I would use After Effects. I would create the outline of the tree in black and white silhouette.
Then I would hand keyframe the 30 -40 characters to fly up and rotate or whatever you choose, to
various areas of the trees limbs and trunk. Use the black and white tree silhouette as a luminance mask,
Which will clip the letters perfectly to the shape of the tree. That is the "simple" way to go.
Personally I would also apply a mesh warp over the tree shape, that was distorted to the edges of the tree
and effecting the text animation layer (precomped) I would also animate each text piece to 'scale\grow' upward from the next piece of text in that 'sprouting' way.
Animation & Visual Effects
Los Angeles Ca