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How to Grow Marijuana Indoors

Growing Medical Marijuana Indoors

Growing marijuana indoors has many advantages over growing marijuana outdoors. In a grow room you are in control of the environmental conditions from temperature to light to humidity to CO2 levels. You can adjust ambient conditions to suit a particular strain or stage of growth. Plus, your cannabis crop is much safer from theft or discovery by the authorities if you are growing illicitly.

You want to grow marijuana indoors. Before you begin there are several things you need to decide on:

How Much Space do You Need?

Grow Room Planning

Grow Boxes

Grow Tents

Will You Use a Hydroponic System or Grow in Soil?

Choosing a Growing Medium

Choosing a Hydroponic System

Dutch Grow Systems for Hydroponic Marijuana

Nutrients, pH, Lights and More

What Kind of Lights Will You Use?

Full Spectrum LEDs

HID Lighting

Other Options

Once you’ve made these decisions, you’ll be well on your way to planning out your grow room. Now you need to know what to expect as you go from choosing seeds to harvesting your first crop:

Choosing Seeds


Vegetative Marijuana

Flowering Marijuana

Harvesting and Curing Marijuana

How Much Space do You Need?

Massive Indoor Marijuana Grow Most growers will only have a specific amount of room available inside or within a weather proof area outside. The amount of space you have available will dictate several things:
  • How many plants you can grow
  • How big your containers can be
    • If you have a limited space you may choose to grow more plants in smaller containers. You’ll have a lower yield per plant but can achieve a higher yield overall, think SoG and SCROG methods.
  • How long you veg your plants
    • Marijuana plants will get larger and larger as long as you keep them on 18-24 hours of light a day. If you have a limited space and need smaller plants, switch to 12 hours of light to stimulate flowering early on. Consider strains that develop short stealth plants.
  • Which types of seeds you plant
    • Leggy Sativa’s and Hazes take up a lot of room. In a small space you may choose a short, squat Indica. Alternatively, you may choose a tall Sativa with fewer branches if you have a tall room but not a lot of space horizontally.
If you have space to devote to two separate grow rooms, you can produce a continuous crop by maintaining plants in the vegetative and flowering stages simultaneously. If you only have one space you’ll have to adjust the lighting in that room for each stage and will only be able to harvest once every 3-4 months. For more detailed information check out our grow room planning guide here.

Temperature and CO2

Getting the right temperature and mix of air so that your plants aren’t too hot, cold or humid is crucial for fast quality growing. When plants are too hot or do not get enough oxygen they start to droop and lose their color. Marijuana will tolerate temperatures between 60°F and 92°F (17°C – 33°C) however there ideal temperatures is 70°F – 83°F (21.1°C – 28.3°C). A drop of 10-15°F at night is fine, and actually improves the flavor of buds. Your plants need a fresh supply of air for optimal growing, so some sort of ventilation system is important. Some growers add carbon dioxide to their grow room to improve yields. For a small beginning grow, this is probably not worth the expense. More info on temperature, ventilation and CO2.

Marijuana Odor Control

It is essential to control the odor in your grow room. All marijuana has some smell, and if you’re growing an especially aromatic strain like the original Skunk you could have the whole neighborhood smelling! Fortunately there are a lot of great carbon filters, ionizers and ozone generators available to help you cleanse the air before it exits your grow room. Don’t forget to wash your clothes and take a shower after visiting your grow room. You might be used to the rich, dank odor, but your boss probably isn’t! More information on marijuana odor control.

Grow Boxes and Grow Tents

Grow Marijuana Indoors Grow Tent If you don’t have an entire room you can dedicate to growing marijuana indoors, consider purchasing a grow box or grow tent. There are options for all grow sizes, from a single plant up to 30! Most grow boxes come equipped with lights and hydroponic systems already set up. Many have separate chambers so you can clone, veg and flower all at the same time for a continuous supply of tasty buds.

Will You Use a Hydroponic System or Grow in Soil?

You do not have to have a full hydroponics system to grow marijuana indoors. You can grow easily in a container using soil or quality compost. This is the most basic indoor growing system. It has offers the benefits of simplicity and saving water, making growing marijuana in soil one of the most environmentally responsible methods. However, there are some clear benefits to growing with hydroponics.

Benefits of growing with hydroponics:

  • Control of Nutrients
    • With a hydroponic set-up you know exactly what your plants are eating. You can adjust the nutrients based on the particular strain you are growing or the stage of growth.
  • Lower Risk of Disease
    • Mold spores and parasite eggs can hide all too easily in soil. If you don’t sterilize your soil you may be introducing harmful pathogens into your grow room. These risks are eliminated with a hydroponic system.
  • Higher Yields
    • While the soil advocates will debate this, most growers agree they see higher yields from a hydroponic grow.
  • Less Mess
    • Soil is, well, dirty. You’re growing inside your home and you don’t want a lot of mud and dirt on the floor.

