LED has been innovating the cannabis growing community, HID (high intensity discharge) remains fixed in old technology, and the old problems that accompany them. 

The multiple parts and pieces that make up an HID system provide ample opportunity for bugs, dirt, bacteria, mold, and fungal spores to hide. High temperatures and long cool down times elongate the laborious process of cleaning, and make maintaining hospitable temperatures a hassle. The HVAC system required to combat the heat radiating off of these fixtures is enough to bankrupt new growers in over their heads.

HID lights require a “warm-up” period because the lighting intensity changes as the material inside the bulb is evaporated into plasma. As the light heats up it requires additional voltage to operate. Over time, HIDs require more and more voltage to produce the same amount of light until eventually the voltage exceeds the fixed resistance provided by the ballast and the light burns out. HID lights become less and less efficient over time because they must use more and more voltage to produce the same PPF output as the light degrades.

HID lights are also omni directional, so about 50% of its output must be redirected in order for crops to receive the output guaranteed by the bulb manufacturer. But worst of all, HID lights harbor an invisible menace. One that ravages leaves, stresses plants, and lowers crop quality. Infrared Radiation.

What is Infrared Radiation and where does it come from?

Infrared radiation is a high wavelength portion of the light spectrum, just above the visible spectrum. Essentially, infrared is heat, beamed from certain light sources, like the sun, onto the surface of whatever their light reaches, warming whatever they touch. Heat radiates off of everyone, and all objects are constantly losing and exchanging heat in a process known as entropy. However, with infrared radiation, the emitter does not need to be in close proximity in order to radiate heat towards whatever is in its path. It can be done across large distances.

HID lamps produce light by sending an electrical charge or “arc” between two tungsten electrical conductors and through an ionized gas (plasma) housed inside the bulb. As the plasma burns it emits light and infrared radiation. Roughly 30% of the energy HID lamps use goes to make infrared radiation, which is then beamed directly onto the surface of the plants that the fixture is mounted above.

Infrared In The Grow Room

While outdoor grows can do well under the natural infrared beaming from the sun, indoor grows are seemingly more precarious. Grow rooms are balancing acts where every one of the 9 parameters for plant growth must first be created before they can be managed and tweaked to drive photosynthesis in the plant and create larger yields. While an outdoor climate might naturally sit around 75º and bring natural breezes, indoors, air currents must be introduced in a grow room and temperature controlled.

Under infrared light, the temperature of a crop’s leaf surface is much higher than the ambient air temperature. Plants perform photosynthesis best at a specific range. For cannabis, this range sits at around 77-86º fahrenheit. Any colder, and the plants will close their stomata, truncating their ability to perform transpiration, causing them to take on mass more slowly. Any hotter and the plants may enter photorespiration, burning more carbon than they consume, and losing biomass as a result.* 

Compensating For Infrared

Lowering the ambient air temperature with a sophisticated HVAC system may seem like an obvious way to deal with infrared radiation, but it comes with its own drawbacks. Introducing colder ambient temperatures to the grow room to bring infrared affected areas into the desired temperature range could knock areas not in direct light out of that range and into a cold zone.

Infrared radiation only affects the surfaces it touches, so any portion of the crops canopy that isn’t in direct light will have a lower temperature. The areas that are often neglected by HID lighting are at the bottom of the canopy, and closer to the center. As hot air rises, cool currents rush through the lower canopy, lowering the temperature and creating more cold zones.

Meanwhile, the upper canopy is getting cooked. Hot temperatures emanating off the lights mix with high leaf surface temperatures and rising heat. Even the beneficial photons emanating from the light add heat to the mix.

All photons absorbed by the leaf increase the leaf temperature; how much depends on the wavelength of the photon and whether or not it can be converted to chemical energy. Photons fully utilized by the plant in chemical reactions will heat the leaf less than photons which are absorbed but not utilized. Therefore, Less-efficient light spectrums will raise leaf surface temperature more, while, in more efficient spectrums, the leaf surface temperature will not heat up as much, as more of the light energy is being converted into energy.

As HIDs offer only slivers of the full PAR spectrum, they too fall victim to the pitfalls of their inefficiency. Combined with rising heat, hot lights and infrared radiation, the heat on the top of the canopy creates a huge temperature discrepancy with the bottom. Each section of the plant is working at a different rate, which stresses the plant and creates uneven budding throughout its branches.

Life With Less Infrared

When temperatures within the plant are uniform, it performs photosynthesis efficiently throughout the plant. The result is fuller, healthier plants from top to bottom, and, yes, higher yields.

Infact, by switching from HID to High Intensity LED lighting, growers can allow their ambient temperature to rise, saving electricity and lowering operating costs. While high temperatures can push plants into photorespiration, this can be avoided by increasing light intensity and by upping ambient CO2. By increasing CO2, you adjust the ratio of oxygen to carbon in the air, and give the plants more carbon to build with as they widen their stomata under the higher intensity light. 

The increase in carbon and photons pushes the plant to perform photosynthesis at faster rates and put on more biomass in less time. Full spectrum light provides an efficient source of energy for the plants, while a lack of infrared keeps leaf surface temperatures from broiling. The result is a larger yield of cannabis, with a fuller terpene profile, more cannabinoids and more of those beautiful crystalline trichomes growers love.

Interested in leaving infrared behind? Click below to get a free, custom-led light plan tailored to you. Switch to LED, and see growing in a better light.