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P.L. Light Projects

Washington University St Louis

The Plant Growth Facility at Washington University St Louis is used to support the University’s teaching and research needs regarding plant science and production. They have 5 research based greenhouses that have been in operation since 1985.

Project Details

Location: St Louis, Missouri

Crops: Corn, Rice, Clover, Grasses

Luminaires: HortiLED Top & Legacy Metal Halide Luminaires


Project Results

“Best looking corn I’ve ever had this time of the year” is how Washington University St Louis greenhouse manager, Michael Dyer, described their first crop of corn grown under P.L Light Systems HortiLED Top luminaires on a cloudy day in December.

Michael Dyer manages the Plant Growth Facility at Washington University St Louis where they have 5 greenhouses used to support the University’s teaching and research needs regarding plant science and production. Many of their research projects, including the corn being grown, are exploring important areas in plant genetics, ecology and molecular biology. So, having reliable luminaires for their many experiments is important for collecting consistent information and results year-round.

Corn being grown for research in one of the University’s greenhouses


The greenhouses at the University were built in 1985, and in the 1990s, they began installing P.L. Light Systems’ legacy MH luminaires. The MH luminaires have been a reliable supplemental lighting technology for them for well over a couple decades, however, they were limited by the amount of light intensity they could achieve. And since they do research on many high light crops such as corn, clover and rice, they needed more intensity to ensure proper growth and development.

Since then, one of the greenhouses has been retrofitted with the HortiLED Top luminaires  – this is where the corn research is being conducted.   With the MH lamps, they were only able to achieve a PPFD (Photosynthetic Photon Flux Density) of about 150 µmol – however, under the HortiLED Tops, they were able to achieve upwards of 350 µmol. This was ideal for them because they are located in the Midwest where they have limited sunlight hours in the winter.  In addition, they installed a pulley system so they can raise and lower the LED luminaires – this helps to increase or decrease the amount of light intensity being delivered to the crop canopy (since they have a non-dimming version of the HortiLED Top installed).


They noticed increased growth, density and pigment in the corn being grown under LED luminaires

What Michael was most impressed by was the deep penetration of light into the crop canopy from the LEDs –  he was surprised to see light reached even the lower leaves on the plants.  This is important to note because corn is a tall plant, often reaching 6-8 feet in height, and are planted quite densely.  When they installed the HortiLED Tops, they also kept the MH luminaires, creating a hybrid lighting system.  Keeping the MH lamps helps to provide heat in the cold winter months, and having the LEDs allows them to have supplemental light in the spring, summer and fall months without adding extra heat. This is critical, since many of their plants require 14-18 hours of daylight for proper growth and development.

Overall, making the switch to LEDs meant they saw greater density, speed of development and enhanced plant colour in the corn compared to the corn being grown under the MH luminaries alone.  Since they were thrilled with the outcome, they plan to retrofit all the greenhouses with LED luminaires to make them more efficient and better suited to growing all the high light crops they are conducting research trials on.

Learn more about the Plant Growth Facility at WUSTL by checking out their website at:

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