For dull rooms facing north or east, several Bonsai species will be perfectly happy if kept in a position close to the window to expose them to sufficient light.
Installing purpose-built artificial lighting for your indoor Bonsai collection is another solution to overcome this problem and is not as costly or impractical as it might seem at first thought.
Ordinary blue-white fluorescent lighting is cheap to run and will provide the complete spectrum of light needed by most Bonsai species, although there are many horticultural lighting systems available. The only drawback is that the light is of low intensity.
Lighting should be positioned directly above, at the back and front of the Bonsai trees, ideally 20-30 cm from the foliage. Keep the lights on for 7 to 10 hours a day. Rotate the trees through 90 degrees every few days to ensure enough light reaches all parts of your Bonsai trees.
The slight heat generated by the lights is also beneficial for the Bonsai. Keep in mind however that the heat will have a drying effect on the plants, which means it needs to be countered by regular spraying and watering.
Indoor Bonsai species suitable for dull rooms: