Targetes (flowers) under a growlight

Safe use of grow lights

Light spectrum


Fig. 1: Light is a form of electromagnetic radiation that travels in waves. It can be described by its wavelength, which is the distance between two consecutive peaks of the wave. The wavelength of light determines its color, and the range of wavelengths that are visible to the human eye is referred to as the visible light spectrum. This spectrum encompasses wavelengths ranging from 400 nanometers (nm) to 700 nm, with 400 nm marking the boundary of ultraviolet light and 700 nm marking the boundary of infrared light.

visible light spectrum and plant spectrum

Fig. 2: The sensitivity of the human eye and that of plants differ in terms of the spectral regions to which they are most responsive. While the human eye exhibits a relative peak in sensitivity in the green region of the spectrum, plants have relative peaks in both the red and blue regions. This difference in sensitivity allows the human eye to perceive the world in a distinct way, while enabling plants to efficiently use light for photosynthesis and growth.

Potential problems with grow lights:

While traditional LED grow lights have been designed specifically to optimally support plant growth and development, they may pose certain challenges in certain environments. These lights typically feature a primarily red and blue light spectrum, as these two colors are essential colors for plant growth. However, this limited spectrum can create potential problems when traditional LED grow lights are used in environments where people are sharing the same space. In such cases, it is recommended to only use these lights in enclosed growth chambers to reduce potential health and wellbeing concerns.

plant under purple grow light

Fig. 3: An example of the purple hue from a traditional Red and Blue Grow Light

The combination of red and blue lights can produce a strong purple hue, but the human eye is not as sensitive to these colors, leading to the perception of the light as dim even when it is actually quite bright. This can cause eye fatigue and make it difficult to see objects clearly. Additionally, the lack of green light can negatively impact the accuracy of color perception by the human eye.

To ensure that our HortiPower lights provide optimal conditions for plant growth, while also promoting health and well-being for people, they incorporate a moderate amount of white light that includes green. This results in a white light with a reddish tone that is not pure white, but remains highly effective and efficient for plant growth and development.

The color rendering of a growth light is expressed through the Color Rendering Index (CRI), which ranges from 0 to 100, with 100 representing natural daylight. The Nurser 3 has a CRI of around 65 to 70, which is on par with minimum requirements for street lighting.

Nurser 3 spectrum

 Fig. 4: The Nurser 3 spectrum

Other considerations:

In some instances, such as grow tents and greenhouses where high-wire crops are grown, growers may use fixtures with a wattage of 600W or higher to provide the necessary light for these crops. However, due to the high wattage, these fixtures need to be installed at a greater distance from the plants, resulting in more spill light and intense light on the human eye. In such cases, especially in grow tents, it is recommended to wear sunglasses as the human eye may not have sufficient time to adjust to the brightness in the grow tent, and the light dispersion angle may result in a significant amount of light shining directly into the eye.

The Nurser 3 lights are primarily designed to be installed closely to the crops, minimizing spill light and directing light directly onto the crops. While sunglasses can still be used with Nurser 3 lights, they are not mandatory.

Herbs under grow light

Fig. 5 Herbs under a Nurser 3 grow light

Some grow lights may contain ultraviolet (UV) light, which can be harmful to humans and influence molecular structures. It is not recommended to use UV light in grow lights, even with the use of sunglasses, as UV lights must undergo a different certification process and require specialized training to understand the risks and best practices associated with their use.

While some grow lights may be 100% white light, these are often standard LED lights that lack sufficient red and blue, leading to plants that grow tall and thin. The Nurser 3 lights, on the other hand, are designed to produce strong and vigorous plants.

It is important to avoid looking directly into the LED lights, as this applies to all lights. If the grow light feels too strong while you are harvesting or working in the same space, adding a few general white light fixtures in the space can help to mix the grow light with ambient light, making it more comfortable for the human eye.

Finally, if you are working at a computer or laptop in a growth-environment with grow lights, it is recommended to position the grow lights out of your line of sight, as the brightness of the screen and lights are different, leading to constant eye adjustments. This is a general principle that applies in any environment.

Back to blog