LED grow light intensity
To ensure optimal plant growth, adjust the LED grow light intensity based on the specific growth stage. Use lower intensity levels for seedlings and pre-vegetative stages (25-50%), moderate levels during vegetative growth (50-75%), and full intensity (100%) for the flowering stage. Seedlings thrive with reduced light intensity to avoid stress, while flowering plants benefit most from maximum intensity for robust development.
More growers are transitioning from traditional HID and fluorescent T5 grow lights to advanced LED lighting systems. Unlike HID lights, LEDs produce significantly less heat, allowing for different positioning relative to the plant canopy. Understanding the optimal distance for LED grow lights is crucial, as it directly influences the various stages of plant growth and development.
Seedlings and Pre-Veg
In their early stages, young plants are highly sensitive to light intensity. To support healthy root development and sturdy stem growth, it’s essential to begin with a lower light intensity—around 25-50%—to prevent undue stress.
Vegetative Stage
As plants mature and develop their leaves, their demand for light increases to sustain photosynthesis and growth. Gradually raise the light intensity to 50-75% to ensure they receive the optimal illumination for this stage.
How to Measure Light for Plants
Before diving in, let’s break down two essential terms: PAR and PPFD. PAR (Photosynthetically Active Radiation) refers to the part of the light spectrum (400nm-700nm) that plants can "see" and utilize for photosynthesis. PPFD (Photosynthetic Photon Flux Density), on the other hand, measures the intensity of the light (PAR) that a plant receives over a specific period, expressed in micromoles of photons per square meter per second (µmol/m2/s).
Think of PPFD as the sun "pouring" light onto plant leaves. As sunlight streams down, the leaves collect that energy to fuel photosynthesis. PPFD quantifies how much of this light is being delivered to the plants over time. This metric is crucial because it allows growers to precisely measure light intensity at the canopy level, ensuring plants receive optimal light for growth. Additionally, understanding PPFD helps prevent common issues like burning, bleaching, stunted growth, or discoloration, which can occur when lights are placed too close to the canopy.
Additional Considerations
Factors such as plant size, growing medium, and environmental conditions like temperature and humidity play a crucial role in determining the ideal light intensity.
Adverse Effects of Too Much Light
Cannabis plants can become stressed when exposed to excessive light at any stage of growth. While LED grow lights produce minimal heat, the primary concern is "light burn," a condition caused by overexposure. If grow lights are positioned too close to the plant canopy, side effects such as discoloration or stunted and irregular growth may occur. It's essential to recognize these signs early and adjust the height of the lights to prevent further damage.
Common indicators of light burn in cannabis include upward-curling leaves and a phenomenon known as "bleaching," where leaves near the light develop white or yellow discoloration. Another symptom is when the leaf veins remain green, while the rest of the leaf turns yellow. Monitoring your plants closely and making adjustments as needed can help maintain healthy growth.