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  • Writer's pictureHemp Geo News

Lighting Code 101

Updated: Mar 11, 2020

by Rick Rainbolt

One of the Most Important Capital Investments.

It’s important to know the basics of Lighting. As I have traveled visiting grow operations the past two years, lighting continues to be a bottleneck in many grow operations.

As this industry matures, the need to maximizing your yield per square foot in greenhouses or indoor grow facilities will become a bigger point of focus.

Having the proper lighting will be one of the solutions that will make a big difference in maximizing yield.

Over the past several years, HGI has established several facility development vendor relationships, giving clients substantial cost savings, experienced advice and one-on-one customer service.

Before ordering any light fixtures, give HGI a call for competitive price quotes.



• HID - Varies with reflector size and bulb intensity

• LED – Lenses affecting beam angle

Power, in general, is defined as energy over time. Watts are defined as 1 Watt = 1 Joule per second (1W = 1 J/s) which means that 1 kW = 1000 J/s. A Watt is the amount of energy (in Joules) that an electrical device (such as a light) is burning per second that it's running.

Cannabinol plants require high photosynthetic photon flux density (PPFD) for photosynthesis and growth. Dual lamp CMH fixtures or 1000w HPS (Double or Single-ended) or MH fixtures (Single Lamp) are commonly used for maximum efficiency.

Fluorescent lamps for juvenile cuttings, and ceramic metal halide, metal halide (MH) and/or high-pressure sodium (HPS) bulbs for established plants.

Light placement is determined on PAR readings and how much heat the lamp emits.

Light placement can range from 3-4 feet to 6-8 feet above the canopy to take advantage of maximum light saturation and photon density. This will also help the plants avoid overexposure, minimizing the risk of heat and light burn, thus maximizing plant production.

LED bulbs are also an option and can be placed closer to the canopy (18-48 inches) with less risk of burning the plant with heat, but positions should be monitored and adjusted throughout growing to avoid light burn through overexposure.

One other note for LED systems is to make sure the LED unit covers the entire spectrum, Blue and Green light should be available during vegetation, and Red light should be made more abundantly available during flowering for greater encouragement.

In some LED units you are able to adjust the spectrums to the specific stage of growth that you are at. For example, "It is important that your selected LED units are capable of covering the entire spectrum or better yet are able to adjust the color spectrum to the current stage of growth that your plants are in."

Photo periods of 18:6 are optimal during propagation and vegetative growth, while a period of 12:12 is optimal to initiate blooming.

It is important that once the flowering cycle has been initiated the plants are not

exposed to light during a sleep cycle, since this may cause the plants

to become hermaphroditic and lower the overall quality.

Lighting Technologies

- Fluorescent

- CMH or LEC

- Metal Halide

- DE Metal Halide (DE: Double Ended)

- High Pressure Sodium

- DE High Pressure Sodium

- Induction Lighting

- LEP (light-emitting Plasma)


Light Measurements:

+ Light Measurements: Lumens, Lux, PAR and Micromoles

+ Highest lumens per watt? (Not the way to measure) Lumens and Lux:

• Lumens and Lux (Doesn’t tell you much about grow lights)

• Spectrum, Par, Photons and Micromoles (Are Helpful!)


Plants need light to produce their own food through the process of photosynthesis.

Also known as PAR (Photosynthetically Active Radiation)

PAR (400 – 700nm)


SPECTRUM (Like a Rainbow)

+ Wavelengths of light are measured in nanometres (nm)

+ Humans are sensitive to wavelengths of 500nm - 600nm

+ Plants are sensitive to wavelengths of 400nm – 700nm (the PAR area)

+ Wavelengths of light are often described as the PAR area


Blue light (around 400nm-460nm) Encourages vegetative growth, strong root growth and intense photosynthesis.

Red light (around 580nm-700nm) photosynthesis, stem growth, flowering, fruit production, and chlorophyll production.

+ Most growers use a dual spectrum light, which emits both blue and red light.

+ Many growers switch the lamp they're using for each stage of growth.


Used to measure how much

of this usable light is reaching

your canopy.

Lumens & Lux


+ Lumens measures light intensity. Lumens only relate to human eye sensitivity.

+ Remember: Lumens are for Humans; PAR is for Plants.


+ Lux tells you how many lumens fall on each square meter of a surface.

+ Lux is about lamp intensity, but not how useful a grow light is to your plants.

Photons and Micromoles

Don’t focus on lumens and lux – It’s about the photon and micromole count

in the PAR area. There are two types of photons:

A blue photon: Short-wavelength

A red photon: Long-wavelength


The Secret to Light Speed Growth

Plants cannot grow without light, and the amount of light reaching your plants greatly affects how well they grow.

Photons are the tiny particle waves of

energy that are more commonly

referred to as the term “light.”

Mimicking the Cycle of the Sun

• Spring & Summer: More blue (400-500nm)

• Early stages of growth, increasing blue light intensity

• Fall: More red (620-780nm)

• Red wavelengths in flower increases resin & flower density

PPFD Charts

Light overlay pattern – Hot spots and low light levels

- How many photons are hitting a given surface area. (PPFD)

- Total photon emittance from a fixture. (PPF)

Stages of Growth

+ Minimum: Clones & Seedlings: 100 umole

+ Optimal: Clones & Seedlings: 150-250 umole

+ Early Veg: 350 umoles

+ Veg: 400-600 umoles

+ Flower: 700 umoles (Low side)

+ 1000 -1200 max without Co2

+ 1500 max umoles with CO2 supplementation

When you see µMole, pronounced ‘Micromole’, is used as a unite of measuring the net energy in plant lighting and represents the large number of photons that fall within the PAR regions of 400-700nm spectrums over a fixed area.

To learn more about HGI’s Master Grow CERT programs or quotes on lighting, call or text Rick @ 704-965-89035

Rick Rainbolt


Hemp Geo Institute

Call/Text: 704-965-8935



PS: Quote of the Day...

“We must all wage an intense, lifelong battle against the constant downward pull. If we relax, the bugs and weeds of negativity will move into the garden and take away everything of value.”

                                           – Jim Rohn



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