling leaves in the process.
- ACs: You may need to bring in an air conditioner to rapidly cool the overall temperature of your grow space if it’s too hot and fans aren’t enough.
- Heaters: Some gardens may require warm air, especially during times when lights are off and not generating heat.
Humidity is the amount of water vapor in the air. Here are some ways to control it in your marijuana grow room:
- Dehumidifiers: Dehueys remove moisture from the air but also increase temperature.
- Airflow: As with regulating temperature, regulating airflow will allow you to move moisture in and out of your grow space and control humidity—simply opening up a space, i.e., opening the door to your grow room or tent, can bring down humidity.
- Humidifiers: A humidifier can add water vapor to a grow space and increases moisture levels if it’s too dry.
- Water: In the absence of a humidifier, you can mist plants with a spray bottle to create extra moisture.
Soil and other media for growing weed indoors
There are many different media to choose from, including good ol’ fashioned pots full of soil, rockwool cubes, a hydroponic tray, and more.
Soil is the most traditional medium for growing marijuana indoors, as well as the most forgiving, making it a good choice for first-time growers. Any high-quality potting soil will work, as long as it doesn’t contain artificial extended release fertilizer—like Miracle Gro—which is unsuitable for growing good cannabis.
Good soil for cannabis relies on a healthy population of mycorrhizae and soil bacteria to facilitate the conversion of organic matter into nutrients that a plant can use. Alternately, you can use a regular soil mix and then supplement your plants with liquid nutrients.
Finding the right soil for cannabis
For most first-time gardeners, we recommend buying a quality potting soil that will provide your plants with enough nutrients to get them through most of their growth cycle without having to add many amendments or liquid nutrients. This pre-fertilized soil—often referred to as “super-soil”—that can grow cannabis plants from start to finish without any added nutrients if used correctly.
You can make this yourself by combining worm castings, bat guano, and other components with a good soil and letting it sit for a few weeks, or it can be purchased pre-made from a local nursery or grow shop.
While shopping for soil, you might be overwhelmed by the options available at your local garden store. The soil type is the basic structure of your soil. From there, look at nutrients, microorganisms, and other amendments that improve the soil. Your choices will be flooded with words like:
- Worm castings
- Bat guano
- Peat moss
- Fish meal
- Bone meal
- Glacier rock dust
- Plant food
These are just some examples of amendments commonly used in different types of soils. Heavily amended soils will have long lists that break down all organic nutrients they contain. Some companies create soils that offer a great structure with base nutrients, but allow you to fill in the gaps as you desire.
What type of container you use will depend on the grow medium, the system, and the size of your plants.
Inexpensive options include standard plastic pots or cloth bags, while some growers choose to spend more on “smart pots” or “air pots”—containers designed to enhance airflow to the plant’s root zone.
What size pot do I need?
Many growers will start plants in a one-gallon pot and then transplant up to a bigger pot as plants get bigger. A lot of growers will transplant once, from a one-gallon to a five-gallon pot, and harvest from there. If your plants get bigger, they may need a seven- or ten-gallon pot.
What to look for in a pot
Your cannabis wants a safe, healthy place for root development. Without healthy roots, your cannabis will never thrive. Roots are in charge of water retention, nutrient absorption, anchoring the plant, and they also facilitate vegetative growth.
Drainage is key, as cannabis plants can get waterlogged and develop root rot. If you repurpose containers, be sure they have holes in the bottoms and set them in trays.
For a root system to develop and thrive, they will need the following:
- Drainage: Water retention is paramount for healthy plants—without it, your cannabis will wither and die. But too much water will waterlog your plant and lead to root rot, killing roots.
- Oxygen: Plant roots require oxygen to function properly. Choose a container that facilitates enough oxygen for root development without overexposing them to the elements—containers do this though various styles of perforation.
- Nutrients: Roots require optimal conditions for nutrient absorption to occur. This includes pH balance, optimal temperatures, and nutrient availability.
- Space: Roots need plenty of space to branch out. A container that is too small will cause it to become rootbound and choke the plant.
Traditional plastic containers
Standard plastic containers are a popular option for growers operating on a budget. These pots are inexpensive and provide the essentials for your plants.
- Low overhead costs
- Solid drainage (plus it’s easy to add more holes)
- Transplanting is easy and inexpensive
- Can’t protect root systems from temperature fluctuations as well
- Lack of durability which can cause cracks and structural damage over time
- May have airflow issues depending on the grow medium
These are quickly becoming the standard. Roots in fabric pots grow to the outer edges and attempt to bypass the porous fabric wall but are cut back, allowing new growth to occur. This process, called “air pruning,” results in a denser root composition which promotes healthy growth and development.
- Promotes dense, healthy root systems
- Increased airflow to roots
- Excellent drainage
- Require more attention and maintenance because they dry out quickly. Note: You can use larger pots to help slow drying.
- Flimsy structure can make plant support challenging
Terra cotta pots offer a unique set of benefits to growers in hot climates.
