Does a tree grow from the bottom or the top

I was looking at an aspen tree this morning on my walk and was wondering whether it grows from the bottom up (like hair growing from the root) or if it grows off the top.
My first guess is that it grows from the bottom (root) but if you look at a branch, it seems like it sends out shoots first instead of growing from the base.

Tree growth doesn't push the existing tree upward (like hair growth). Instead the existing tree grows new shoots for length and increases the size of shoots, branches, and trunks.

There are a few time-lapse videos on youtube that you might watch. Notice that one a branch is formed, the branch doesn't move.

http://www.youtube.com/watch?v=fA-l1t_Ao…

The growing areas of plants are called meristems,

The apical meristems are at the tips of the stems and they grow upward producing new nodes and internodes and leaves, this is how the length of the stem increases.

The width of tree stems increase by the growth of secondary or lateral meristems called the cambiums.