Whatever the motivation is, to grow cannabis indoors, we must consider that there are outdoor and indoor varieties when choosing the seeds to plant.

Outdoor plants, even of great quality, would need an adaptation to the artificial environment that requires generations of selected seeds to achieve good results.

Especially in the Netherlands, this has been done for years, so much so that in recent years there is a great number of seeds of guaranteed quality for all types of crops. 

The genetics of a seed is the most important factor determining the quality of the final product. A genetically “poor” seed, even in the best conditions, will still give a modest result in terms of the specific quality of the resin produced.

Hemp has two main phases in its life,the vegetative and the flowering. Flowering begins when the plant perceives that the length of the period of sunlight is shortening, indicating the approach of autumn which coincides with the end of its life cycle. When the day begins to be shorter than the night, plants will start flowering regardless of the size reached.

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Growing indoors, flowering can be forced through exposure to artificial light. The grower replace mother nature and can decide when the ideal time has come for their plants to bloom.

Sunlight has a lot of ultraviolet rays that would burn an indoor grown plant that has grown with artificial light, if suddenly moved outside. In case you wish or have to kove your plants outside, consider the adaptation will have to take place gradually.

Indoor cannabis grow using HPS lamp

It is advisable to improvise a small greenhouse that can partially shelter the plants from direct sunlight, especially during the hottest hours. Both indoor and outdoor cultivation can give excellent results. In the first tho, the grower has greater control, expenses and the ability to grow all year round regardless of the seasons.

Outdoor growing surely has  an economic advantage due to lower costs, especially for electricity and equipment. The harvest is limited to a single annual cycle and the plants are in fact exposed to bad weather and parasites that are hardly present when growing indoors.


Fluorescent lights have been used for growing indoor plants for many years.

Since the advent of high-pressure lamps: sodium vapor (HPS) and metal halide (MH) lamps; other lamps have become obsolete, with the exception of fluorescent ones which continue to be used successfully, together with full spectrum LED lights that continue to evolve.KIND LED K3 Series 2 – XL300 Grow Light

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MH (metal halide) bulbs, such as cool white and gro-luxe type fluorescent lamps, are ideal for vegetative growth and are suitable for germination and cloning of young cuttings, as they emit a generally white light. 

Many growers choose full spectrum LED lights that emit a wide variety of light spectra and suitable for all stages of growth, with the advantage of being quiet and hardly emitting heat.

HPS bulbs, on the other hand, are ideal for flowering and suitable for growth as they emit spectra of warm light with colors ranging from amber to orange, therefore similar to the natural light typical of the months towards the end of summer.

High pressure lamps are delicate and heavy, so they must be firmly fixed with chains or pulleys, also because the light will have to rise as the plants grow. They also need a ballast in order to function.


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When using fluorescent lights we have to think that blue or cold is more suitable for growth and red or heat is more suitable for flowering. The recommended distances from the light to the tips of the plants depend on the type and power of the lamp. For example, when using fluorescent lamps, the distance from the tops of plants can be minimal as they generate very little heat.

The distance for a 400 W HPS bulb, for example, must be kept during the cycle at least 50cm away from the tops of the plants. This results in the need to often adjust the height of the lights as the tops of the plants grow to avoid burning them.

The light requirement of marijuana is between 10,000 and 30,000 lumens per square meter.



Anything that is used as growing media and substrate must be sterilized. Soil mixes for indoor cultivation are usually sterilized, alternatively you can make your own mix.


CANNA Coco 50L Bag

CANNA Coco substrate is a 100% natural organic media substrate NOT STEAMED  made from coconuts grown from coconut in Sri Lanka. It has a fine texture, uniform structure, free from viruses, chemical additives and soil diseases

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The fundamental characteristics of the materials to keep in mind are the water retention capacity, and the capacity to drain. The ideal growing medium is composed of a mix that optimally combines these two elements.

In hydroponic farming the substrates used are inorganic and devoid of nutrients, as these are diluted in water. In traditional crops, on the other hand, non-sterile organic materials are used such as peat, earthworm humus, manure, manure and compost. All these elements can carry fungal spores, larvae and parasite eggs.

Many of the inorganic materials used, on the other hand, don’t contain any nutrients. They were originally conceived as insulators for the industry and only later were they introduced in gardening due to their characteristics.

Here are some of the most common:

Perlite: expanded glass, forms small white granules, which crumble when pressed. Very light and draining material. In addition, it provides good ventilation.

Vermiculite: Holds water in its fibers in large quantities while allowing good ventilation. It is very light but does not allow excellent drainage. It is generally marketed in three sizes, the finest being used for germination and cloning as the main substrate. Thicker vermiculite is used in blends.

