Match light to the species
Outdoor temperate trees generally need outdoor light and seasonal cycles. Tropical and subtropical bonsai may be grown indoors in cold climates but still need very bright conditions. A bright room to a person can be dim for a plant.
Assess the actual site
Window direction, obstructions, glass, distance from the window and seasonal sun angle change intensity. Rotate only when appropriate for the species and design; abrupt changes can stress plants. Observe internode length, leaf size, color and growth density as clues, but they are not substitutes for a light meter when precision matters.
Use supplemental light carefully
A grow light can help when natural light is insufficient. Follow the manufacturer’s distance and duration guidance and consider heat, photoperiod and electrical safety. More light is not automatically better if the plant overheats or cannot acclimate.
Avoid sudden exposure
Move plants gradually from shade to stronger sun, especially after indoor wintering. Protect leaves from scorch and monitor moisture as light and heat increase.
This page is reconstructed from historical BlogBonsai material. Horticultural details should be interpreted for the species, season, climate and condition of the individual tree.