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How much light do I need?

The previous post offered an introduction to PAR and PPFD. The question is how much is enough light and when is it too much. Supplying your plant canopy with an even and adequate amount of usable light is vital, but supplying your plants with more than they need can be a waste of energy and money. This can also lead to negative impacts on your plants.

All plants are different but can be placed into categories based on light needs per day. This is known as Daily Light Integral (DLI). DLI is the amount of PAR received each day as a function of light intensity and duration. This is known as moles per square meter per day (µmol/m2/d). A direct correlation between how much PAR your plants are exposed to and for how long each day. Generally, the vegetative stage of plant growth requires 16 – 24 hours of light per day, while the flowering stage requires up to 12 hours of light per day. Below is a general breakdown of how much PPFD is needed for plants to thrive during the different stages of growth.

Sustainable VegProduction VegFlowering Plant
50 – 200 µmol/m2/s150 – 400 µmol/m2/s 400 – 1 000 µmol/m2/s

These numbers vary based on type of plant and environmental variables like the introduction of carbon dioxide into the environment. 500 – 1000
µmol/m2/s has been noted as an optimum for growth. Less than 500
µmol/m2/s and growth will be slow. Plants require additional CO₂ to utilise more than 1 000 µmol/m2/s.

How much light per plant

Chandra et. al. concludes that peak growth of Cannabis Sativa takes place at 1 500 µmol/m2/s at 30ºC when supplementing with CO₂. Growth steadily decreases with more light or at higher temperatures, resulting in wasted energy.

Continue reading How much light do I need?
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LUX, Lumens, PAR and PPFD

Continuing from our previous post on why red and blue features so prominently with LED grow lights, this post looks at measuring the effectiveness of grow lights.

Brightness of light is most often measured in lumens or LUX, but these measurements aren’t directly related to better growing plants. Both are aimed at how humans perceive brightness, mostly in green regions and mostly irrelevant to plants. Plants love blue and red wavelengths, and if you have an LED lamp that is registering in those colours only, it will not be very bright in lumens. This is misleading as the light will still be quite effective in plant growth.


Lumens don’t affect plant growth, but PAR or Photosynthetically Active Radiation does. PAR represents the range of light wavelengths most plants react to (400 nm to 700 nm). However, the actual unit of measurement used to quantify the amount of light is called PPFD or Photosynthetic Photon Flux Density. Light can be considered two very separate things – a wave or a particle – this is the confounding part of Quantum Physics.

When measuring brightness (lumens) or colour, the wave aspect of light is considered, while with PPFD measurements, the particle aspect of light is considered. Light particles are referred to as photons. PPFD measures how many photons are falling on the leaf in a certain period of time.


Imagine running across a street in the rain and wondering how wet your hair will get. It’s not important what temperature the droplets are, or what colour they are – you are just concerned with how many droplets will hit your head in the time you get to the other side. When you shine a light on a leaf, you can think of the photons as droplets that you have to measure. It’s not the brightness of the light that’s important, it’s the number of photons that are striking the leaf and starting the photosynthetic reaction.

Measuring photons

PPFD is the unit of measure for how many photons hit a defined area in one second – defined by μmol/m2/s or micro-moles of photons falling on a square meter per second. μmol is 1,000,000th of a mole. A mole is just a number that aids in counting very small objects, like photons.


Understanding PPFD means understanding the particle nature of light – photons. PPFD measures how many photons are falling on a leaf, determining the amount of vital photosynthesis that can take place.

We’ll be looking at how much light is needed for an indoor grow in the next post.

Continue reading LUX, Lumens, PAR and PPFD
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Why so many LED grow lights are red and blue

Blue and red spectrum LEDs are the foundation of most LED grow lights and the resultant hue is sometimes referred to as blurple. There are good reasons why red and blue spectrum LEDs are the foundation of most LED grow lights and this post is the first in a series aiming to better understand the science behind LED grow lights.


Understanding why red and blue LEDs feature so prominently in LED grow lights starts with understanding chlorophyll in plants. Chlorophyll is vital for photosynthesis and allows plants to absorb energy from light. Plants are perceived as green because chlorophyll mainly absorbs the blue and red wavelength and reflects the green. The figure below plots the absorbance by the wavelength of light and illustrates the high absorbance of red and blue light in plants.

Spectrum Absorbance - LED Grow Lights

Most green land plants have two main types of Chlorophyll – Chlorophyll A and Chlorophyll B. Chlorophyll A is the primary active pigment (chemical) in photosynthesis. Chlorophyll B is called an accessory pigment. There are many other classifications of Chlorophyll other than A and B, but an in depth discussion of their functions are not necessary at this point.

The spectral range (wave band) from blue to red light is called photosynthetically active radiation (PAR). The spectral range of solar radiation from 400 to 700 nanometers is therefore the range of light that photosynthetic organisms are able to use most efficiently in the process of photosynthesis.

PAR is discussed in more detail in the next post.

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tCheck CBD vs THC Testing

A frequently asked question is how to test CBD and THC on the tCheck when there is no setting to choose beforehand. Below is the current status as of 2019/02/01.

Strains with a 1:1 CBD to THC ratio will not work until the latest update is sent. Most strains are either predominantly CBD or THC. For example, with 2-3% CBD and 18% THC, the device will give the THC reading because it is the dominant cannabinoid. CBN or CBG are naturally pretty low and aren’t being tested for. 

An update is planned that will display decarboxylation completion and display both THCa and THC results. 

Reach out to support and tCheck can look up the device and give specific information for previous tests.

results | tCheck cannabis infusion potency tester
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tCheck 2 and Flower and Concentrate Kit Features

tCheck 2 and flower and concentrate kit features chart. tCheck 2 and flower and concentrate kits come with a 6 month warranty.




tCheck 2 base

Compound breakdown subscription (TBA)

Flower & concentrate kit

    Requires tCheck 2 base Requires tCheck 2 base
Compound by volume measurement Yes Yes Yes
Coconut oil Yes Yes  
Butter Yes Yes  
Olive oil Yes Yes  
Alcohol Yes Yes  
iOS app Yes Yes Yes
Android app Yes Yes Yes
History log Yes Yes Yes
THx and CBx breakdown   TBA TBA
Plant material     Yes
Concentrates     Yes
Recommended price R4 800 $15/month (USD) R3 200