After finally finishing the design for the door, I began work on the model in Maya. I decided that the first thing I should do was to start with the roots that surround the door. My first idea as to how to tackle this task was to extrude large cylinders to make the shape of the two "main" roots.

I then attempted to do the same for the other roots and then merge them together. This proved to be extremely difficult and involved far too much freehand vertex manipulation which ended up with an extremely messy mesh. I then, abandoning that method, attempted to extrude the sides of the main roots to create the smaller ones.

This, not only looked ugly, but also proved difficult when doing this with more than one attached root. Although I am sure there were ways to get this method working, I decided it would be easier to try a new method.
I started again by creating the rough shape of the base of the roots with the "create polygon tool" and extruding up. I then merged a few of the verts that made the gap between the roots, while keeping everything as quads. I ended up with a low poly version of what I wanted.

Although I could have subdivided this manually with the "Insert edge loop tool" I realised that this too would require far too much freehand vert manipulation, which is very fiddly and often very inaccurate. I realised I could get a much better result if I import the mesh into mudbox, subdivided once (would have like to have sub-ded more but didn't know if there was a poly limit) and reimported into Maya.

The result was just what I wanted, bar the bunching of the edgeloops at the top, although this does seem to so a good job at emulating the grain of the wood. My next task was to attach the single large leaf on the side of the roots. It was only at this point that I realised I would need more geometry to attach the cylinder like leaf stalk. I used the insert edge loop tool to add the require geometry and merged an 8 sided cylinder onto the appropriate area.

I then extruded and manipulated the cylinder into a stalk shape. I then used to create polygon tool to create the shape of one half of the leaf. I used the interactive split polygon tool to split the shape into quads. I then extruded and manipulated the leaf to give it thickness and a curve. I then lined up the leaf, duplicated it, deleted the required faces and used the merge vertex tool to attach the leaf to the stalk without moving the stalk vertices. I then repeated with the duplicated half of the leaf. I then realised that the leaf was too small and scaled it up by moving the pivot point to the side of the leaf closest to the tree to stop it scaling in the wrong direction.
I then needed to make the door itself. My first attempt was to again use the create polygon tool, split it into quads and then extrude and manipulate it into shape. However, this proved too messy and made the topology too uneven. I then used a box with 5 subdivisions along its height and width, Manipulated it into shape and moved it over to the door frame. It took a fair bit more manipulation to the the door to fit the doorframe well, fit the design and to be able to swing open without noticably passing through the frame.

With all the main elements made, the only things left to model were the smaller details. I made some mushrooms by extruding and scale faces on cylinders; and I made vines the same way, although I want to make one more.

I still have to deal with some bunched up edge loops caused by the extra geometry used to attach the leaf stem and some odd topology on the underside of the leaf. After this I intend on making one more vine, adding some planes for vine leaves and add some sort of ground, possibly with grass. Although I know that Maya can make grass simply using it's fur technology, I would rather use technology that could be imported into a game engine like Unreal. I may, again, use some upright planes onto which grass textures can be placed.