Plants receive nutrition from three sources. There are nutrients in both the water that they drink and the soil that their roots grow in. But plants also make their own nutrition through photosynthesis from the light they absorb. All plants need a certain amount of light to grow. High light-requiring plants such as cactus need much more light than low-light requiring plants such as the snake plant or peace lily. One method to assure that a plant receives sufficient light to thrive is to supplement natural sunlight from a window with grow lights.
Determine how much light a plant needs to thrive. Many purchased house plants have this information included in care instructions on plant tags or stickers. You can also determine if a plant is a high-light requiring plant, medium-light requiring plant or a low-light requiring plant by researching the plant's native environment. Plants that come from a desert such as aloe vera plants are high-light requiring. Plants that come from the floor of tropical rain forests such as devil's ivy are low-light requiring plants. Medium-light requiring plants may include African violets and moth orchids. These plants grow in shady mountain locations as well as the subcanopy of lowland and tropical rain forests. You can also ask professionals at garden centers, plant nurseries and master gardener programs what the lighting requirements of a particular plant may be.
Position your plant in your home so that it will receive some natural lighting. Plants with high lighting requirements should be placed in direct sunlight in a south-facing window. Plants with medium lighting requirements should be placed in a western window or out of direct sunlight in a south facing window. Plants with low lighting requirements should be placed just out of direct sunlight in a western facing window or in an eastern facing window. Natural light will provide wavelengths of light that a plant needs but cannot get from artificial light.
Select LED plant lights that produce light in the red and blue wavelengths. These wavelengths of light are the ones that a plant can most easily absorb and use. Plants are not able to absorb green wavelengths well enough to thrive beneath this light. Most plants appear green because they are reflecting green wavelengths of light rather than absorbing them.
Purchase the correct number of LED lights for the plant you are lighting. Low-light requiring plants require less than 250 foot candles of light, which is equivalent to a 20 watt fluorescent light bulb placed 24 inches above the plant. Most 2 watt LED lights output the equivalent of a 75 to 110 watt incandescent bulb. So you would use 1 LED light on a low-light requiring plant and hang it between 36 and 48 inches from the top of the plant. For medium-intensity lights require between 50 and 1,000 foot candles of light. A single LED placed 12 inches from the top of the plant will provide enough light for medium-light plants. High-light requiring plants need over 1,000 foot candles of light. For these plants, add a second LED to provide the light that they need.
Observe your plants as they grow and adjust your LED light distance accordingly. Plants that do not receive enough light will become weak and spindly and their foliage will noticeably lighten. Plants that receive too much light will have white patches that are the plant equivalent to sunburn.