The Greatwood is a tree added by Thaumcraft 4. It is a tall tree with a 2x2 trunk. Its logs can be crafted into Greatwood Rods to create wands. Every 1 out of 8 Greatwood Trees spawned naturally in the world is inhabited by spiders; the Greatwood Tree is covered with Cobwebs and a Cave SpiderMonster Spawner is placed underneath the stump, with a Chest containing randomized loot underneath it.
Its logs and planks are considered transparent and as such cannot be attached to fences or complete Redstone circuits.