1. How much light does hemp need? 

Hemp production has distinct growing stages, and each has important photoperiod and light-intensity requirements. Twelve hours of darkness initiate flowering on hemp plants (other than autoflowering varieties), and a minimum of 18 hours of light for vegetative growth stages produces strong plants. As plants move through the growing stages, the photoperiod decreases, and increased light intensity allows for maximum yields and high cannabinoid content.  In the flowering stage, we recommend targeting a minimum daily light integral (DLI) of 30 moles per square meter per day. This is optimal for proper development and a high-quality product and yields. In fall, winter and early spring, outdoor light levels fall below this level, so supplemental light becomes essential to maintain your desired DLI. 

2. How do I choose the best lighting system for my facility?

Do your research on lighting suppliers, and ensure they have a background in horticulture and can stand by their products. P.L. Light Systems has been designing and manufacturing horticultural lighting products for 40 years, so we understand growing.  

Other considerations include checking for the company’s Canadian Standards Association (CSA) or Underwriter Laboratories (UL) product safety certification. If you are opting for LEDs, check if they are DesignLights Consortium (DLC)- certified, which can help you receive rebates from your local energy providers. DLC certification also validates any product performance claims, including light output and energy efficiency. 

Growers should target a daily light integral of 30 moles per square meter per day.
Photos courtesy of P.L. Light Systems

3. What is the best lighting technology for my application?

Choosing between high-intensity discharge (HID) or LED luminaires can be a big decision and depends on many factors, such as your environment, goals, varieties and budget. Both have advantages and disadvantages. Setting up a trial R&D area for LED technology allows you to see how different varieties respond to the same wavelengths. And installing a hybrid lighting system with both HID and LED luminaires allows you to take advantage of the energy savings and spectral efficiency of the LEDs, as well as the radiant heat and uniformity of the HID luminaires. 

4. How many lights do I need to install in my facility?

Any reputable lighting company will design a light plan for your facility that calculates the number and best coordination of luminaires needed.

You need a uniform light distribution for even photosynthesis to ensure uniform growth and development. P.L. Light Systems advises growers to consider a light plan that shows a guaranteed uniformity and light level. 

5. How do I measure ROI? 

Yield is the most important measurement of profitability, and understanding yield metrics is important to make sure you get the most out of your lighting. Supplemental lighting can allow for an increase in plant density, as well as in quality and yield. One way to measure yield for hemp is in grams/kilograms/pounds per square foot. Measuring yield allows the grower to understand how well the space is being utilized, if grow conditions need to be adjusted, or if some varieties produce better than others. Other considerations should be price per unit, energy use efficiency, maintenance costs and infrastructure costs. 

For more information, visit pllight.com.