There are many benefits to growing your own cannabis indoors, but the only way to get the best crop is by understanding the different light cycles involved in the cultivation process. It is therefore vital to choose the type of lamp that best suits every phase of growth.
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Are you planning to grow indoors? If so, it’s important that you understand the different light cycles of cannabis plants. And the basis for success is imitating the natural light pattern that plants would be exposed to should they be growing outdoors.
The growth or vegetative phase is a crucial time since this is when the stems and leaves start to grow. It is during this stage, when cannabis plants don’t produce any flowers, that you need to control their shape and size. This is where the light cycle comes in: the more light your plants receive, the better they’ll grow, which will lead to better yields.
During the vegetative phase, it is advisable to provide the plants with at least 18 hours of light per day (this is also known as the 18/6 photoperiod). Cannabis plants don’t start developing flowers until they are exposed to 12 hours of uninterrupted darkness. Failing this, the plants will remain in vegetative mode.
As long as your plants are exposed to a minimum of 13 hours of light per day, they’ll remain in this vegetative phase. But if you’re a producer eager to grow your plants as large as possible, you can even expose them to indoor lighting for 24 hours (24/0). Generally speaking, though, most growers opt for an 18/6 indoor vegetative period for 4-8 weeks (around 60 days).
Indoor cannabis at the blooming stage
Cannabis plants that grow naturally in the open air start developing flowers as the days become shorter. This is why most indoor growers change the photoperiod to 12 hours of darkness immediately after the plants have reached the desired size and shape during their vegetative phase.
Cannabis plants don’t grow as much during the flowering phase, although they can potentially double their size and height. You need to make sure that your plants are NOT subjected to any type of lighting during the 12 hours that they’re meant to be in the dark. Even a pilot light or street or home lighting can be enough to seriously hinder your plants’ flowering period.
Once plants shift to the flowering photoperiod (12/12), you normally need to wait for 10 weeks (2 and a half months on average) before the buds are ready for harvest. Some indica strains flower more quickly (in around 60-70 days), whereas some sativa varieties take longer (80-90 days).
Which type of lighting do I need to use?
The first thing you need to find out before choosing a lamp is what’s the best light spectrum for your plants. In order to recreate what happens in nature, cannabis plants basically need a blue light spectrum during growth and a red light spectrum during blooming. The green spectrum doesn’t affect them, so if you want to use light in your grow that doesn’t alter the photoperiod, this kind of lamp is the most suitable for you (for instance, if you need to work in your grow while the plants are meant to be in the dark).
HID (high-intensity discharge) lamps are one of the most commonly used in indoor cannabis growing. There are two main types within this category: MH (metal-halide) and HPS (high-pressure sodium) lamps.
The difference between these two types of lamps is that MH provide a cold, blueish light, whereas HPS lamps are reddish and therefore warmer. This is why MH lighting is recommended for the vegetative phase, and HPS is better suited to the flowering phase. If you can only choose a type of lighting, best to use HPS with dual spectrum for both phases of growth.
HPS lamps are renowned for their high performance, but they generate a lot of heat, so you might need to install a ventilation system to help with this. In addition, all HID lamps degrade with time. HM lights degrade more quickly than HPS, but both need to be replaced after several harvests. Most reputed brands (Philips, Lumatek, Osram, and Sylvania) offer models adapted to each stage of growth, but they also include mixed types, which are dual spectrum HPS lamps that are valid for both the vegetative and the flowering periods. These are an example:
LEC lighting, the next frontier
LEC or CMH (Ceramic Metal Halide) are an evolved version of the sodium lamps. Nowadays LECs are the lamps that most closely resemble the spectrometry range produced by natural sunlight, which in turn translates into better results. In addition, LEC lamps also emit less heat.
Thanks to the great quality of the spectrum produced by LEC lighting systems, you can obtain better gram/watt ratios and greater production and preservation of terpenes.
All the LEC lamps currently on the market are suitable for both the vegetative and the flowering phase. However, those with a colour temperature of 3100K are more appropriate for short-flowering cannabis. On the contrary, CMH or LEC lamps of 4200K, or more, are better suited to sativa-dominant or long-flowering strains. Here you can find a wide selection of the LEC lamps currently available on the market:
And how about LEDs?
LED lamps have been quickly gaining ground of late, partly due to their reduced electricity consumption and low heat emission. The initial investment is much higher, but they are more energy-saving in the long run, as well as having a longer working life. You can use a full spectrum LED lamp for both the vegetative and the flowering phase, or you can get panels with different powers and spectrums that can be configured according to the different phases. Some LEDs even include infrared and UVB spectrums, which helps generate trichomes and thereby achieves a higher-quality cannabis.