A Fork in the Stem
There are two basic groups of trees, those that keep their leaves all year round and those that don't. The former being referred to as evergreens, because they're leaves are constantly green and on the tree, only succumbing to old age after a number of years. Most trees, however, will fall into the latter category, those which annually drop their leaves and re-grow them every spring. These two types of trees have very different leaves as well, most importantly is the size of the leaf, with broadleaved trees having much larger leaves to allow for the maximum amount of exposure to sunlight and thus the most sugar production from photosynthesis. The evergreens, on the other hand, have a much smaller, needle-like leaf that is coated in a waxy outer-layer in order to retain moisture and fight off the colder temperatures better.
These two leaf types have their give and takes as well. While the broadleaved type trees are able to grow large quickly and build up vast stores of sugars for extended growth throughout the winter, they must rely on their larger leaves in order to produce the vast quantities of nutrients they need in order to maintain this growth pace as well as their survival through the cold months. But, because of the significant surface area to volume ratio of these leaves, they are unable to stave off the cold of winter and instead must be dropped to conserve those food stores for the rest of the tree.
Evergreens, with their many tiny needles, retain their ability to produce nutrients and food throughout the entirety of the year, but because of how little area they have to photosynthesize, they must make up for it in numbers rather than size. With thousands of long, slender leaves, the evergreens are safe to grow all year long rather than stop to conserve their energy like the broadleaved trees. However, because of their inability to produce as much food, the evergreens will grow at a much slower rate.