Short days put sunlight at a premium. Even houseplants feel it.
Mostly, they just sit and wait for better growing conditions. But for indoor gardeners who want plants to keep growing and even flowering this time of year, artificial light is the answer.
Visible light is only a small slice of the electromagnetic wave spectrum, which runs from the very short gamma and X-rays (with wavelengths measured in millionths of a meter) to the long radio waves (with wavelengths measured in kilometers).
