Light serves as the essential energy source for plants, fueling photosynthesis, the process that transforms light into chemical energy. The Unlikely Gardener’s PAR Map Visualizer lets you easily visualize how your grow light distributes Photosynthetically Active Radiation (PAR), measured in μmol/m²/s (micromoles per square meter per second), across your plant’s foliage. This is a close enough approximation that will allow you to place your lights in the most advantageous ways so your plant's get the light they need for their best potential growth.

A few facts about light levels

• Unobstructed light from the sun at noon in a clear sky delivers approximately 2,000-2,200 μmol/m2/s.
• A fully overcast sky will usually deliver somewhere between 300-500 μmol/m2/s, sometimes higher.
• Partial shade, often referred to as dappled sunlight will average around 400 μmol/m2/s give or take 50 μmol/m2/s 
• Full shade, i.e. out of direct sunlight, often referred to as bright-indirect light will usually deliver 200-300 μmol/m2/s
• Deep shade, usually with an obscured view of the sky, will often deliver 100-200 μmol/m2/s
• Light between 20-50 μmol/m2/s is the bare minimum to keep most small plants alive, but they'll generally suffer.  

Different plants have varying light requirements, and understanding light intensity helps plant parents optimize growing conditions. By visualizing how light intensity changes with distance from the source and from natural fall-off, you can better plan your plant placement, choose appropriate/better grow lighting, or decide on the best locations/height your lights.

Key points about light intensity and plant growth:

• Insufficient light ( <50 μmol/m2/s ) can lead to weak, etiolated plants, that struggle.
• Optimal light levels promote healthy growth, robust stem development, and maximum photosynthetic efficiency
• Excessive light can cause leaf burn, increased water needs, and photoinhibition (a decrease in photosynthetic capacity)
• Light intensity decreases rapidly as distance from the source increases, following the inverse square law
• Indoor plants and greenhouse cultivation require careful consideration of light intensity to mimic natural conditions
• Understanding PAR helps in selecting appropriate grow lights and determining their optimal placement
• Different growth stages and plant species may require adjusting light intensity for best results

Use the PAR Mapping tool below to explore how light intensity changes with distance and to determine the optimal light conditions for your plants.