Bonsai Light Requirements
The amount of light a bonsai tree receives is crucial for the tree to grow properly. Indoor and outdoor trees have different needs as they are different species. Time of year is also a factor in how much light your bonsai may need, particularly for outdoor trees. If you think your tree is getting too much, or not enough, light, there are things you can do to fix it.
Indoor bonsai trees are either tropical or subtropical. The reason only these trees can survive indoors is they need high, stable temperatures all year, as opposed to outdoor bonsai that need to be exposed to all the seasons. These trees need constant light all year round, for at least 5 hours a day, in order to survive. In order to receive this light, they need to be placed in front of a South facing window at all times. If the tree is moved away from the window by even a few feet, the light intensity will decrease significantly and can eventually kill the plant. An indoor bonsai needs as much light as it can get, and light from the sun isn’t always enough. Grow lights may be required for many trees.
Outdoor bonsai trees need lots of direct sunlight. However, too much sunlight can be a problem. Too much sunlight can burn the tree’s leaves or make the tree more prone to diseases and pests as their internodes and leaves grow too large. If your summers are especially hot, a spot in your garden or balcony where the tree can get afternoon shade is preferable.
Time Of Year
For indoor bonsai trees, the time of year does not affect how much light they need. They need a high, consistent amount of light all year round.
On the other hand, outdoor bonsai have dormancy periods in the winter, and have different requirements as a result. During this dormancy period, the trees stop growing and do not need as much light. It is completely normal and healthy for the trees to not receive as much light, or even as much water, in the winter. Do not try to bring the tree out of dormancy by heating it, this will kill the plant.
Even if your bonsai tree, indoor bonsai trees in particular, are receiving as much sunlight as possible, it is still likely that your tree is not getting enough light. Sometimes, even outdoor trees need artificial light if they are particularly picky. In this case, the grow light should be used to mimic the passing of the seasons, running the lamp longer in the summer, shorter in the winter.
Buying a smart grow lamp is another option. Smart grow lamps are able to track the time of day and period of the year. This is a very easy way to make sure your bonsai is getting enough light without lots of hassle.
While bonsai trees thrive with lots of light, sometimes, in certain climates, too much direct sunlight can be harmful. In areas with extreme heat and humidity, a shade net can be used to protect your tree form the harsh climate. Signs that your outdoor bonsai is being harmed by the sunlight include dried leaves and having to water constantly as a result of water evaporating too quickly.
Shading cloth is measured by the amount of light allowed to infultrate, ranging from 40% to 80%. 40% cloth is typically used for temperatures ranging from upper 80 to lower 90 degrees Fahrenheit. 60% cloth is recommended for temperatures in the mid 90’s to 100 degrees Fahrenheit. And for temperatures over 100 degrees, 80% cloth is recommended. Shading cloths can also be used to protect trees from excessive wind.
The amount of light a bonsai tree needs is determined by the placement, time of year, and species of the tree. Indoor trees need consistent light all year round because they have no dormancy period. Even right up against a South facing window, it is possible that your tree is not getting enough sunlight and needs artificial lighting. This artificial lighting should be used for around 10 hours a day for the best results. Outdoor trees, on the other hand, do have dormancy periods. During this time it is okay for outdoor bonsai to not receive as much light as they do in the summer.