The basics of indoor marijuana growing
People often tend to think that indoor marijuana cultivation is something complicated and difficult that is only possible for a few connoisseurs. Nothing could be further from reality, to grow our favorite cannabis strains indoors we just need to have a few simple concepts clear and be consistent.
In this post we want to explain to you in an easy and simple way how to prepare indoor cannabis cultivation, so we will have to focus our attention on three basic aspects: ventilation, lighting and nutrition/substrate. If we keep these three elements under control and correctly choose the varieties we choose to use, indoor growing will be something simple and almost automatic, but if we neglect even one of these aspects, the yield and quality of our plants will be seriously compromised.
Throughout the post we will use the example of a growing cabinet of 1.20 x 1.20 meters in area and 2 meters in height. There are an infinite number of models of growing cabinets or growboxes on the market, so it won't be difficult to find one that is suitable for our space. Thanks to them we can better control temperature and humidity, and will thus keep our plants away from external light sources, as cannabis needs periods of uninterrupted total darkness in order to flower properly.
Summary for indoor marijuana cultivation
The main factors to consider before starting indoor cultivation are:
Lighting
Thanks to it our plants will be able to grow and bloom properly. Lighting equipment is often equipped with power supplies, reflector and lamps. Normally white light lamps with fewer watts are used for growth, while more powerful orange lamps are used during flowering.
Ballasts (ballasts) are necessary for proper lighting and lamp operation and can be electromagnetic or digital. LED, CFL and fluorescent equipment usually have the ballast incorporated in the same system, while for HPS and HM lamps it is separate.
There is also a wide range of reflectors on the market, from the simplest to air-cooled reflectors (Cool Tube). Their function is to reflect light onto plants, so the shape and material they are made of having a direct relationship with the amount and dispersion of reflected light.
Depending on the temperature and humidity in the room (even watts of the lamp), light sources are usually located 40-60 cm from the plants. It is best to measure the temperature at this height, and then raise or lower the lamp according to the temperature we need.
Growth: 18 hours of light/6 hours of darkness per day, white/blue light. Most used systems: HM, CFL, LED, Fluorescent.
Flowering: 12 hours of light/12 hours of darkness per diary, orange/red light. Most used systems: HPS, HPS+HM, LED.
Automatic Plants: 20 hours of light /4 hours of darkness per day. White light during growth, orange light when in bloom and until harvest.
Try to have the lights off during the hottest hours of the day. Use air-cooled reflectors (connected to the extractor) in case we need to lower the temperature of the room or cabinet.
Ventilation
Another key aspect of indoor growing is based on renewing the air in the box or room, as well as effective filtering that leaves the air, which comes out of the growing space, free of odors.
You can consult this handy article on how to ventilate marijuana cultivation if you need more information.
Air Extractor: Reduces heat and humidity, helps to renew the air, you can add a charcoal filter or a tubular ozonator to eliminate plant odors.
Air extractor: Must always be of lower capacity (m3/h) than the extractor. It introduces fresh air into the room/cabinet and renews it. In certain cases, you can dispense with its use and use passive suction (the extractor removes the air from the growing space, the fresh air will enter through the ventilation retinas without any need for other equipment).
Internal fan: Removes air from the growing space and prevents the formation of heat bags and stagnant air.
Usually, you keep all the ventilation equipment running while the lights are on, and at intervals set by the grower and with the help of a timer during the night phase.
Nutrition
Another fundamental aspect is based on how we feed our plants. Mainly, we have to choose between organic or hydroponic cultivation. Each technique has its own specific fertilizers and substrates that we will find in any Grow Shop.
Organic growing:
Soil to grow cannabis with a slightly acidic pH.
Solid or liquid fertilizers.
Water pH for irrigation: 6/6.8
Water temperature for irrigation: 20ºC
EC of water for irrigation: 1/1.6
Philosopher Seeds tells you in this article how he prepares his soil mix for cannabis.
I grow hydroponics:
Hydroponic substrate (coconut fiber, clay, gravel, volcanic rock, etc.) with slightly acidic pH.
Liquid fertilizers
pH of irrigation water: 5,5/6,2
Water temperature for irrigation: 20°C
EC of irrigation water: 1.2/1.8
Material needed for indoor marijuana cultivation
To start growing marijuana indoors you will need a few things, here is a list of equipment that you can't miss:
Wardrobe or grow box for growing.
Lighting equipment (ballast, reflector, and lamp).
Ventilation equipment (extractor fan, extractor fan and carbon filter to eliminate odors).
Thermo-hygrometer.
Timer for programming the photoperiod (light/dark hours) and ventilation.
Organic or hydroponic fertilizers, with the corresponding substrate.
Vases.
Seeds.
Lighting and cannabis
Normally, the first thing the grower has to decide is which light source he will use according to the space available to him. Unless this space is really too small (in which case we will use CFL or LED lamps) most growers opt for lamps that offer a better compromise between consumption/lumen, whether HM (metal halide) or HPS (high-pressure sodium).
The power and spectrum of the lamps we use will be determined by the stage the plants are at, if we need the plants to grow or flower.
During growth cannabis plants do not have a great demand for light intensity, but instead need more hours of daylight. So we will have to illuminate them for a minimum of 18 hours of light per day to ensure constant, uninterrupted growth. For this phase, the most used lights - always in the white/blue spectrum - are CFL, LED, classic fluorescent or HM lamps.
