The Greatwood Sapling comes from the Greatwood Tree added by Thaumcraft 3.

How to make a Great Wood TreeEdit

To grow a Great Wood Tree you will only need 1 sapling to grow the tree even though the tree has a 2x2 base. For the tree to grow the blocks to the south, east and south-east need to be clear and you cannot use bone meal to grow the tree, instead, use the hoe of growth.

Where to find these treesEdit

These trees spawn in areas where there is high vis *note these trees spawn during chunk generation, if you create an area with high vis manually they will not spawn, you have to plant them* if you are looking to get into Thaumcraft setting up a base around these trees is a good idea.

Greatwood trees, unlike the Silverwood tree, do NOT need nearby aura nodes in order to grow new ones.

Sometimes naturally generated Greatwood trees will spawn coated in several spiderwebs. Approach with caution as a family of cave spiders has taken to this tree... although a chestful of loot will be yours should you disturb their nest. (A chest full of loot is below the spawner, which is under one of the bottom log blocks)