Beginner Hydroponics

To get started, here’s a little more information about hydroponics for the beginner: Hydroponics simply means growing plants without soil. Plants take in nutrients as simple inorganic ions dissolved in water. Soil acts as a source for these ions, but soil itself is not necessary for healthy plant growth. By artificially adding nutrients to a plant’s water supply, soil becomes unnecessary. There is a little more to hydroponics than just adding nutrients. While a plant needs water to absorb its food through its roots, it also needs oxygen around the roots. If you submerge a cannabis plant’s roots in water with no source of oxygen it will eventually drown. There are many different hydroponics systems available.

Choosing a Growing Medium

This is the substrate that replaces the soil. Some hydroponic systems like Deep Water Culture don’t require any medium at all. For others you can choose between many different options including Rockwool, perlite, clay pellets, coco fiber or a combination of these. To help you choose the best medium for your set-up, check out our page on growing mediums here.

Choosing a Hydroponic System

Hydroponic Drip Set-Up Marijuana There are so many different types of hydroponic systems for growing marijuana indoors. From the basic wick method which does not involve any pumps at all to the more intricate Aeroponics method with full misting emitters, there is an option for every grow room design and every level of expertise. With any hydroponic system, your goal is to promote healthy roots, because healthy roots = big, healthy buds.
  • 1. Aeroponics – The roots of the marijuana plant are held in a water tight, dark box with small nozzles emitting a fine mist of nutrients over them. This gives a humid but oxygenated area for the roots to flourish without being completely immersed in water.
  • 2. Continuous flow– Or the Top Feed system. This is a common DIY hydroponics system which uses a PVC pipe with holes cut at intervals. The young marijuana plants are grown in the holes, and water with nutrients continuously runs through the pipe.
  • 3. Deep Water Culture (DWC)– The roots of your plant are situated within the nutrient solution. Remember, roots need oxygen. In a DWC set-up you need to add an air stone to oxygenate the nutrient solution.
  • 4. Drip Irrigation– A very effective way to grow with small emitters dripping the nutrient solution directly into the pot near the roots. This saves water, evaporation is near zero and it is highly effective as the roots get nutrients and also air.
  • 5. Ebb and Flow– The Ebb and flow system works with your plants sitting in a tray above a reservoir of nutrient solution. The nutrient solution flows into the tray, the roots take what they need and the rest of the solution flows back into the reservoir below.
  • 6. Nutrient Film Technique (NFT)– Similar to the Ebb and Flow situation above but the tray is tilted so the nutrients are a thin film of liquid and constantly flowing past the roots.
  • 7. Wick system– The marijuana plants are in pots which can have any grow medium in them, including soil (granted, then it’s not technically a hydro system). A thick wick of cotton connects the pots to a reservoir below. The roots can suck up the nutrient solution as they need it via capillary action.

Dutch Grow Systems for Hydroponic Marijuana

There are two systems designed by Dutch growing masters to boost yields. They require a little planning in advance, so you may want to consider setting up your grow room with one of these methods in mind.

Sea of Green (SOG)

SOG method incorporates how the Dutch masters create a fast yield in super quick time. They force the plants to flower at around two weeks old, it saves space and speeds up the grow cycle. More info on Sea of Green.

Screen of Green (SCROG)

SCROG is very similar to the SoG method above and also extremely productive. The difference is using screens to spread the leaves out so more light reaches the entire plant. More info on Screen of Green. Grow Marijuana Indoors SCOG

Nutrients, pH and More

Deep Water Culture Grow Indoors

Hydroponic pH

It is important to maintain a neutral pH for your plants. Often tap water is alkaline or acidic. If you let it stand for two or three days to neutralize before adding it to your reservoir, you’re usually safe. However, it is best to monitor the pH so you know exactly what is going on. More info on hydroponic marijuana pH.

Hydroponic Nutrients

Most growers purchase their nutrients from a hydroponics shop or online. Marijuana requires the same nutrients as other plants: nitrogen (N), phosphorus (P), potassium (K) and a variety of trace nutrients. Most nutrient packages list the three big ones in order N-P-K. For instance, 10-5-5 means 10 parts nitrogen to five parts each of phosphorus and potassium. More info on hydroponic nutrients. For a successful grow you’ll need to choose the right nutrients, monitor the pH levels of your solution, manage pests and mold and, of course, use the proper lighting. This can all be a bit overwhelming for a beginner. For your first grow (or three!) consider a full grow box kit which will include everything you need to get going. Learn more about growing hydroponic marijuana with our Hydroponic Grow Guide.

