As a grower, you have a lot of things to care about. Plant lifecycles, grow light positioning, heat, light spectrum, space and market are all incredibly important factors to consider when building a greenhouse or grow area.

As you explore this world and unpack the different metrics and grow lights and systems that you need for optimum yields and healthy, flavoursome plants, you will hit a wall of acronyms. These acronyms – PAR, PPF, PPFD – sit alongside terms like watts, lumens, photon efficiency and LUX, and they are all critical to helping you create the perfect grow space and yield.

This isn’t as complicated as it sounds. In this guide, we explain exactly what PAR, PPF and PPFD mean, and exactly why you should care…

What is PAR (Photosynthetic Active Radiation)?

PAR stands for photosynthetic active radiation and describes the wavelengths of light that sit within the visible range of 400-700nm. It was originally defined by research undertaken by Dr Keith McCree in the early 1970s, and it is described as the type of light required for photosynthesis. PAR doesn’t measure light, it is rather a term that can help the grower determine the type and volume of light that’s needed to optimise plant yields and health. PAR light is leveraged by grow light systems to mimic natural light and can be optimised with other light solutions to change light density, usage, and measurements.

For the grower, PAR is a term that should be used to help fully realise optimal lighting layout and usage. It is also an important consideration when purchasing grow lights – ensure that you fully understand how much PAR they produce, how much energy they use to produce their PAR, and how much PAR is available for the plants. These are some of the basic considerations that need to be managed before you sign on that dotted line.

What are PAR, PPF and PPFD, and why should you care?

What is PPF (Photosynthetic Photon Flux)?

PPF is the term used to define the measurement of PAR. It stands for photosynthetic photon flux and its value determines how much PAR is being produced by any one lighting system over the period of a second. PPF is the second essential ingredient in your recipe to the perfect lighting for your grow space. This is what helps you to establish exactly how much of the light your grow lighting system is producing can be used by your plants for photosynthesis.

For the grower, measuring PPF requires equal parts understanding of the process and mathematical patience. There are PPF measurement tools available on the market, but you can work with a trusted partner who can help you create a lighting system that’s efficient enough to deliver the PAR and PPF you need. PPF is measured in micromoles per second (µMol/S) – one micromole is around 602 quadrillion photons (source: LED Gardener)

What is PPFD (Photosynthetic Photon Flux Density)?

The third part of the PAR equation is PPFD. This stands for photosynthetic photon flux density and it does more than just measure the PPF, it also measures the surface area. PPFD is measured in micromoles per square metre per second (µMol/m2/S) which establishes exactly how many PAR photons are landing on a specific area. PPFD is all about how many of those essential, photosynthetic photons are actually impacting the grow area and how well those lights are working when it comes to their output.

For the grower, it’s important to make sure that the PPFD data you get from your grow light manufacturer is accurate and covers the entire area of the light. It’s relatively easy to massage this information, so consider factors such as distance from the light source, a number of measurements that account for the average, and the minimum/maximum ratio before you buy. This is another great reason why you should work with a trusted grow light partner who can offer you relevant metrics and the right tools to fully benefit from PAR, PPF, and PPFD.