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cannabis e luce: sole o lampada da coltivazione indoor

Cannabis & Light: Better Sunlight or Indoor Growlamp?

Cannabis & Light: Sunlight or grow-lamp in Indoor growing

In the cultivation of Cannabis, whether for recreational-therapeutic or commercial purposes, light is a parameter that plays a fundamental factor in the development of the plant! In this chapter we will discover together the main differences between sunlight and Indoor lamps, and which are the most suitable lights in the Germination, Vegetative and Flowering phase of Cannabis!

Sunlight in Cannabis grow:

After several decades spent using the most diverse indoor cultivation techniques, from the most “oldschool” to the most complex and innovative ones, the cannabis community has not yet managed to match the quality of sunlight. It still remains the best light for the complete photosynthesis process of Cannabis plants. This because Cannabis is a photoperiod plant, meaning it blooms according to the hours of light it receives. Marijuana plant requires powerful light to produce the beloved quality buds.

However, Cannabis Ruderalis is an exception to the photoperiod cycle: a distant cousin of Cannabis Indica and Sativa, discovered many years ago in cold areas such as Russia and Siberia. We will talk about the various types of Cannabis later, for the moment it will be enough for you to know that it is the only cannabis variety that blooms regardless of the amount of light administered, but producing thin flowers and with a lower percentage of cannabinoids and essential oils, such as terpenes and flavonoids.

If it is therefore true that the sun is the best lamp we could ever afford, it is equally true that the sunlight cannot be decomposed from the rest of the climatic factors, unpredictable and often catastrophic. Furthermore, in many northern European countries the hours of sunshine are not sufficient to sustain a satisfactory harvest.

Over the years, therefore, the need arises to be able to cultivate in a safe and controlled space in its environment. A closed environment that can guarantee a conspicuous production in front of invested resources (such as time and money), and that can prevent possible climatic catastrophes by allowing you to set every environmental parameter: Indoor Cultivation.

cannabis e light indoor growlamp or sunlight

Indoor Grow Light (Growlamp):

Growing Cannabis indoors will involve buying a growlight. Nowadays it is possible to easily buy different types of indoor growlamps, from the least expensive to the most efficient: the final choice will depend solely on the needs of the grower, as not all lamps are suitable for various cannabis developments. Follow us in the next articles to find out every detail on the various grow lamps on the market.

Now let’s see together which lamps and which spectra are the most suitable for indoor cultivation, listing them according to the different stages of development of the Cannabis plant:

Lights for Cannabis Germination stage:

In germination stage of Cannabis plant, a low energy consumption lamp is indicated, such as a neon or a low energy consumption lamp (CFL), possibly with a white spectrum (frequency K 6400). This is because the Cannabis seedling will initially be involved in the development of the root system. In fact, in this first stage the plants will not yet have leaves useful to initiate chlorophyll photosynthesis.

The light should not be too strong, but sufficient enough to deliver a good amount of Lumen. It must be close enough to the plants not to induce them to “stretch” (a word that in growers’ jargon expresses the dangerous lengthening of the stem of cannabis plants) due to the search for light.

Annibale’s Team suggests for a cultivation area of:

It is recommended to keep the growlamps at a height greater than 10 cm from the ends of the lamps. In this stage, the young plants can easily suffer of heat burn.

In this first phase, the light cycle can vary from 16 hours of light and 8 hours of dark up to 24 hours a day of light. We recommend a cycle of 22/2 only for the first phase of germination (thus avoiding the risk stretching). See more about Cannabis Germination in this article!

Cannabis Lights for Vegetative Cannabis Phase:

When the plants have reached the fourth stage of leaves in the vegetative stage of Cannabis plant, can be noted that they will begin quickly to grow. From now they develop, in addition to new young leaves, also the first young lateral branches. It is recommended to change the growlamp or increase the amount of light, as the vegetative phase has entered.

With an 18/6 (or 20/4) light cycle, the lamps we indicate in the important vegetative phase are:

  • 60x60cm = 1+ 300w CFL Lamp;
  • 100x100cm+ = 1 MH Lamp (Metal Halide) or 1 CMH Lamp (Ceramic Metal Halide) with respectively 400/600w and 315w.
  • 1 LED Lamp, scrupulously following the manufacturer’s instructions, and being very careful to respect adequate safety distances.

A MH o CMH  lamp (spectrum K 6400) is what we recommend for an optimal development of the root system, new leaves and new sites (branches).

The safety distance for Cannabis growlamp is from 40 cm to 60-70 cm from the apex of the plants. Exact misure depending on the extraction system, and on the power of the lamp itself (and therefore, on dispersed heat).

To be sure of the height of the lamp, stretch the back of your hand to the height of the apex of the plants, and if after fifteen seconds you do not feel particular heat it will be fine.

cannabis e light indoor growlamp or sunlight

Cannabis Lights for Flowering Phase:

After weeks of vegetation, the plants have grown large enough to occupy the grow space (¾ for a S.O.G grow). Now, you have to change the light cycle (Switching) from 18/6 (light / dark) or 20/4 to 12/12. By doing so, the plants will enter the flowering phase! You will be able to see the first flowers around the second week after the change of light hours. If you are growing regular cannabis seeds, it is time to separate the males from the females. Transfer males before they can pollinate the female, dramatically lowering the final quality of the Marijuana crop.

In this phase the plants will tend to stretch very quickly, reaching even 5 times the height they had before the change of light hours. Be careful not to take too long to let the flowering plants pass or they will grow real giants. Skip to the next paragraph until day 25 of flowering to keep the plants lower.

During flowering you will have to change the lamp and switch to the famous HPS lamp, or CMH. You can also opt for an LED lamp.We believe that CMH and HPS is the most suitable for this phase. Just believe that HPS are still the most used lamps in the world by indoor cannabis growers!

Ensure the right amount of light to high peaks as well as to lower sites and in dim light. To do this, we recommend techniques of Summary Defoliation and Lollipop. These techniques encourage the Cannabis plant to develop tall, large and compact flowers. This will avoid the uncomfortable “Popcorn Buds“! See more about flowering stage of Cannabis plant!

Cannabis Grow-lamp Tips

Be sure to adequately extract the stale air from the grow area by ventilating and exchanging the air using a Clip Fan!

High temperatures (28 ° +) can degrade cannabinoids and volatile compounds, such as terpenes and flavenoids. In fact, heat can inhibit the development of flowers and leaves, and in the worst cases suffocate the Cannabis plants.

If the grow lamps have even minimal trauma or scratches to the protective glass visible, never use them! Try to avoid accidents that could draw the neighborhood’s attention to you.

Avoid poor material or the carelessness of isolating electrical sources from water sources, principal causes of fires. Never work with poor quality materials or materials of unknown origin.

See you in next articles about “How to Grow Cannabis Plants“, greetings from Annibale’s Team!


Davide, CEO Founder & Geneticist