Grow Light Buying Guide for Cannabis Cultivators

Farmers have been cultivating and growing crops for thousands of years using the natural light of our sun, which happens to be composed of all the wavelengths needed to support life on earth.

Plants (except fungi) especially need plenty of light to thrive. However, plants tend to be particular with which wavelengths they absorb for photosynthesis. But what is light? And why is it important for cultivators to understand the impact of different wavelengths on their plants when shopping for grow lights?

Light is a Form of Radiation

First, before we start throwing the term “radiation” around, it’s important to mention that there are two types of radiation. Nuclear radiation consists of particles such as protons and neutrons. Electromagnetic radiation (EM) consists of packets of energy called “photons.”

Electromagnetic radiation refers to packets of energy called photons, whereas nuclear radiation usually refers to protons, neutrons, and particles with mass.

As we discuss light as a form of radiation in this article, we will be referring to “electromagnetic” radiation, often considered to be pure energy (it has no mass.)

Riding the Wave to Visible Light

There are many types of EM radiation, and you are probably familiar with most of them! Shorter wavelengths include gamma rays and x-rays. These shorter wavelengths contain higher amounts of energy and are harmful to living cells.

Spectrums of Light
Electromagnetic radiation we consider to be within the “Visible Light Spectrum,” is also used by plants for photosynthesis.

Longer wavelengths consist of radio waves and the infrared light your remote control uses to communicate with your TV. Although generally considered safer than short wavelengths, with enough energy behind it, longer wavelengths of EM radiation can be dangerous as well. As they say, all things in moderation.

Photosynthetic Active Radiation (PAR)

Now that we’ve established that we interact with radiation every day, let’s take a look at the type of radiation we’re all most familiar with. Visible light is electromagnetic radiation that falls between 400 and 700 nanometers (nm.) This can vary from person to person, but generally speaking, these are the wavelengths we can see with our naked eye.

Photosynthesis Formula
Plants use light that falls within the PAR spectrum to conduct photosynthesis, converting carbon dioxide and water into oxygen and glucose.

It’s no coincidence that our botanical friends also require visible light to perform photosynthesis for energy. Cannabis and humans have grown and adapted on this planet together. And just as we utilize visible light more than any other forms of EM radiation, so it is with plants. Botanists call this EM range, “Photosynthetic Active Radiation” – or PAR for short.

Grow Lamps vs. Natural Light

While shopping for grow lights for your new cultivation operation or expanded greenhouse, you want to purchase grow lamps that can support both the vegetative and flowering cycles of your cannabis plants. Most commercial grow lights will detail which wavelengths of PAR they emit so you can match the best light for your plant’s development.

Although natural light provides the most diverse range of light for plants to grow and mature, meeting health and safety requirements means growing cannabis in closed-system environments. This helps mitigate mold, mildew, insects and other contaminants.

As such, engineers continue to develop more sophisticated grow lamps to produce the essential spectrums of light cannabis plants need to thrive. Next, let’s take a look at the various types of grow lights available to cultivators.

HID – High Intensity Discharge Lamps

HID grow lights, short for “High Intensity Discharge” lamps, are the go-to and staple of grow lighting for cannabis cultivation. They are one of the most cost-effective lighting solutions for new build greenhouses.

High Intensity Discharge Grow Lights
High Intensity Discharge or HID lamps, require a lot more energy than LEDs, however the bright, intense light emitted is great for covering a large crop of cannabis plants.

HID grow lights can be used for all stages in the cannabis plant’s growth cycle, depending on which type of gas the lamp contains. HID includes many popular lighting options, and three of the most popular are Metal Halide (MH), Ceramic Metal Halide (CMH), and High Pressure Sodium (HPS.)

MH – Metal Halide

Metal Halide lamps fall within the family of HID lighting. They generate intense light by channeling electricity through an arc-tube, literally creating an arc of electricity through a desired gas.

Metal Halide Grow Lamp
Metal Halide or MH lamps are high powered HID lights that emit a blue spectrum of light that supports healthy vegetative growth.

The resulting EM radiation produced by MH lamps favors the blue spectrum of light, which is extremely important to the vegetative growth cycle.

