Key Metrics to look out for

Photosynthetically Active Radiation (PAR) – available light required for the photosynthetic process to take place. Refers to how efficient a lighting system is at converting electrical energy into photons of PAR. This is an essential component for the survival of a plant and will increase the speed at which a plant will grow. The photosynthetic range is found between 400nm – 700nm, which is also known as the visible light spectrum.

Photosynthetic Photon Flux (PPF) – the PAR (how much light/energy) that is emitted from a light source. This value is expressed as micromoles per second, µmol/s. In traditional lighting terms it is the equivalent to lumens – total amount of light a light source will give off

Photosynthetic Photon Flux Density (PPFD) – acutally amount of PAR (light/energy) that reaches the surface of the plant. This value is express as micromole per square meter per second, µmol/m2/s. In traditional lighting terms it is the equivalent to lux level on the surface at a particular distance – total amount of light that reaches the given task area at a particular distance from the light source

Uniformity – distribution of the light/energy that reaches the plant surface. Vital to look at the minimum, maximum and average amounts of PAR that reaches the plants surface

Efficiency – efficiency of the light source, micromoles per second µmol/s vs wattage. At a certain wattage a light source will give off a certain amount of light/energy.

Size – physical size of the space that requires illuminations and the size of the actually luminaire is important factor to take into consideration. Space is generally limited in indoor growing

Proximity – how close the light source can get to the plant, ideally it should not get closer than 12cm. Generally, the plant needs much light/energy as possible, so the closer the better while maintaining uniformity.


Primary metabolism which a chemical reaction that takes place within a plants leaves, assist in producing the nutrients for a plant to survive. Carbon dioxide, water and light are key requirements for this process to take occur. During this process by which plants originate and mature, develop leaves, stems, flowers and fruits. Three growth phases that occur:

Establishment growth
Occurs after seed germination or while rooting and establishing vegetative cuttings. Requires low light intensity

Vegetative growth
Occurs when leaves and stems are rapidly growing. Requires an increase in light intensity

Reproductive growth
Occurs when the plants transition to start producing flowers and/or fruit. Requires high light intensity

Secondary metabolism which is the process in which a plant develops form and structure, and this process is caused by light. It will assist the plants in developing colour, taste and smell 

Plants response to the changes in the day’s length, so affectively the plants circadian rhythms. This is vital in plants the flower and fruit. Short day plants require long periods of darkness for flowering to occur, while long day plants require short periods for flowering to occur

Forget WATTAGE – important to ask how much light/energy the light source gives off, Efficiency is vital. The higher the micromoles per joule μmol/J (how much PAR per watt you getting). Generally, the higher the light intensity requirement, the higher the wattage
Forget LUMENS – lumens do not correlate to photosynthetic grow rates, PAR (how much light/energy) that is being emitted by the light source
No “MAGIC SPECTRUM” – all wavelengths between 400nm to 700nm will grow plants. The GREEN spectrum does play a role in plant growth. A 50w LED light source cannot replace a 1000W HPS, same principals apply in LED in general lighting
Uniformity – Don’t look at a single PPFD measurement, unless you growing one plant. Vital to know how much PAR is being distributed across the entire canopy
Ability to deliver Light – don’t focus on wattage, efficiency in LED is generally a 50% reduction in comparison from traditional lighting. Light source ability to deliver light to the plant 
The amount of light delivered to your grow area (PPFD), the electrical watt consumption, and the light distribution pattern are important metrics to focus on
Maximize your yield per cubic space – Space is vital, utilizing the entire space of greenhouse/indoor area available will assist in this process. Able to achieve plant growth all your round 
Minimize operating costs – Operating in a more cost efficient manner, reducing the energy costs with LED lighting can reduce the lighting energy by up to 50%, LED’s run cool which in turn will reduce HVAC for additional energy saving. Reduction in water, space and labour are other contributing factors
Quality of crop – Improving the quality of the crop grown, achieving better colours, smells and tastes with less wastes


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