The Wattage for Artificial Light to Affect Plant Growth

Wattage Requirements

• The amount of wattage required to keep indoor plants healthy is typically applied for each square foot of growing space that the plant occupies. Smaller plants will require less light, and the wattage is also affected by the light requirements of the plant itself. Some plants are referred to as low-light plants, meaning they can thrive in indirect sunlight and under artificial lights that give off as little as 10 watts for every foot of space the plant occupies. Medium light plants tend to require about 15 watts per foot of growing space, while the brightest artificial grow lights will be used for high light plants. These types of plants can be difficult to grow indoors even when sunlight is augmented by grow lights that provide high-intensity light with more than 20 watts.

Fluorescent vs. Incandescent

• Different kinds of bulbs give off different colors of light within the spectrum; for the best results, wattage should be divided between fluorescent and incandescent bulbs. Fluorescent bulbs tend to give off light that falls into the blue spectrum, while incandescent bulbs give off red light and higher heat levels. To reach a balance between the light colors and the heat, figure out how many watts are needed for your particular plant by multiplying the needed wattage to fulfill light intensity requirements for that variety. Then divide that wattage between fluorescent and incandescent bulbs, using one incandescent bulb and supplying the rest of the wattage requirements with fluorescent.

Positioning

• Mixing the two types of light bulbs will allow you to reach the appropriate wattage needed for the plant without worrying about the bulbs generating too much heat. Begin by placing the bulbs between 11 and 17 inches above the top of the plant. This will give the plant the maximum benefit from the correct wattage of light bulbs. If possible, place the plant near the center of the bulb when using tube bulbs, as this will produce the brightest light.

Outside Factors Impacting Wattage

• The wattage of a light bulb will fluctuate over time, and as the bulbs age, they will dim. When this begins to happen, the plant can begin to look as though it it not receiving enough light: Leaves might begin to fade, and the plant may start to move as though reaching toward the light. To prevent this from happening, take note of the life span of the bulbs as you are installing them, and replace them as suggested even if they still work. This will ensure that the plants are still getting the proper wattage. Bulbs may also need to be cleaned regularly, as dust and dirt can also change the actual amount of light that the plants are receiving.