Plants are dependent upon sunlight to fuel their organic activities; insufficient sunlight stunts or prevents plant growth, while overexposure to sunlight is harmful. Plants react to changing daylight patterns to prepare themselves for seasonal changes. Many plants flower in response to specific durations of sunlight and darkness.
Plants subsist upon sunlight that they convert into chemical energy through the process of photosynthesis. The three sunlight factors that affect plant growth are the quality, intensity and duration of light.
Light quality is the color or wavelength that reaches the surface of the plant. Red and blue light highly stimulate plant growth, while green light has minimal effect. Blue light promotes vegetative leaf growth. Red and blue light together stimulate flowering.
Light intensity refers to the amount of sunlight a plant receives. Plants normally grow in direct proportion to light intensity. However, too much light can scorch them. Most plants thrive in a condition of morning sun with afternoon shade. Reflected heat from buildings or other surfaces is a deterrent to plant growth.
Light duration is the amount of time that a plant is exposed to sunlight. Most plants are unable to handle continuous sunlight 24 hours a day. Twelve to 14 hours of light per day is a healthy light duration for most species.