- Absorb moisture and retain lower temperatures during hot days
- Heavy weight helps to anchor larger plants
- Less than optimal drainage; drilling holes into clay pots is possible but requires special tools and is labor-intensive
- Heavy weight makes it difficult to transport plants
Caring for your indoor cannabis plants
When starting with clones or seedlings, you’ll want to check your plants every day because they’re delicate and sensitive to environmental conditions. You may need to adjust temperature and humidity levels in your indoor grow space at first to hit the sweet spot for your plants.
As your indoor weed plants grow, they’ll need less attention, but you’ll still need to check up on them every 2-3 days.
Watering and nutrients
When growing weed indoors, you’ll likely have to add nutrients to your plants. You won’t need to add nutrients every time you water, but get on a schedule where you water every other time, or two on, one off.
Before watering, check the pH of your water and add pH Up or Down if needed.
If using nutrients, estimate how much water you’ll need for all of your weed plants so you can measure out and mix in the appropriate amount of nutrients.
Remember, a common mistake newbie growers make is to overwater plants.
Check out our Guide on nutrients for more info.
Check for pests, mold, or nutrient deficiencies
You’ll also want to take this time to check over your weed plants for pests, mold, or nutrient deficiencies.
Examine the tops and undersides of leaves for pests or discoloration—spider mites live on the underside of leaves—as well as stalks and branches. Also, check the soil for pests.
Make sure all equipment is on, no breakers have flipped, and everything is running smoothly. Check lights, timers, fans, dehueys, ACs, and anything else that plugs into the wall or has a battery.
Think of all the equipment in your grow space as organs in the body—if one fails, the others will have to work a lot harder for a bit, and then will fail in a matter of time.
Daily maintenance checklist for your indoor marijuana grow
- Water plants
- Check pH of water
- Measure and mix nutrients
Indoor marijuana grow timeline
The growth stages of marijuana can be broken down into four primary stages from seed to harvest:
- Germination (3-10 days)
- Seedling (2-3 weeks)
- Vegetative (3-16 weeks)
- Flowering (8-11 weeks)
Generally speaking, it takes anywhere from 10-32 weeks, or about 3-8 months, to smoke what you’ve grown. (It’ll be quicker if you start with a clone or an autoflower seed.)
That’s a big variance, but it really depends on how big you want your plants and how often you want to harvest—you can have multiple harvests of smaller plants, or less harvests of bigger plants.
For example, it takes less time to grow 3′ weed plants than 5′ plants; in the span of a year, you can maybe grow four harvests of 3′ plants, or two harvests of 5′ plants.
You’ll likely yield about the same amount of weed in both cases, but more harvests mean you’ll have fresh weed to smoke more often and have more opportunities to grow different strains. But more harvests also means more work in cleaning up the space between harvests, trimming, etc.
The biggest variability in how long a marijuana plant takes to grow will happen in the vegetative stage—after the seedling phase and before flower.
The flowering stage will always take about eight weeks—some strains take seven, some nine, some even more, it depends on the strain.
So when growing weed indoors, you can control the size of your plants by flipping them into flower whenever you think they’re big enough in the vegetative stage.
Odor control in your indoor marijuana grow
As much fun as growing marijuana indoors is, having a home that perpetually smells like fresh weed can be a serious inconvenience, if not to you than possibly your neighbors. Although weed odor from a small indoor grow in a closet is much easier to manage than a large grow with several flowering plants, both can produce pesky odors that will permeate an entire home if left unattended.
Plants in the vegetative stage maintain a low odor as they haven’t begun to produce terpenes, the plant’s aromatic compounds. As weed plants transition into the flowering phase, trichomes will start to develop and produce terpenes, causing them to smell more.
Here are some ways to mitigate odor when growing weed indoors.
Check temperature and humidity levels
The first step in odor control is making sure temperature and humidity are under control in your grow space—high temperature and humidity will perpetuate odors.
As your plants get bigger and especially when they start flowering, they’ll start to smell more. Outfitting your grow with a dehuey or AC can help bring odor down.
Make sure air is circulating through your garden
Proper air circulation will help maintain temperature and humidity, and also bring down odor. Ideally, air needs to move through a garden every few minutes, and you should create a vent to the outside. Oscillating fans, and intake and exhaust fans can move air through your garden quickly, taking odors out with them.
Odor absorbing gels may help
Odor becomes much more difficult to manage in the final six weeks of a marijuana plant’s life, when trichomes and terpene production ramps up. You can also get odor-absorbing gels, which replace weed smells with other scents. Keep in mind that odor gels don’t eliminate odors, but simply mask them.
Activated carbon filters
These come in different shapes and sizes and are a great way to get rid of odor in an indoor weed grow. Also known as “carbon scrubbers” for their ability to get contaminants out of the air, these employ activated and highly ionized carbon to attract particulates responsible for carrying odor, such as dust, hair, mold spores, and volatile organic compounds, and traps them in a filter.
Carbon filters usually work best when positioned at the highest point in your grow space, where the most heat accumulates.
Patrick Bennett and Trevor Hennings contributed to this article.