You want a lot of wood? You live on an island with 1 tree? Well, here is a way to make a tonne of trees. I found this trick while experimenting on P.E. on my friend's tablet.

Step 1: Cut down the tree and take all the branches.
Step 2: Wait till night falls and go to bed. The leaves left will gradually fall, some leaving saplings.
Step 3: Get the saplings and plant them around the Island.
Step 4: Use your method of growing them.
Step 5: When they grow, repeat from step 1.