I've started constructing the first type of tree model using the same techniques I used last year. My method for creating a low poly tree starts with a cylinder, of which you delete the top and bottom sets of faces to leave you with a hollow tube. I then extract faces in sets of 3 to create roots, playing about with the vertices to make them more crooked.
To create the branches it's a very similar process, I just extract out the cylinder in different angles and when it is at a length I am happy with I merge the set of vertices at the end to create a tapered point. I play around with the scaling of each 'ring' of vertices to ensure the branch becomes wider and appears more like it is growing from the trunk.
I repeat this process to create primary and secondary branches until the tree is 'full' enough. However, it will be the addition of the tertiary branches with leaves that give the tree its proper fullness.