Expanded clay aggregate: Allows for great aeration and good drainage, while retaining some moisture. It is used in mixtures and as a draining bottom in pots.Mother Earth Hydroton Original 50 L expanded clay lightweight aggregate

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Volcanic stone: has the same characteristics as expanded clay, but has a higher specific weight. It can hold more moisture as its surface is more porous.

Coarse sand: the type used in gardening, aquariums, or even the type used in construction, even if it needs to be washed. It has the same characteristics as vermiculite but with greater drainage and weight.

Rockwool: it is also a thermal and acoustic insulator. It retains water and allows for good aeration which makes it a good means of germination. Rock wool tends to basify the water, so it is convenient to water with a low pH to balance. It is a very practical and relatively inexpensive medium, as well as being reusable.

The mixtures proposed below contain between 40-50% organic matter and 50-60% inorganic. Inorganic materials are recyclable as are mixtures if cleaned from the roots and integrated with new organic matter.

  • 3 parts of humus and peat
  • 2 parts of perlite and/or clay
  • 1 part of vermiculite  and/or  sand

Other mixes could be peat-perlite or peat-clay expanded at 50%, alternatively humus-peat could be used or all four could be combined in equal parts. In short, each mix must comply with the aforementioned criteria. There are on the market already sterilized and ready to use.


In nature plants have no space limits for growing their roots. By growing indoors in pots we will limit the growth to the size of the containers we choose. Furthermore, each transplant traumatizes the plant slowing its growth.



Smart Pots w/ Handle

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We must consider the dimensions of the containers in relation to the space available, then find the right compromise. I would say that the minimum capacity of a container must be at least 8-12 liters (2-3 gal), going for the largest size when possible.

When growing in a grow box we will have to move and turn the plants on themselves to allow uniform growth, so the materials used must be as light as possible.


It is important to know the atmospheric conditions we want to create when it comes to choosing the ideal mounting location. Cannabis plants are able to withstand temperatures between 10 and 40 ° C. The temperature should however be maintained between 18 and 30 ° C as much as possible.


ExHale Original Homegrown CO2 Bag

Exhale CO2 Cultivating Bag for Indoor Grow Rooms  provide a continuous supply of carbon dioxide with no need to refill bottles or use expensive regulators, generators and monitors. The power of the product lies in the mycelial mass, which is growing on organic matter inside the cultivator, and the one-way breather patch located on the bag

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Hemp is capable of absorbing carbon dioxide (CO2) from the air in a much higher concentration than is found in the atmosphere. Plants grow faster by increasing their concentration.

Excellent results can be obtained without overly complicating your systems simply by allowing fresh air to enter the system from the outside which will provide the required CO2. Air must be moved through a fan inside the system. The system will therefore need an air intake, and an air extractor to the outside of the grow room.


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In short, it’s fundamental that air circulates, fans will only work when the light is on.

Humidity levels should remain between 40 and 60% and can be monitored together with the temperature using a thermometer-hygrometer.

The size of the system depends on many factors, on the plants we intend to grow and must be reflected in the power of the lights available. Furthermore, make sure to not place the system near other plants e and vegetation that could introduce parasites. A complete darkness need be maintained inside the system during the “night” cycle.


Hemp needs plenty of water throughout the process, especially during the vegetative growth. If you use tap water is a good idea to let it “sit” for a day before using it to water your plants, so that the chlorine can evaporate.

The pH of the water should preferably be neutral or slightly acidic. An optimal pH is between 6,5 and 7,2The pH has a scale from 1 to 12 where 7 represents the neutral pH, 1 the most acidic and 12 the most basic / alkaline. It is important to measure periodically the pH of water and soil by mixing them together. Values ​​far from those above can compromise the good development of the plants.


HM Digital Waterproof pH Meter Model PH-200 measures pH and Temperature 

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There are several methods of measuring pH that don’t cost much, but offer a very must have tool. An excessively acidic pH can be corrected by adding hydrated lime or bicarbonate. A very high pH can be corrected by adding nitric acid, or simply vinegar or lemon. In addition to these method to correct the pH there are commercial grade professional products available as these below that can be used with much ease.



DaKine 420 pH Down

If your Ph is getting too high, the best strategy is to bail out and drop down, Point Break style!

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Regarding irrigation, we know that water within the system will evaporate in part due to the heat generated by the lamps. Plants have to pass short periods of “drought” between one irrigation and the next. It’s always better to wait until the soil on the surface and a couple of centimeters down is dry before watering again. Plants would end up rotting if the watering is excessive, on the contrary we will notice the lower leaves drying up.

In other articles we talk more in detail about the nutritional needs of cannabis plants, the most common parasites and the most frequent problems caused by nutritional deficiencies and wrong conditions within the system.

Happy grow everyone!