Learn how to grow weed indoors with this step-by-step guide that'll teach you exactly how to turn a seed into a smokable dried flower. Free eBook included. Growing weed indoors is a great option for new homegrowers. Learn everything you need to know about growing weed indoors, including how to set up your grow room and climate control. A Step-By-Step Guide to Growing Marijuana Indoors
How to Grow Weed Indoors for Beginners [Follow-Along Guide]
I’m here to tell you that growing weed indoors step-by-step is easy. Just follow along.
Because it’s the first choice of thousands of beginner growers, I’ve decided to put together the most comprehensive soil weed growing guide on the internet.
In this guide, we will go through the whole growing process, from choosing the seeds and soil to harvesting and curing the buds. Hopefully, by the end of this guide your cannabis growing knowledge will grow as much as your plant.
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The first week (or week 0 as I like to call it) is when you prepare your grow.
It doesn’t necessarily have to be a whole week, however it can often be longer.
You might think:
“So, it’s not a week at all?”
And you’d be right.
You won’t be doing any growing this week as you can’t grow plants without the seeds first.
Week 0 is focused around finding the best soil, seeds, lights and setting up your growing tent.
Even if you are growing hydroponic marijuana you have to do the prep stage, which might be even longer for hydroponic setups.
For this indoor soil growing guide we will use one of the most popular strains ever: White Widow.
But, we won’t use just any White Widow.
For this occasion we will use the autoflowering version of this plant.
Well, for a few simple reasons:
Autoflowering plants are smaller, but they don’t cut down on the yield, they are easier to grow, and they grow faster than regular plants.
You will want only feminized seeds for this grow as male plants do not grow flowers.
“Your plant is only as good as your soil.”
I find this to be one of the biggest truths of growing cannabis.
Beginner growers often experience problems with their soil, such as malnutrition and over-watering.
Both of these will have a long term effect on your plant if not dealt with in the quickest manner.
This is not to say that cannabis won’t grow in slightly bad conditions, far from that.
It’s called “weed” for a reason. It will grow even in sub-par conditions, however the end result might not be what you hoped for.
So, in order to avoid any confusion, do your best to get the perfect soil, and if you fail, you can still make it up by adding nutrients.
Feel free to buy any of the branded soil mixes, except for those that are labeled “extended release”as they will release nitrogen to your plant roots for up to 6 months, meaning that you will have n0 control over the pH levels of your soil.
The best option out there for first-time growers is “Super Soil”, a special mix of soil that can be found in stores. KindSoil is one of the more popular brands of Super Soil.
With any Super Soil mix you won’t have to add any nutrients, as the mix comes premade, so water will be the only thing you add to it—by watering the plants.
Did you know that earthworms in soil can increase the yield up to 75%? According to scientists from Netherlands, earthworms might be one of the most important parts of a soil-based grow.
However, this study was done on wheat plants so I wouldn’t suggest you throwing earthworms in the mix if you haven’t had at least a dozen successful grows.
Lights are super important for growing cannabis and insufficient lighting is one of the biggest reasons why many indoor grows fail.
Lighting depends totally on the size of your grow.
Basically there are 2 most common options for lighting:
- CFLs (Compact Fluorescent Lights).
CFLs give off more heat than LEDs and are better suited for growing in small spaces, such as tents.
Their downside is that they tend to spend more energy and you will have to readjust them more often than LEDs.
So, my end recommendation is this: if you have room for LEDs and you are willing to go through the hustle of setting up LEDs, be my guest.
For a small first time grow, I would suggest getting a CFL setup with lights up to 300W.
Keeping CFLs close to the plants will bring in the best yields and ensure the biggest plant growth.
Growing tents are perfect for those that tend to grow in their garage or colder areas of the house, as the tent holds the warmth within itself, helping plants get bigger as soon as possible.
If you plan on growing marijuana in a closet, or a similar closed space that doesn’t let too much heat out, I would suggest that you approach it with caution.
Either way, the most important thing is to keep the temperature at a constant 25°C (77℉).
