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How to Grow Cannabis Indoors

Are you interested in learning to grow cannabis? Leafwell can help you to get started.

You can check out all the essentials about growing cannabis, where we go through the plant growth cycle, nutrients and different growing mediums. We also go into outdoor, greenhouse and outdoor grows. In this blog, we will go through some of the essentials you need to know about growing cannabis indoors.

Table of Contents

  1. Set Up Your Grow Room
  2. Choose Appropriate Lights
  3. Soil vs. Hydroponics vs Aquaponics
  4. Sea of Green (SoG) or Screen of Green (ScrOG)?
  5. Choose a Variety of Cannabis That’s Vigorous and Hardy

Set Up Your Grow Room

For this, you will need a suitable setup space. This could be a spare room, a garage or a basement. Note that some states require that cannabis plants are grown out of sight of the public so bear this in mind when you’re choosing where to set up your grown room.

You will also need a grow tent, unless you have decided to dedicate an entire room to growing cannabis. Cupboards can be useful as well, but you must ensure that the gaps are plugged to prevent light from getting in. This is something you have to be wary of if you use an entire room to grow as well. Cannabis needs dark time, so if light gets in during this time, it can stress the cannabis out and cause hermaphroditism. This can lead to self-pollination.

A grow tent is a special tent that is black on the outside to prevent light from getting in, and has a refractive material on the inside to get the most out of your lights.

Other things you will need are:

  • Lights of suitable wattage.
  • A platform to place your plant pots on.
  • Plant pots of various sizes
  • An extractor fan to take hot air away from the top of the area.
  • An intake fan to pump new air into the room.
  • Carbon filters to reduce the smell of cannabis – attached to your extractor fan.
  • A thermometer. – you will want to keep your plants at a temperature of between 26 and 28 degrees celsius (around 79 to 83 degrees Fahrenheit).
  • A hygrometer (humidity gauge).
  • A timer can be used to switch lights on and off when you are not at home. Timers can also be useful for feeding in a hydroponic grow system.

You will also need to consider the size of your grow room. Most people start with a small, manageable grow room of around 3 feet by 3 feet, which can hold between 4 and 9 plants. You only require one light to cover such a room, and it is often best to start small to understand the cannabis plant’s growth patterns better before moving onto bigger projects.

2 cannabis plants in an indoor hydroponic setup.
Indoor hydroponic grow in agrow room. By Plantlady223 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=46098597

 

Choose Appropriate Lights

For the vegetative stage of your grow, you will want a grow light of around 100 – 125 Watts. To trigger flowering (after around 4 – 6 weeks of vegetation), you will want a grow light of about 250 Watts and above. Other things you will need for your light include:

  • A ballast to regulate and control the supply of energy needed to power the light.
  • A reflector surrounding the top of the light to direct the light downwards towards your plants.
  • A lamp of suitable wattage. For smaller grow rooms without much head room, you will want to keep the wattage between 250 and 400 watts. Too high a wattage, and it can actually diminish returns, as the room gets too hot.
  • Material strong enough to hang your lights, e.g. a heavy chain.

There are also different types of lights, filled with different gases. During the vegetative stage, most opt for metal halide lights as they produce more blue light. During flowering, sodium lights are preferred as they produce more red light. Fluorescent lights can be useful for plants when they are young and in the seedling stage, and for propagating plants (that is, creating a new generation of plants).

LED lights are becoming more commonplace as they are more energy efficient, don’t need to warm up, and can be used throughout the growing process, but can have a large upfront cost.

There are supplementary grow lights like plasma and CDM, which can enhance bud production, but these are not necessarily required for smaller grow rooms.

Fluorescent grow lights.
Four F32T8 32 watt lamps. Fluorescent grow lights used for indoor gardening. Author: Dennis Brown. CC BY-SA 3.0. From: https://commons.wikimedia.org/wiki/File:Fluorescent-grow-lights.jpg

 

Soil vs. Hydroponics vs Aquaponics

One of the advantages of growing cannabis indoors is that you get a high degree of control over the plants in your grow room. You can control the nutrients, the lights and how much water the plant gets. You can maximize your yield this way.

However, with this amount of control comes responsibility, especially when it comes to hydroponic and aquaponic grow systems, where you have to learn how much nitrogen (N), phosphorus (P) and potassium (K) each plant needs and feed them yourself.

For beginners, it is generally recommended to start with soil growing, as soil already contains most of the nutrients the plant needs, and you may only need the occasional top up by mixing some nutrients into distilled water and applying it to the soil.

A hydroponic system in a grow box.
A hydroponic system in a grow box. Author: D-Kuru/Wikimedia Commons. CC BY-SA 3.0.

 

Sea of Green (SoG) or Screen of Green (ScrOG)?

SoG and ScrOG refer to the techniques used to train the plant in order to maximize yield.

The SoG technique requires keeping a mother plant in a permanent vegetative stage, and then taking cuttings from the mother plant (propagation). You can put these cuttings straight into a 12 dark/12 light flowering cycle. This can shorten overall growing times and increase the number of grows you can do in a year. The SoG method is generally better for short, squat plants and creating a dense area of growth.

The ScrOG technique 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.

Cannabis grown using Aeroponics and Sea of Green method.
Cannabis being grown in aeroponics set up using the sea of green (SOG) method. From https://pxhere.com/en/photo/1190580. CC0, Public Domain.

 

Choose a Variety of Cannabis That’s Vigorous and Hardy

There are many cannabis varieties that have been bred with indoor and discrete grows in mind. Some examples include:

  • Skunk #1
  • Northern Lights
  • Blueberry
  • Blue Dream
  • Master Kush
  • OG Kush
  • Sour Diesel
  • Autoflowering (Ruderalis) strains – these are short, squat varieties of cannabis that can grow in colder climates and mature when they reach a certain age, rather than light cycle. Autoflowering strains are crossed with other types of cannabis to increase THC production.
Sour Diesel cannabis / marijuana / weed strain.
Sour Diesel. From https://www.weedshopinc.com/product/sour-diesel/. CC BY-SA 4.0.

 

These strains are hybridized, so are more resistant to mold, mildew, pests and other diseases, are easier to grow, and can produce larger yields compared to non-hybridized (landrace) strains. You can also find feminized versions of many of the above strains, which means you do not have to get rid of any male plants. However, male cannabis plants are important for breeding new cannabis varieties and many other things, but this is not something to necessarily be concerned with if you are a beginner.

Growing cannabis indoors can be a very fulfilling hobby, and many find gardening therapeutic as well. Growing cannabis can be expensive initially, but over the course of a year can save huge amounts of cash as you needn’t buy heavily-taxed products from a dispensary. You can grow varieties that aren’t found at your dispensary as well. Safety is another advantage, as you can be sure that harsh chemical pesticides aren’t used on your plants.

Not all states allow medical cannabis patients to grow their own, but many do. For those who are capable of growing their own cannabis, it is highly recommended that you do so, and you can get yourself a medical marijuana card to do it legally!

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Written by
Dipak Hemraj
Dipak Hemraj - Chief Research Officer

Dipak Hemraj is a published author, grower, product maker, and Leafwell’s resident cannabis expert. From botany & horticulture to culture & 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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