What Kind of Lights Will You Use?

Healthy Hydroponic Indoor Grown Marijuana While you don’t need a hydroponic kit to start growing beautiful flowering cannabis in a closet, cupboard or spare room, you will need a good grow light. While there are several types of grow lights, these two are the best options for an indoor grow:

Full Spectrum LED Grow Lights

Full Spectrum LEDs are rapidly becoming the most popular grow lights available. They cover the entire spectrum of light used by growing plants, from 420 nm right through 750 nm. There are peaks throughout this spectrum that plants utilize for photosynthesis. By aligning the spectrum of each LED to match these peaks, nearly all the light emitted by these grow lamps can be used by the plant. That means little waste, better yields and lower electric bills. Massive LED Grow Light Yearly Review LED grow lights tend to cost more up front than High Intensity Discharge (HID) lights, but they save a bundle on light bills later on. Another benefit of using full spectrum LEDs is that they don’t lose energy as heat, so you don’t have to worry about burning your plants. To learn more and read reviews of the best grow lights on the market, check out our Full Spectrum LED Grow Light Guide.

HID Grow Lights

The improvement in LED technology is new. Until now, HIDs were the best option for an indoor grow, and they are still incredibly popular. Generally you need two different types of HID lights for each grow:
  • Metal Halide (MH) These lights are perfect for the vegetative stage, as they have mostly green and blue spectrum light.
  • High Pressure Sodium (HPS) HPS lights can be used for the entire grow cycle, but they excel during the flowering stage thanks to their high levels of yellow and red light.
HID lights are less expensive to purchase than full spectrum LEDs. They do emit a lot of heat, so you will need a good ventilation system. The lights must be elevated as the plants grow to avoid burning the uppermost leaves. Learn everything you need to know in our HID Grow Light Guide. Now you’ve got your grow room set-up. It’s time to pick out seeds and start growing.

Choosing Marijuana Seeds

You may choose to start growing from clones if you have access to a reliable source. However, we recommend growing from seed until you have your own mother plant. That way you know exactly what you are getting. After all, good genetics make all the difference in the size and quality of your harvest. To get started, make sure you know the difference between Sativa and Indica strains. Then you’ll have to choose between Regular, Feminized and Auto-flowering strains.
  • Feminized seeds – When you’re starting out, we recommend that you buy feminized seeds. Feminized cannabis seeds are chemically treated so that they grow to become females. This means you don’t have to worry so much about sexing your plants and throwing out the males. Later on, when you may be interested in breeding your own new strains, you’ll want regular seeds. Full marijuana seeds guide.
  • Auto-flowering marijuana seed - strains have been around for some time now and are a great choice for indoor growing. Auto-flowering seeds are not light dependent. They will start flowering after a certain amount of time, regardless of how much light you give them. They tend to be smaller and faster than regular strains, and you can have vegging and flowering plants all together in a single grow space.

Marijuana Seed Germination

Germinating Marijuana for Indoor Growing This is where it all starts! One of the best methods for indoor growing is to the seeds off in a small amount of Rockwool, they then grow into the small cube which you then place onto the growing medium. The marijuana seedlings then grow straight through the Rockwool into the substrate below. You can also start seeds germinating in moist paper towels. Learn everything you need to know about marijuana seed germination.

Vegetative Marijuana

Once they germinate, your seedlings will enter the vegetative stage of life. During this stage the plant grows a strong stem and lush foliage. For most strains you can maintain this stage as long as you like by keeping the lights on between 18 and 24 hours a day. Mother plants for making clones are kept in the vegetative stage perpetually.

Vegetative marijuana has a few special requirements:

  • More Blue and Green Spectrum Light
  • Humidity at 45-55%
  • Temperatures 75-80°F (10-15° drop at night is fine)
If you are using regular seeds, look for male pre-flowers between 10-14 days. You can adjust this stage to grow smaller or larger plants. For example, if you are using the Sea of Green method you would induce flowering in as little as two weeks. If you want a high yield from one or two plants, you’d let them veg for several months. More information on vegetative growth

Flowering Marijuana

When you switch your lights to 12 hours on, 12 hours off, your plants will begin to flower. Learn all about the marijuana light cycle here. Depending on the strain you’ve chosen, flowering can finish in as few as 7 weeks or take up to 16 weeks. Flowering marijuana needs:
  • More Red Spectrum Light
  • Early in Flowering: Lots of Nitrogen
  • Middle of Flowering: Less Nitrogen, High Phosphorus
  • Slightly Lower Humidity
Ideal flowering conditions will vary considerably depending on the strain you are growing. Strains with dense, tight buds need lower humidity to avoid bud rot. Some strains are sensitive to overfeeding during flowering and can suffer nutrient burn, while others need a lot of nutrients to produce their optimum yield. Learn more about nutrient cycling for marijuana here.