During flowering and to achieve good results in terms of yield, the plant needs a warmer spectrum, tending to red and with much more light intensity, so the most commonly used lamps for this phase are high-pressure sodium vapor lamps (HPS), on for 12 hours a day and off for the remaining 12 hours, continuously.
As we see, when we grow marijuana indoors we decide whether the plants grow (18 hours of light and 6 hours of darkness per day) or flower (12 hours of light and 12 hours of darkness per day), certainly something very convenient when we have to plan our cultivation.
Of course, this is not really the case for auto-flowering varieties like White Yoda or Cheesy Auto, which we have to grow with 20 hours of light and 4 hours of darkness per day for their whole life.
To keep the temperature as stable as possible, and to have a good ventilation system, it is recommended to turn on the lights at night, which is always the least hot time of day. If necessary, air-cooled reflectors can be used, which allow the temperature of the cabinet to be lowered by 4/6°C.
For our 3 x 3 meter grow box or a grow tent - and always looking for maximum yield - we would normally use a 400w HM lamp for growth (18/6) and a 600w HPS lamp for flowering (12/12) just as said in our other article Best 3×3 Grow Tent: Available Options and a Helpful Guide.
Ventilating a marijuana crop
With ventilation we will control the excess moisture produced by the soil and plants and also the excessive heat from the lamps.
In this way, and also taking into account that our plants need to breathe and a constant supply of CO2 and O2 into the environment, renewing the air in our growing space becomes essential, even more so if we can use air extraction equipment to eliminate the intense smell of flowering plants.
Using a simple air extractor and a vacuum cleaner (with less capacity than the former) is usually sufficient to obtain a favorable environment for our plants, with adequate temperatures and humidity levels and sufficient air exchange. Using a fan that moves the air in the growing space is also recommended so that the formation of heat bags of consumed air is avoided. To eliminate odors from cultivation, simply connect a carbon filter - or tubular ozonator - with the air extractor so that it can filter before ejecting from the cabinet/room.
Generally, the plants develop better with temperatures near 20°C when the light is off and around 26/28°C when the light is on. The relative humidity should be 60/70% during the growth phase and about 50% during flowering. Most growers use thermo-hygrometers with minimum/maximum readings to monitor these values and timers to turn the ventilation on and off according to these readings, although it is possible to use climate control units that automatically turn the ventilation equipment on and off according to the parameters we have decided to set.
As you can imagine the power of our ventilation equipment will have to be in accordance with the volume of the growing space and the type and power of the light sources, part of its function is to eliminate the heat emitted by the lamps and therefore it must not only be able to renew the air in the environment in which we grow in a few minutes.
For our example, the 1.20 x 1.20 meter cabinet with 400w HM lamp in vegetative phase and 600w HPS during flowering, will be enough for us, with a tubular extractor (type RVK or PK) of 125mm diameter, an in-line extractor fan of 100mm and a gripper fan of 15cm diameter.
Nutrition and substrates for marijuana plants
We have the lighting equipment that best suits our growing space, and we have chosen appropriate ventilation for it. It remains for us to decide what kind of cultivation we want to achieve. Even though there is an infinite number of techniques and systems, we start with the basics, organic cultivation, because this type of cultivation allows more mistakes by new growers and, in our opinion, offers better quality.
To make an organic crop we have several options: buy lightly fertilized soil - type Light Mix - to which we have to add liquid or solid nutrients within a few weeks (2/3) or buy fertilized soil - type All Mix - to which for a few months (2/3) we only have to add nutrients during cultivation, such as stimulators or enhancers.
Remember that you need to irrigate when the soil is still slightly moist, but not wet, and use fertilizers in line with the stage in which the plant is growing or flowering. To learn more about this topic we recommend reading the post on how to irrigate marijuana in soil.
In case we need to use extra nutrients in addition to those already in the soil, we can opt for solid fertilizers, which can be mixed with the substrate when we prepare it to fill the pots and work wonderfully in guerrilla gardening crops and with automatic plants, or liquid fertilizers, which we should use in moderate amounts every time we irrigate, perfect for varieties with moderately long flowering, such as Fruity Jack / Jack El Frutero or SuperJuani. In any case, the water temperature for irrigation should be about 20°C, with a pH of 6.5. If we use liquid fertilizers and have a doser, we have to correct the EC to 1/1.2 during the vegetative phase and to 1.4/1.6 during the flowering phase.
Growing marijuana
Once we have clear and mounted the cabinet with the ventilation and lighting equipment, we can already fill the pots with good soil, water moderately and sow our marijuana seeds. With a photoperiod of 18 hours of light and 6 hours of darkness per day, we will let our plants grow for 2/4 weeks, depending on the variety: 2/3 weeks for Sativa varieties; 3/4 weeks for Indices like Black Bomb or Tropimango.
When you get to a suitable height, we will change the photoperiod to 12/12, when the plants will start flowering. If we have enough space we can transplant them into a larger pot at this stage, we also recommend changing the growth fertilizer with the flowering fertilizer.
A couple of weeks before harvesting we will stop fertilizing the plants, irrigating only with water until the end.
We hope that with these tips you will have the courage to grow indoors. When you try the unbeatable taste of your flowers you will realize that it will be worth all these efforts.
Just like indoor cultivation, there is nothing.
Have a good cultivation!