In case you do go with a tent, you will have to extract the air from the tent, which is removed using a fan that sucks the air out through tubes.
Most modern tents have a carbon filter which prevents the smell of weed leaving the tent, so keep that in mind when shopping for one.
If you still think you can make do without a tent, then get ready to spend some money on fans and/or ventilation systems.
Most modern air extractor fans include temperature and moisture controllers, which will come very handy when calculating your VPD (we’ll get to that later), so I strongly suggest you get one of those.
Pro tip: if you have cats you are going to want to get a tent. Just trust me on this one. I’m saving you money, effort and a lot of nerves.
Light schedule for growing weed indoors
Light periods for autoflowering plants are really easy to grasp:
All you have to do is keep the light turned on.
Like, all the time.
I am not joking when I say that you should keep the lights on 24/7.
Giving 24 hours of light is crucial when growing autoflowering plants, as it may give them the best chance to grow bigger in the vegetative stage and then eventually flower when their time comes.
Autoflowering plants do not need darkness.
Autoflowering plants are not dependent on changes in the light cycle to commence flowering.
This is why they can be grown using a light cycle of anything from 16 to 24 hours daily.
This is also what makes them perfect for first time growers as light periods are one less thing to worry about.
Germination & seedling stage
Time to put those girls into action!
But first, some more prep.
VPD for weed
Creating the perfect environment for your plants doesn’t necessarily end with buying all the right gear.
You will have to know how to properly set it up, and more importantly, how to make the perfect atmosphere for your plants to grow to their potential.
Dehumidifiers decrease environmental moisture and release heat, which can be helpful in certain cases like very moist and cool areas, such as basements.
If you want know how to grow big buds indoors, you have to understand the importance of VPD.
Whether you are growing weed in a closet or a tent, you will have to control the atmosphere.
Humidity is one of the more important factors to control and this is in part due to the fact that different humidity levels are best for different growing stages.
In general, the air humidity for growing weed indoors is as follows:
One thing which is closely connected to air humidity is VPD.
VPD stands for Vapor Pressure Deficit, and it represents the difference between the pressure of water vapor in 100% saturated air at a certain temperature (leaf’s vapor pressure) and actual vapor pressure in the air surrounding the plant.
Plants with higher VPD values will generally have a higher transpiration rate and increased nutrient movement.
Germinating weed seeds
Learning how to germinate a weed seed is a piece of cake, and also the first step you will take towards your new hobby.
Germinating seeds is a process of forcing them to begin to grow and put out roots.
Seeds can be germinated in many ways and the first time you do it you will get a hang for it because there isn’t really too much science behind it.
How to germinate weed seeds?
There are several ways to do this.
Germinating seeds in soil
Germinating seeds in soil is the easiest way to do it because all you have to do is toss them in your pot, cover with some dirt and douse with water.
You only need the soil to be damp so make sure you do not over water it. You can use clear kitchen plastic to wrap the tops of the pots to maintain humidity. Keep the pots in a warm area.
Germinating seeds in water
Germinating seeds in water requires even less effort than germinating seeds in soil.
You literally just have to throw them in a cup of water for 14-18 hours.
One thing that makes this way better than germinating in soil is that you can see if a seed is bad by checking if it didn’t sink. Those that sink are good.
After the seeds start rooting, move them on a damp paper towel and cover with another damp paper towel.
Place the paper towel covered seeds in a dark area and they will grow roots in a matter of days.
After that, all you have to do is move them into a pot.
Germinating seeds with paper towels
For this method, you take a couple of seeds, put them on a damp paper towel and cover with another one, after which you store them somewhere dark.
After a few days you should see roots embedded in the paper towels.
You can do this with gauze and cotton wool as well.
Seedling stage begins once you’ve moved your seeds from the paper towel into the pot and you start seeing the first leaves break out from the ground.
Here’s a photo of a plant a few days into its seedling stage:
That is exactly what your plant will look like maybe a week after you’ve moved the seeds into the pots.
You don’t really have to do much during the seedling stage.
