How to Grow Cannabis with LED Lights

In recent years, LED lights have completely revolutionized indoor cannabis growing. They have proved themselves to be the most affordable, effective, and technologically advanced option when compared to other lights. This article will get into the specifics of why these are the industry standard and what everyday growers can do to get the best results at home. 

Intro to LEDs 

Light-emitting diode lights (LEDs) utilize fast-moving electrons to created photons inside a semiconductor where pure light is produced. In contrast, incandescent light bulbs produce heat and light, making them less energy-efficient. In fact, the difference is staggering: LEDs use about 75% less energy than incandescents. They’re also a bit more efficient than compact fluorescent lamps (CLFs), which use about 5% more energy than LEDs. 

High-intensity discharge (HID) was more popular at one point, but growers realized that ballasts- devices for managing electrical circuits- lost efficiency over time and required replacements. HID also releases materials like mercury and other harmful gases, so LEDs naturally became the simpler, cheaper, and safer option for cultivators everywhere. Here are the pros of LEDs summarized:

  • No extra heat created 
  • Less heat means less watering 
  • 50% less energy required than HID, 75% less than incandescent lights
  • More concentrated light 
  • Up to 50,000 hours of use 
  • No harmful materials released 
  • If your plants need more light, it’s an easy adjustment!

The Main Types of LEDs

For cannabis, only red and blue light is absolutely necessary; these colors are made of wavelengths that benefit the plant the most. “White” LED light can be used as well, but only if it’s intended to be used for growing and has emphasized reds and blues in its spectrum. 

Grow light LEDs have adjustable hues so that the grower can manipulate the colors; more blue is needed more in the beginning stages, whereas red helps facilitate healthy flowering. There are three main types of LEDs used for marijuana growing:

  • Standard LED. These “purple” lights are made of hundreds of red and blue LEDs and are very affordable and widely available. The downside is that may result in lower flower yields. 
  • COB LED. “Chip on boards” (COBs) have hundreds of LEDs on a single chip, making the light more concentrated. They’re a bit pricier, but many can be fine-tuned to your plant’s light spectrum needs. These can be used in large spaces, too. 
  • Spread-Style LED. These have tiny LEDs comprised on a board, rack, or panel. They can be incredibly expensive but are most used in commercial spaces. 

A good rule of thumb is for every 1 or 2 individual plants, you’ll need one 75 watts LED lamp. 

Seedling Stage 

Your plant will need much dimmer lighting when it’s a seedling. Try keeping your LEDs a bit farther away, but not too much distance. You should place the light about 50-60 cm away from the seedlings and close the distance 2-3 cm each day and pay close attention to the plant’s health. If your LED has a “vegetation” and “flowering” setting, set it to “vegetation” so that more bluish rays are emitted. Seedlings need 18 hours of light per day and 6 hours of total darkness. As the plant grows, increase the light intensity gradually; though, if it looks thin and weak, it’s not getting enough light. If its leaves begin to brown, it may be too intense.

Vegetation Stage

When your plant reaches vegetation- meaning that it grows bushier and fuller- you can slowly increase the bluish LEDs and keep it on for 18-24 hours per day. Keep in mind that the more light you use, the more it will grow, so take into consideration the amount of space you have available. It’s recommended that you research the growing patterns of various strains since some will stretch more than others before being able to flower.  

Flowering Stage

Cannabis flowers in the late summer, but as an indoor grower, you’ll need to recreate this with more red light or with a “flowering” setting on your product. The plant will need only 12 hours of light and 12 hours of total darkness. Make sure that there is absolutely no light entering the room or greenhouse during the dark period- it can disrupt the flowering stage. 

If your weed is an autoflower- a type of cannabis that flowers based on age rather than light availability- then you can keep your lights on for up to 24 hours. 

Is Full Spectrum Worth it?

Most growers will insist that full spectrum is the best, but this is a myth and the term is used as a marketing tactic. Plants only utilize PAR light (photosynthetically active radiation) to live, which consists of wavelengths between 400 and 700 nanometers. “Full spectrum” products imply that they can recreate the infrared and ultraviolet rays of the sun, but no LED is able to do that. 

Instead, invest in narrow spectrum, which can reliably produce red or blue light, or broad-spectrum, which may appear to be “white”, but is really producing variations of red, green, and blue together. 

Lighting is just one part of the equation when it comes to cultivating weed. Paying close attention to your plants’ nutritional requirements alongside proper LEDs is sure to get you the quality yields you’re looking for!

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Costanza Kelley

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