MJBizMagazine September 2021 Lighting Buyers Guide - 16

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UNDERSTANDING HORTICULTURAL LIGHTING
A glossary of common terms
Horticultural lighting is riddled with technical jargon that can make understanding the fundamentals of
cannabis lighting complicated and lighting purchases confusing.
Plants respond to a broader spectrum of light than humans do, said Erik Runkle, a horticulture professor
at Michigan State University. Because of that, different measurement techniques-and terminology-have
been developed for horticultural lighting standards than what we use when measuring human light. Instead
of discussing lumens, lux and foot-candles, horticultural lighting manufacturers discuss photons, PAR and
micromoles (see definitions below).
Growers don't need to understand every nuance of a horticultural lighting system, Runkle said, but they
should have a solid grasp of the basic tenets of horticultural lighting and the most commonly used phrases.
Resources for more information about horticultural lighting include the Greenhouse Lighting and Systems
Engineering (GLASE) consortium established by Cornell University and the Rensselaer Polytechnic Institute,
and horticultural departments in local land-grant universities. For a comprehensive overview, see the
book Light Management in Controlled Environments, authored by Runkle and Roberto Lopez, a floriculture
extension specialist at Michigan State University.
CANNABIS LIGHTING GLOSSARY OF TERMS
Blurple Lights-Light emitting Diode (LED) lights that are a combination of red and blue emitting a purplepink
light. Blurple lights are very energy efficient and support early vegetative and flowering stages but don't
offer a full light spectrum.
Broad-Band Spectrum-LED lights that emit a wide range of wavelengths that promote plant growth,
including some that include far-red light. Broad-band spectrum LEDs are not as efficient at energy
conversion as narrow-band spectrum LEDs.
CRI (Color Rendering Index)-A measurement of how well a light source reveals colors to the human eye
compared to sunlight. Does a green look green? A red look red? A fixture with a low CRI may mask disease
or pest issues and could pose problems for indoor growers with no natural light source.
DLC Listed, Rated or Approved-DLC stands for DesignLights Consortium, a non-profit organization
formed to create and enforce energy-efficiency standards for horticultural lighting. A DLC-approved fixture
meets minimum energy efficiency standards, exhibits lifetime durability and has been constructed to
tolerate plant-growing environments.
DLI (Daily Light Integral)-The cumulative value of photosynthetic light delivered per square meter per
day (rather than per second). DLI and PPFD (Photosynthetic Photon Flux Density) are both ways to measure
how much light plants receive. DLI is the daily cumulative of PPFD.
Far-red Light-A wavelength that falls out of the definition of PAR but influences the plant's shape, how
large the leaves might become and how much extension the plant might develop, greatly affecting how large
a plant might become.
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MJBizMagazine September 2021 Lighting Buyers Guide

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