HPS – High Pressure Sodium

High pressure sodium grow lights, like metal halide, are part of the HID family of lamps. HPS grow lamps utilize mostly sodium, which produces a warmer spectrum of orange-red light.

High Pressure Sodium Grow Lights
High Pressure Sodium or HPS lamps are high intensity lights that favor warmer spectrums of light that enable the cannabis plant to develop strong buds and more trichomes.

HPS grow lamps activate hormones within the cannabis plant and encourages the strong development of cannabis buds. Building HPS lamps into your lighting rig can help your premium cannabis plants grow larger buds and more flower.

CMH – Ceramic Metal Halide

Another type of popular grow light is the ceramic metal halide lamp. CMH lights also fall into the High Intensity Discharge (HID) lamp family. This type of grow light offers the intensity cultivators expect from HID lamps, however they excel where other types of HID lamps fall short.

Ceramic metal halide grow lights use ceramic arc tubes that are far more durable than the materials built into other HID lamps. This results in increased durability, lasting more than twice as long as High Pressure Sodium and Metal Halide lamps.

Ceramic Metal Halide Grow Lamp
Ceramic metal halide or CMH/LEC lamps often cost more up front. However, they provide a balanced spectrum of light that can eliminate the need to alternate HID grow lights based on the plant’s stage of development.

Most importantly, Ceramic Metal Halide grow lamps convert more electricity into the photosynthetic active radiation cannabis plants need to thrive. By converting more energy into PAR, there is less wasted light. With its many advantages over other HID lights, CMH continues to grow in popularity among cannabis and hemp cultivators.

GDT – Gas Discharge Tube (Fluorescent)

Fluorescent lighting has been around almost as long as incandescent lamps. Due to incandescent lights being simpler to manufacture, they became the mainstay for decades while fluorescent lighting evolved more slowly.

The great-grandfather of the fluorescent lamp is the Geissler Tube, which was invented by a German physicist named – you guessed it, Heinrich. However, the invention of the modern fluorescent light is attributed to scientists at General Electric in 1934.

Fluorescent T5 Grow Lamp
Fluorescent lights or gas discharge tubes require ballasts, however they consume far less electricity than HID lamps. T5 fluorescent lights also offer a balanced spectrum of light for your cannabis or hemp crop.

Fluorescent lights are known for having a longer life than HID lamps and are less expensive to replace. They also emit less heat, making it easier to maintain optimal temperatures in your grow room.

LED – Light Emitting Diode

Cultivators have favored HID grow lamps over LED’s for a long time, and with good reason. HID lighting has been traditionally brighter, providing more light to plants. However, LED grow light technology has made technological leaps over the years.

LED Grow Lamps
Light Emitting Diode or LED grow lights are quickly becoming the premium choice for cultivators. LEDs run cool, offer customizable light spectrum output, and last far longer than any other type of grow light.

More farmers are taking advantage of the positive benefits of modern, LED grow lamps. LED lights offer all the benefits of fluorescent lights while mitigating some of the challenges.

Although LED grow lights are usually much more expensive than HID and Fluorescent lamps, their benefits easily make up for the cost. As a matter of fact, most cultivators actually save money in the long run due to the following advantages:

  • LEDs emit far less heat than HIDs, and even less heat than fluorescent lamps. This saves money in electricity and cooling costs.
  • You can use the same LED light for all stages of cannabis development. An LED grow light can be configured and optimized for vegetative or flowering cycles.
  • Light emitting diodes last tens of thousands of hours, far more than HID lights and even fluorescents.
  • Utility savings, durability, and longevity make LEDs more cost effective than other grow lights as long as a cultivator can afford the upfront investment.
The Gavita Pro 1700e LED in action.

Choose Your Lights and Get Growing!

Whichever type of grow lights you choose to build into your greenhouse or grow room, it’s important to understand your horticulture goals. If you have a crop of cloned strains, then you may prefer cooler, blue light to help support their structural, vegetative growth.

If you have a mature crop of cannabis plants, then showering them with warmer grow lights will facilitate larger, trichome covered buds and flowers.

And don’t forget to consider your location and electricity budget. LEDs and Fluorescent lights are great for conserving energy, whereas the HID family of lights are intense and great for those with lower power restrictions.

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