If you are growing cannabis indoors, you might be wondering how to choose the best lighting for your plants. One of the most important factors to consider is PPFD, which stands for photosynthetic photon flux density. PPFD measures the amount of light that reaches your plants in micromoles of photons per square meter per second (μmol/m 2 /s). PPFD determines how much energy your plants can use for photosynthesis, which is essential for their growth and development.
Different stages of cannabis growth require different levels of PPFD. Cannabis seedlings don’t need too much light, PPFD levels of around 200-300μmol/m 2 /s are sufficient in combination with (around) 18 hours of daily light. The small size and delicate seedling tissues are easily overloaded and damaged by excessive light levels. Cannabis is often given light with PPFD levels of around 300-500μmol/m 2 /s during vegetative growth. Some growers will offer even stronger PPFD levels of around 600 though others might argue such PPFD levels are not really required in veg. During vegetative growth the plant will produce leaves, branches and roots but no buds.
The most important phase for lighting is the flowering phase, when cannabis plants produce buds. This is when they need the highest PPFD levels to maximise their yield. A general rule is to aim for 40 moles of light per day, or 40,000,000 μmol, per day. This means that your grow light will need to emit at least 925 PPFD for 12 hours straight during the cannabis flowering phase. However, some strains can tolerate even higher PPFD levels up to 1500 or more without showing signs of stress or damage.
To choose the best lighting for cannabis, you need to consider not only the PPFD level but also other factors such as PAR (photosynthetically active radiation), PPF (photosynthetic photon flux), DLI (daily light integral), wattage and efficiency. You also need to make sure that your grow space has adequate ventilation and cooling systems to prevent overheating and humidity problems. The best way to measure your lighting performance is to use a PAR meter or a quantum sensor that can give you accurate readings of your PPFD level at different points in your grow area. By adjusting your lighting height, intensity and duration according to your plants’ needs, you can optimise their growth and yield.