This guide explains how you can grow dark oak trees. Easy to understand method is discussed below to complete this task.
In order to secure dark oak saplings, you will need to put it down for your bone meal.
Dark Oak wood is a bit different to grow. You need to put down 4 of them in order to grow because they are not considered as a single tree. Pick up an axe and start cutting the tree.
The drop rate of these is not good, so you have to make sure to find the real area where you got them. You can create a whole new forest of oak trees as shown in the image below.