A beginner’s guide to growing marijuana indoors
Last updated on Dec 23, 2024
Created on Nov 22, 2022
Article written by
April AcernoContent Writer
Content reviewed by
Dipak HemrajMedical Cannabis Researcher
If you’ve decided to start growing your own cannabis, growing indoors is a great place to start. While outdoor growing has various benefits, indoor growing allows for more control, making it perfect for beginners.
Certain growing tips apply to both indoor and outdoor growing. However, it’s important to know the differences between the two methods and what they involve so that you can start growing healthy cannabis plants in no time.
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Benefits of indoor growing
Indoor cannabis growing has a number of benefits. While it can be costly due to the equipment needed, you have more control over the environment that your plants are growing in. You can manage the exact water, light, and nutrients they receive, as well as the temperature and humidity of the growing space. And you don’t have to deal with as many pests.
You also aren’t tied to the seasons or the weather, meaning that if you want to start in the middle of winter, you can — as long as you have the equipment needed to regulate your grow room’s light, temperature, and humidity. This means you can keep growing throughout the seasons, potentially leading to multiple harvests each year.
Finally, you have more privacy. Even if you’re legally allowed to grow weed, growing indoors keeps your harvest away from prying eyes and potential thieves.
How to set up an indoor grow room
You will need a suitable setup space for your grow room. This could be a spare room in your home, a garage, or a basement. Even a cupboard will work as long as it’s sealed appropriately so that light cannot get in.
Cannabis needs time in the dark, so you’ll have to be aware of this if you’re using an entire room to grow. If light gets into your grow area during the dark stage of the plant’s light cycle, it can stress the cannabis plants and lead to problems with growth.
Most new growers start with a small, manageable grow room of around 3 feet by 3 feet, which can hold between four and nine plants. Only one light is needed to cover a space of this size, and it’s often best to start small to understand the cannabis plant’s growth patterns before moving on to bigger projects.
Note that some states require that cannabis plants be grown out of the public’s sight. Keep that in mind when choosing where to set up your grow room.
Items needed
Indoor growing requires more equipment than outdoor growing. But having access to these items means you can control your plants’ surroundings. For example, with outdoor grows, you can’t control the weather. With indoor grows, however, you can adjust the temperature, humidity, airflow, and lighting as needed.
Some items you will need are:
- Grow tent: A special tent that’s black on the outside to prevent light from getting in and has a refractive material on the inside, which casts light in different directions. This helps you to get the most out of your lights.
- Lights: Lights of the correct wattage (power level) to help the plants grow.
- Platform: A platform to create a place for your plant pots.
- Plant pots: Pots of various sizes to store the plants.
- Extractor fan: A fan to take hot air away from the top of the grow area.
- Intake fan: A fan to pump new air into the room or grow tent.
- Carbon filters: Filters attached to your extractor fan to reduce the smell of cannabis.
- Thermometer: A thermometer to ensure you’re keeping your plants at a temperature of around 79 to 83 degrees Fahrenheit (26 and 28 degrees Celsius).
- Hygrometer: A humidity gauge to measure the level of moisture in the grow space.
- Timer: A timer to switch lights on and off when you’re not at home. Timers can also be useful for feeding in a hydroponic system, a growing technique that uses water instead of soil.
Lighting
For the vegetative stage — when the plant sprout begins to grow leaves, stems, and roots — you will want a grow light of around 100 to 125 watts.
After around four to six weeks of vegetation you should switch to a grow light of about 250 watts or above to trigger flowering.
Other things you will need for your light include:
- A ballast: This regulates and controls the supply of energy needed to power the light.
- A reflector: Reflectors surround the top of the light to direct the light downwards towards your plants
- A lamp of suitable wattage: You’ll want to keep the wattage between 250 and 400 watts for smaller grow rooms without much head room. Too high a wattage can actually lower your harvest if the room gets too hot.
- Structural materials: A heavy chain or another material strong enough to hang your lights.
There are also different types of lights filled with different gases. Here are some things to consider when choosing your cannabis grow lights:
- Halide lights: During the vegetative stage, most people choose metal halide lights as they produce more blue light.
- Sodium lights: During flowering, sodium lights are preferred as they produce more red light.
