A healthy indoor bonsai requires plenty of light. The right wavelengths, intensity and duration are needed to drive photosynthesis. Unfortunately, many home growers misunderstand how to provide this light or use it inefficiently, resulting in stunted growth and less than ideal health.
The first step is to assess the amount of natural light your tree receives throughout the day. If your bonsai is located near a bright window and receives full sunlight from morning to afternoon, you might only need to supplement the lighting for a few hours each day to mimic the sun’s movement and fill in gaps caused by cloudy days or shorter daylight hours.
If your indoor bonsai trees are tropical species (such as Ficus benjamina or Serissa), consider using fluorescent grow lights. These produce a cool light spectrum that mimics the softer daylight your tropical bonsai might receive in a well-lit room. They also produce very little heat, reducing the risk of overheating your plants’ foliage.
LED grow lights are another popular option. They are energy-efficient and last a long time, and they don’t produce much heat. These bulbs also come in a wide range of color temperatures, which makes them suitable for both fruiting and flowering bonsai species as well.
HID grow lights are more powerful than other types of lighting. However, they can cause the plant to overheat if placed too close, and their high light output can damage lower branches that may be inadvertently overshadowed. Because of these issues, HID lights are not ideal for all indoor growing situations.