Page 24 - Tài liệu cây cảnh Bonsai4me Bonsai Basics

of dormancy which is only triggered by cooler temperatures. Without this
dormancy, trees can continue to grow for anything up to 2 years before going
dormant whatever the season or temperature; this enforced dormancy can often
be fatal.

The leaves of an English Elm bonsai turning yellow as the tree enters dormancy.
Ulmus minor bonsai, 17"/42cm in height,by Harry Harrington
Secondly, it is difficult to provide adequate growing conditions for trees
indoors. Inside, light levels are lower, humidity levels are very poor and trees
suffer from lack of air circulation. For species that are hardy to frosts, it is far
better to cultivate them outside all year round where conditions are conducive to
their health and vigour.
Tropical species of bonsai on the other hand require temperatures above
around 10-15°C (depending on individual species). In cool temperate areas of

America and Europe this can mean that many tropical bonsai can only be kept
outside for 2 or 3 months of the summer, the rest of the year adequate care must
be provided inside.
Light
Indoors, light levels are very poor. Though imperceptible to the human eye,
light levels drop rapidly the further you are from a natural source of light. It is