- Fluorescent lights: These can be useful for plants when they are in the seedling stage, or for propagating plants. Propagation refers to creating additional plants from your existing plants.
- LED lights: These are becoming more common as they’re more energy efficient, don’t need to warm up, and can be used throughout the growing process, but they can have a large upfront cost.
- Supplementary grow lights: Options like plasma and ceramic discharge metal halide (CDM) lights can enhance bud production, but these are not necessarily required for smaller grow rooms.
Fan placement
Plants need fresh air and carbon dioxide to grow, so it’s important to keep air moving through your grow space. This is where extractor fans and intake fans come into play.
The main purpose of an extractor fan is to remove warm air from the room. Because warm air rises, your extractor fan must be placed high up.
Your intake fan is responsible for bringing fresh air into the area. It’s placed on the opposite side of the room. Ultimately, the size and number of fans will depend on how big or small your grow space is.
In addition to fans, you may also need a dehumidifier or air conditioner unit to help control the humidity or the temperature in the room, depending on where your grow space is.
Choosing an indoor grow medium
One of the advantages of growing cannabis indoors is that you get a high degree of control over your grow, and that includes the type of medium it grows in, like soil, hydroponic trays, and more.
For beginners, starting with soil or a soil-coco coir mix is generally recommended, as soil already contains most of the nutrients the plant needs. You may only need the occasional top-up with fertilizer, which you can do by mixing nutrients into distilled water and applying it to the soil.
Beginners may also do well with coco coir-only growing mediums, but some nutrient experience is best before this type of grow, as you will need to feed the plants yourself.
Hydroponics or aquaponics are other options, but these methods are more expensive, harder to maintain, and come with a steeper learning curve. You’ll have to learn how much nitrogen, phosphorus, and potassium each plant needs, and feed the plants yourself.
How to grow cannabis indoors
Growing cannabis from seed to harvest involves a few key steps, including choosing the right seeds, understanding your plants’ lighting and temperature needs during each growth stage, and checking in regularly to ensure your equipment is running properly.
Step 1: Choose the right seeds
The first step to growing weed indoors is to start with the right cannabis seeds. You’ll want one that is dry, dark-colored, and hard — ideally, one purchased from a reputable seed source.
When you’re buying seeds, you’ll be able to choose between feminized and non-feminized seeds. Opting for feminized seeds can save you some time, as they ensure that you only yield female plants, which produce buds. Non-feminized seeds can help for breeding purposes, but people usually get rid of their male plants if they are not breeding, because male plants don’t produce buds.
A number of cannabis varieties have been bred with indoor and discrete grows in mind. Some examples include:
- Blueberry
- Blue Dream
- Master Kush
- Northern Lights
- OG Kush
- Skunk #1
- Sour Diesel
Those just starting out may want to stick to auto-flowering seeds. These produce short, squat varieties of cannabis that can grow in colder climates, and mature when they reach a certain age rather than relying on the light cycle. Autoflowering strains are crossed with other types of cannabis (specifically, Cannabis ruderalis) to increase THC production.
Another beginner-friendly tip is to go with hybridized strains, which are more resistant to mold, mildew, pests, and other diseases. They’re also easier to grow due to their flexibility to various conditions, and can produce larger yields than non-hybridized (landrace) strains.
Step 2: Germinate and wait for seedlings to emerge
To germinate your seeds, soak them on paper plates or between paper towels, and wait for a root to emerge on each one. It can take a few days for this to occur.
Once your seedlings emerge, it’s time to transfer them carefully into the growing medium. If using soil, for example, you will transfer them to fabric pots filled with soil. You’ll want to plant them about 10 millimeters deep in the medium. This is roughly the width of a regular paperclip.
Keep the soil damp, but be sure not to overwater.
You can buy cannabis plant cuttings (clones) from a dispensary if you want to avoid the germination process. This can help you find an appropriate plant for your needs with far less work, and you can skip the vegetative growth stage entirely.
Step 3: Move into the vegetative stage
The next step is to wait for your marijuana plants to move into the vegetative stage. You will need to provide about 18 to 24 hours of daylight, along with temperatures around 70 to 85 degrees Fahrenheit.
