Leaves - Why do Some Trees Stay Green?

There are two types of trees, deciduous trees (which lose their leaves all at once) and evergreen trees (which lose a few leaves at a time and stay green all year).  Conifers are cone bearing trees that keep their leaves all year round (except for the larch!).  These trees first came from colder climates, so they are adapted to lower temperatures. The shape of their needles means that they can conserve more water and the needles also have a waxy coating to help with this. The needles also photosynthesise more slowly, but keep doing so all year round. Trees found in Tropical rainforests are also evergreen as the warm and moist climate all year round means there is no need for them to lose all of their leaves at once.