You don’t even have to water the plants too much as you’ll want the soil to be a bit dry so that the roots can catch better.
You might be thinking, “This man is crazy!”, and you’d be right.
But, letting your plant root strong is a great idea during the seedling stage, just make sure you don’t over water and suffocate the plant.
Over-watering is one of the biggest mistakes you can make, but we’ll get to that in a bit.
One of the most important things to remember for the seedling stage is that you will want to move your plants in a bigger pot as soon as you see the first few leafs show.
Knowing how and when to transplant your plants is perhaps the best knowledge we can pass onto new growers, as leaving plants in small pots can choke them up, while moving them too early can have terrible effects, especially if you don’t do it right.
Further along the road you will most likely have to re-pot the plants again.
I strongly suggest you move the plants as soon as you see the first leaves appear.
The second re-potting should happen once your plants have rooted in firmly and appear ready to be moved—this means that the plant looks stable enough to be moved.
Whatever you decide to do regarding re-potting, keep one thing in mind: The less root damage the better.
Vegetative stage starts when you see that the plant is looking more like a weed plant than just a regular plant, meaning that it has clear weed-like characteristics.
You will start seeing the recognizable fan leaves and many branches stemming from the trunk, alongside that familiar skunky smell.
Vegetative stage starts roughly around the second week for most autoflowering plants, but for others it might start in the third week.
Either way, once your plant starts growing in size by the day you will know that you successfully reached the vegetative stage.
Watering weed plants
Watering weed plants is a tricky business if you’ve never watered plants in your life.
Most growers water their plants from the tap so there aren’t really any reasons why you shouldn’t do the same.
The amount of water you will use for your plants varies depending on the specifics of your grow and the environment in which you hold the plants.
It also depends on the size of the plant, air temperature, soil composition, water quality and the capacity of your air filtration systems.
However, seeing how this is intended for beginner growers we won’t go in depth too much with watering.
Let me just leave it at these 3 things:
- Water whenever you feel that the top of the soil is dry
- Bigger pots — water less often, smaller pots — water more often
- Make sure you have appropriate drainage (to avoid overwatering)
Pro tip: Get yourself a bottle of carbonated water, and sprinkle the weed leaves. Carbonated water has CO2, which your plants crave.
How to clone weed plants
Similarly to re-vegging autoflowering weed strains, cloning them is extremely hard or next to impossible to do.
This is due to the fact that autoflowering strains have grown in the northern areas of the planet in which they had limited time to flower.
Cloning an autoflowering seed will create a plant of the same age as the mother plant.
Clones share the exact same genetics as the mother plant, which includes their age.
So, if this is your first grow, chances are that you won’t even try cloning a plant.
If you’re growing a photosensitive strain, however, cloning should be a piece of cake.
- Contrary to popular opinion, don’t cut off the most bottom node. Cut at least the 2nd or 3rd node.
- Fill a solo cup with soil and punch a hole on the top of the soil about 10 cm deep.
- Shave off a bit of the skin on the bottom of the cutting so it can form roots more easily.
- Stick the freshly cut branch in the hole you just punched and water your new plant.
Cloning weed plants is a great way to save money and keep growing the same plant with great genetics over and over again. You can clone one plant as many times as you want, and the clone of that clone.
Hell, cloning works even with cats.
Once your plants reach a decent height and size it is time to flower.
Since we are growing an autoflowering strain, you won’t have to put any effort into changing the light schedule or anything.
Once your plant feels the time is right, it will start flowering.
How to know if your plant is male or female?
“Feminized cannabis seeds are bred to contain no male chromosomes, thus ensuring that every plant grown from them will flower as a female and be able to produce the crop of resinous buds sought by most growers”.
But, what happens if you buy random seeds which aren’t feminized?
Well, in that case you will simply have to sprout all the seeds, and wait for them to grow up a bit.
There are some general rules that will help you determine the sex of your weed plant:
- Male plants mature faster, most of the time about two weeks before females;
- Male plants also have “false buds” which are actually pollen sacs;
- Male plants have flowers while females still have pistils at this point.
