There was indeed a trap here.
The existence of the Ancient of Lore in the Grey Valley Stronghold was not a secret. When Lu Li was guarding the Black Sea Coast before, he had entrusted Grey Valley to Wandering. There were two trump cards. The first was the walls of the Stronghold and the second was this Ancient of Lore.
While this tree's body was rooted within the walls of the Stronghold, its skills were able to strike outside the walls.
Therefore, a conclusion was reached that the Ancient of Lore's range was covered a wide radius. Furthermore, this could mean that there were a tremendous number of Treants providing materials for the Ancient of Lore. Only these Treants could summon so many Saplings.
The first hypothesis was correct. The range of the Ancient of Lore was indeed rather wide and was still able to extend even further. The final extended range could be enough to cover the whole map.