Lighting Strategies for Leafy Greens

Jillian Whitehead

Cultivation Guide, Growing Advice, Leafy Greens | September 16, 2020

Greenhouse and indoor grown leafy greens and culinary herbs provide many advantages over field grown crops, including a more stable climate, more consistent time to harvest, the ability to control lighting, shading, CO2, and increased food safety. Low ambient light levels in the winter and on cloudy days, makes supplemental lighting essential for producing high quality, uniform greens year-round.  Since lighting is tied to overall quality and yields, it becomes important to have a reliable lighting system that can deliver on the goals you want to achieve.  With so many lighting options on the market, deciding which direction to go can be overwhelming.  At P.L. Light Systems, we produce and sell both HID and LED luminaires, and have been helping North American growers to build their businesses and achieve their goals for 40 years.

For more information download our Leafy Greens Crop Cultivation Guide.

– Explore the basic concepts of how the light environment affects plant growth

– Learn about lighting requirements for leafy greens, microgreens and culinary herb production

– Discover what lighting system works best for your application

Download The Guide

 

HID LIGHTING SYSTEMS

High Pressure Sodium (HPS) Luminaires have long been used by growers for a variety of leafy greens, including lettuces and herbs.  HPS luminaires, because they direct heat onto the crop, are well suited to growers in Northern Climates, who rely on the heat to improve crop quality and to help offset heating costs.  We have worked with growers such as Old Souls Farms in Saint Paris, Ohio, who use P.L. Light Systems’ NXT-LP luminaires with Alpha reflectors, to grow high quality greens year round.

Lettuce seedlings at Old Souls Farm greenhouse
Old Souls Farm who use the NXT-LP to grow high quality leafy greens and herbs

For growers looking to use HID luminaires we recommend either the NXT-LP, for low ceiling applications, or the NXT2.  Either of these high efficiency luminaires are designed to achieve optimum light intensity, and evenly distribute the light across the surface of the crop―with fewer luminaires.

For growers looking for a balanced, broad-spectrum HID luminaire, we recommend our high efficiency NXT-LP CMH 315W luminaire. Ceramic Metal Halide (CMH) luminaires emit a balanced and highly stable light spectrum, similar to natural sunlight, making them ideal in sole source growing applications. They also have a lower wattage (315W), than other HID luminaires―perfect for growing leafy greens in low ceiling or vertical growing environments, since they can be placed closer to the canopy, without burning the crop.

CMH luminaires in a vertical leafy greens aquaponics set up
CMH luminaires provide an ideal, balanced spectrum for leafy greens production. They are ideal for vertical systems as they do not burn the crop because of their lower wattage.

LED LUMINAIRES

LED luminaires can be a great choice for many leafy green growers thanks to their high efficiency and ability to dissipate heat away from the crop.  Other advantages of LEDs over traditional lighting, include PAR efficacy, ability to target specific wavelengths and control over light intensity (dimming).

Lettuce greenhouse with HortiLED Top luminaires overhead
Red-White (Medium) Blue HortiLED Top Luminaires have been designed specifically for greenhouse applications in mind.

What we recommend for greenhouse growers is the HortiLED Top 2.0, in the Red-White (Medium Blue) Spectrum, which is optimized for plant growth and photosynthesis.  See how DeGoede Farms, a leafy greens grower in Oregon, has used the HortiLED Top to expand their business and supply year round greens for their region.

For indoor operations, we recommend using the HortiLED Top 2.0 Daylight spectrum, which has been optimized for plant growth in sole source lighting applications.  For close canopy, or tightly-tiered vertical operations, the HortiLED Multi would make a great choice since it is designed for vertical racking systems.

Basil crop with HortiLED Multi luminaires in background
The HortiLED Multi is a great option for close tiered vertical racking systems

HYBRID SYSTEMS

There are many benefits and advantages to both LED and high intensity discharge (HID) technologies and one of the best ways to take advantage of them, can be to implement a hybrid lighting system. A hybrid lighting system is where a growing facility installs both LED and HPS lighting (or even two different styles of lamps such as combining HPS and MH) in one grow space. In the case of an LED/HPS hybrid application, this combination can provide the ideal balance between diffuse light distribution and spectral efficiencies. It allows the flexibility to take advantage of the radiant heat from the HPS lighting, but also to extend the supplemental lighting period longer into the spring by using the LED lights only when outside temperatures and daylight hours increase. For more information check out our blog on hybrid lighting systems.