It is important to keep in mind that cannabis plants can also be hermaphrodites, which means that one plant has both male and female traits.
Pro tip: It is very important that you keep male and female plants separate (or toss the male plants away) as there is a chance that male plants might ruin your grow by fertilizing the female plants.
Most autoflowering plants will show best results around the 11th or 12th week, which is usually a great time to harvest.
But, before you cut your flowers and start drying, here are 2 things to know before you throw away the remaining pieces of the plant:
- Harvested plants can grow again and bring more crops (unless they are autoflowering strains) by re-vegging the plant;
- You can still clone the plant that you just cut up as long as there are healthy leaves.
Make sure that you don’t rush too much with harvesting, as cannabis needs time to develop higher levels of THC, so harvesting a bit later is a lot better than harvesting too soon.
How to re-veg weed plants
To reveg a weed plant means to send it back to the vegetative phase right after the harvest.
Now, I know I said that we will be using an autoflowering seed for this, and the common knowledge is that autoflowering plants cannot be re-vegged.
However, let us pretend again for a minute that we started with a photosensitive seed, in order to show you how re-vegging works.
You might wonder:
“Why reveg weed when you’ve already harvested the plant?”
There are multiple answers to this question:
- If you had a great yield and you want to repeat the same results;
- If you don’t want to spend money on new seeds;
- If you want the same genetics but different results.
So, in order to re-veg the plants you will first have to harvest it.
- Cut off all the bigger branches and just leave the trunk of the plant snapped with a few of the smaller branches remaining
- Those smaller branches should have a few flowers on them. From these flowers you will see new leafs appear and grow once the plant starts to re-veg
- Put the plant back into the growing room and give it 18 hours of light.
You will see new branches appear from the old flowers and once it hits a decent size, put it back to 12 hours of light and 12 hours of dark so that it may flower.
Most plants that get re-vegged will start growing in a bushy manner rather than straight up as they used to.
This is a slow process so don’t be hasty and take your time taking care of the plant as it is a hard process for the plant as well.
How to dry weed
There are 2 things to keep in mind when drying weed:
- The room has to have a certain level of humidity, which is around 50%-60%;
- The optimal temperature for your drying room is 21°C (70°F).
For best results, you should dry your buds slowly over the course of 3-7 days.
The drying time depends heavily on the climate in your area. In high-humidity climates the drying process will likely last longer, and vice versa.
Experienced smokers know how a properly dried bud feels in the hand, so if you are not certain don’t be afraid to ask.
Here are a few rules to keep in mind when you’re drying buds:
- Keep the area clean and dust-free;
- Control humidity and temperature (50%-60% and 70°F or 21°C);
- Remove the big leaves and hang the pruned colas and buds upside down on a clothing line or wire;
- Keep them properly spaced out, especially in relatively humid drying rooms;
- Move the nugs to the curing jars once the twigs start snapping.
Once you’ve moved your buds to the curing jars, the curing process begins.
If you wanna read in depth about drying weed, click here for our full article on how to dry weed.
How to cure weed
Curing marijuana buds is the last step in producing a smokable flower. After curing, your weed will have a much more impressive smell and taste.
Here are some of those big truths about properly drying and curing marijuana:
- This process breaks down chlorophyll and improves taste and smoothness of the smoke;
- It will bring out the specifics of your strain when done right, such as the smell and fine flavors;
- Less chances of mold appearing on your buds.
Check out the photo below for a comparison of well dried and cured weed and poorly dried and cured weed.
Here’s a 5 step tutorial on how to cure weed:
- Trim off the smaller leaves and stems that you find remaining after the drying process;
- Place the buds in an airtight mason jar, but make sure you don’t cram them up inside. They need some space to cure properly;
- Place the jars in a cool, dark place, and make sure there is no sunlight as it breaks down cannabinoids. Make sure you take off the lids every day for 60 minutes to get the fresh air in;
- Control the temperature (around 70° Fahrenheit or 20° Celsius) and humidity in the jars around 60% by using humidity packs;
- Cure your buds for at least 4 weeks to get the optimal potency and taste, and if you aren’t in a rush you can cure for 6-8 weeks for high-grade buds.