Harvesting and Curing Marijuana

This is the part you’ve been working so hard for! The basic process is simple:

1. Time the Harvest

This is the hardest part of all. If you harvest too early you miss out on resinous THC crystals that develop toward the end of flowering. If you harvest too late some of that juicy THC has already denatured. An artist’s loop or magnifying glass is essential to timing your harvest perfectly. You need to look at the color of the trichomes to determine the readiness of each plant.

2. Cut the Plants

This part is easy. You can cut the main stem, cut each branch individually or pull up the entire plant. It is best to cut the plant in smaller pieces so they can dry without touching each other.

3. Hang to Dry

Marijuana needs to be hung upside down in a room with good air circulation and allowed to dry. Depending on the temperature, humidity and ventilation in your drying room this can take anywhere from a few days to a few weeks. It is ready when the stems crack rather than bend between your fingers.

4. Trim

Trimming is largely personal and depends on how manicured you want your buds to look. Don’t throw out the trichome rich sugar leaves you remove. These can be smoked or made into hash or edibles.

5. Cure

While your bud is smoke-able after drying, it will get better if properly cured. Place it in an air-tight glass jar. Open the jar so it can breathe for 15 minutes twice a day. This allows the terpenes and flavonoids in the bud to fully develop, enriching the smell and flavor of the bud. Don’t let too much oxygen in, or the THC will start to degrade. After about a month you’ll have prime smoking bud. For more information, check out our marijuana harvesting guide here.

Basic Marijuana Grow Using Nutrient Film Technique

There are a lot of options when it comes to growing marijuana indoors and with hydroponics. Here is a detailed description of one of the most effective indoor hydroponic methods, the Nutrient Film Technique. You may want to try it out for your first grow:

Nutrient Film Technique (NFT)

In this method, the plants grow through light-proof plastic films placed over shallow, gently sloping channels. A steady flow of nutrients is maintained along the channel, and the roots grow into dense mats, with a thin film of nutrient passing over them (hence the name of the technique). One downside of the technique is that it has very little buffering against interruptions in the flow such as power outages; but overall, it is one of the more productive techniques.

A Basic NFT Set-Up Includes:

  • LED full spectrum grow lights with a total output of approximately 50 to 250 Watts or a high pressure sodium lamp (600 Watt is the most efficient but a 400 Watt may suit a smaller space);
  • Fan and ventilation exhaust systems running 24 hours a day if possible. No need with the LEDs as they produce very little heat;
  • Buy some seeds, germinate them and now you have seedlings in pots situated in your tray using your chosen grow medium. Try a basic mix of 50% potting compost 50% Perlite. Raise the pots in the trays with bricks or wood so they don’t sit in a puddle once watered, they need drainage to keep oxygen flowing and help them grow. OR Use a NFT tank with pump and spreader mat (these come with the tank), Rockwool cubes.
  • 24 hour timer to control light cycles. This should be used with a high power switch known as a contactor or relay switch as grow lamps can easily burn out regular timers used on their own;
  • A pH tester to test water and nutrient feed solutions to adjust water and feed solution to around pH 6.0 – 7.0;
  • Nutrients, ones aimed at growing the plant during the vegging stage and then usually a different solution when it comes to flowering or budding;
  • Matt white paint or white plastic to cover the walls of the grow space to help reflect light back onto the plants.
Also useful are a measuring bucket, measuring jug, large syringe and pea netting or string to support top heavy plants. If you can afford it a great help is a Total Dissolved Solids (TDS) meter. These allow you to check the nutrient levels of feeding solutions to make sure they are optimized for your plants. Growing hydroponically in a Nutrient Film Technique (NFT) Tank is really simple and not something to be afraid of. In fact some beginners to growing may find it easier than using soil mixtures in pots. You do not have to judge if the plants need watering or feeding so much using NFT, as long as you follow the simple instructions supplied with the tanks the plants should look after themselves.

Enjoy Growing Marijuana Indoors

Apartment Window Growing Marijuana Indoors You’ve got all the resources you need to get started. Don’t be intimidated by growing marijuana indoors. You’ll learn quickly and soon find yourself growing new and exciting strains or teaching your friends.