At this stage, plants must be watered regularly, and they’ll need extra nutrients, particularly nitrogen. If you didn’t get feminized seeds, you will need to identify and remove all male plants at this point, too.
Optional advanced step: Train your plants
During the vegetative stage, more advanced indoor growers may begin training their plants using the Sea of Green (SOG) method or the Screen of Green (SCROG) method. These techniques are used to train the plant to maximize yield.
The SOG technique requires keeping a mother plant in a permanent vegetative stage and then taking cuttings periodically to propagate it. You can put these cuttings straight into a 12-hour dark, 12-hour light flowering cycle.
This can shorten overall growing times and increase the number of grows per year. This method is generally better for short, squat plants, and for creating a dense growth area.
The SCROG technique, on the other hand, involves using a wire grid, where the grower weaves the plant’s branches through the mesh. This allows the grower to redirect individual branches lengthwise across the screen and achieve a flat, horizontal canopy.
The SCROG method is ideal for large plants which would otherwise outgrow your room, and where all plants are growing to a similar size.
These techniques are generally not recommended for beginners. It’s best to get a few grows under your belt before training your plants, although the SOG technique may be possible with little experience.
Step 4: Monitor the flowering stage
In the flowering phase, female plants will develop thick, heavily-scented buds as their energy is focused on bud development. They’ll grow much larger as the buds, hairs, resin glands, and trichomes develop. This is when you move to a light cycle of 12 hours of dark and 12 hours of light.
At this stage, you’ll stop training your plants. Toward the end of flowering, you’ll stop giving them nutrients. Instead, you’ll start to flood your plants’ growing area with water only.
Depending on the type of plant, most cannabis strains finish flowering between 6 and 14 weeks. Indicas and auto-flowering strains usually finish flowering between 6 and 9 weeks, hybrids 8 and 12 weeks, and sativas 10 and 14 weeks. This is not a hard-and-fast rule, but most cannabis plants follow this pattern.
The plant’s physical appearance (phenotype) matters as well. For example, a hybrid that expresses indica will likely finish flowering sooner than a hybrid that expresses sativa.
Some people also decide when to finish flowering by looking at the plant’s trichomes (glandular hairs). This can help growers determine when the plant’s cannabinoids and terpenes are fully formed. The trichomes usually go from clear to cloudy, and then to amber.
Many people harvest when most trichomes are an even mixture between cloudy and amber. For some, harvesting too early in the cloudy stage can be undesirable, because this is when THC levels are their strongest. In contrast, harvesting when several trichomes are amber means that some THC has broken down, which can offer a more manageable experience depending on one’s THC tolerance.
Step 5: Harvest and cure your plants
After all of your hard work, you get to enjoy the harvesting and curing process. You’ll want to cut the main stem of each bud before hanging them to dry. Trimming and curing are the last steps, which can take up to 5 weeks to complete.
The bottom line: Indoor growing offers loads of advantages
Growing cannabis can be expensive in the beginning, but over the course of a year, it can save you a lot of money, as you won’t need to buy heavily-taxed products from a dispensary. You can also cultivate strains that you can’t purchase at your local dispensary.
In states where growing cannabis is legal, the maximum number of plants allowed per household is generally higher for medical marijuana patients compared with recreational users.
To grow more plants and maximize your yield, connect with Leafwell’s virtual clinic to register for your medical marijuana card today.
Frequently asked questions
Is it better to grow cannabis indoors or outdoors?
While both methods have their pros and cons, indoor growing is typically easier and gives you more control over your plants’ growing conditions, like light, temperature, and humidity. Indoor growing also means a lower risk of pests and diseases that can prevent a healthy harvest.
How long do indoor plants take to bud?
It takes several weeks for cannabis plants to produce mature buds that are ready for harvesting. The exact flowering time will depend on the strain you’re growing and the conditions of your grow space.
What do I need to grow marijuana indoors?
At a minimum, growing cannabis indoors requires a grow light, pots for your plants, and ample space for the plants to mature. You may also need an air conditioner unit, a humidifier, and other equipment depending on the type you’re trying to cultivate and how much control you want over each plant’s growing stage.
Resources
Closing the Yield Gap for Cannabis: A Meta-Analysis of Factors Determining Cannabis Yield: https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00495/full
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