Many people have used small refrigerators for curing weed, as it is fairly easy to control the environment within with heat and humidity packs.
Curing weed in a fridge might be a great way to start if you’ve never done it before.
It is easy, it is convenient as little to no smell is left behind, and there is no way the light will come in.
Now it’s up to you to get started and go wild.
Growing weed can be a great hobby for all those that have enough time and passion for smoking cannabis.
Young adults do it all over the US and Canada, just as much as retired folks because it doesn’t require much to be good at it.
Experience is perhaps the biggest factor in growing weed, so don’t be surprised if your first crop doesn’t yield much or the buds don’t look like the ones you buy in a medical dispensary.
These things depend on just about everything, from the strain you are growing to lamps that you use and how long you dried and cured buds after harvesting them.
If you ever get stuck, or things start going south (leaves going yellow, mites problems, etc.) don’t be afraid to ask for help. There are people out there just waiting to hear your problems and see your plants. Many Facebook groups are named “Growers helping growers” so it might be a great idea to join one, just in case you need advice and assistance over the course of your grow.
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.
Can you grow weed indoors without grow lights?
Just about all indoor weed growers use grow lights for their plants. Grow lights ensure your weed plants will grow healthy and strong, while maximizing yields.
In theory, as long as a cannabis plant can get at least 6 hours of full sun a day, whether inside next to a window, or outside, you don’t necessarily need a grow light, but pretty much all indoor growers use them.
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.
How to regulate temperature and humidity when growing weed indoors
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.
How cold can weed plants handle?
When temperatures fall below 50°F, it can slow a weed plant’s growth and negatively impact the plant. Colder still and the plant could freeze.
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.
Soil temperature for cannabis
Soil should be in the 65-75°F range, or about the temperature of your grow space. If it seems like soil is getting too hot under grow lights, add some water on the cold side next time you water.
What soil temperature is too hot for weed plants?
A soil temperature above 80°F for a plant isn’t ideal. When soil gets that hot it can be difficult for roots to uptake nutrients.
Hydroponics is a system of growing weed without soil. Plant roots are suspended in water, which is constantly recycled throughout the system. One of the main benefits to growing hydro is that roots have easy access to nutrients. Many argue that you can grow bigger, more potent buds with hydroponics.
Can you grow weed indoors without hydroponics?
Hydroponics is an advanced form of growing that experienced growers may take on, but indoor growing can be done with soil and pots for all levels of growing experience, and is much cheaper and easier than dealing with hydroponic systems.
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.
Best water for growing weed
The cleaner the water, the better for your plants, but you don’t need to buy a bunch of distilled water. Generally speaking, if you’re only growing a few plants and your tap water is good enough to drink, it’s probably fine for your weed plants.
You can invest in an EC (electrical conductivity) meter, which measures the dissolved salts of your water, to be sure. Plain water should be between 50-300 ppm.
Ideal water temperature for growing weed
Water shouldn’t be too hot or too cold—keep water temperature between 65-75°F. Cold water can shock the plant and make it difficult for roots to absorb. Excessively hot water can damage plants.
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.
Do weed plants like warm or cold water?
If anything, use water on the cold side, rather than the hot side. Under 65°F will slow nutrient uptake, but water above 75°F can damage a plant.
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.
Growing Marijuana From Seed To Harvest Indoors
Article written by
Dipak Hemraj Head of Research and Education
Dipak Hemraj is a published author, grower, product maker, and Leafwell’s resident cannabis expert. From botany & horticulture to culture and economics, he wishes to help educate the public on why cannabis is medicine (or a “pharmacy in a plant”) and how it can be used to treat a plethora of health problems. Dipak wants to unlock the power of the plant, and see if there are specific cannabinoid-terpene-flavonoid profiles suitable for different conditions.
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