Wesaelan Brookshadow in The Elddar Grove will ask you to locate the Old Oak Tree in Antonica (in middle of fields right outside of North Qeynos gate at -93.68, -19.70, 119.12 ). This is the first in a multi-stage quest.
Latest reports are when you do locate it, the brigand leader will spawn by himself. It no longer seems to matter if the quest is grey to you.
After you've completed the tree quest you need to return to Wesaelan in The Elddar Grove. This opens up the Recovery of the Bloodsaber Plans quest.
I've been sent to retrieve an old tome from a tree where druids of the god Karana hid it over a century ago. I'm to find the tome hidden in an ancient oak tree in the middle of the fields just outside of Qeynos.
I've been sent to retrieve a tome from a giant oak tree in the crop fields outside of Qeynos.
I must retrieve the tome from a giant oak tree in Antonica.
I've retrieved the tome from the oak tree in Antonica.
I've recovered the tome from a group of brigands that ambushed me at the oak tree.
I must return to Wesaelan with the tome I retrieved from the corpse of the brigand leader.
I must speak with Wesaelan and give him the tome.
I've spoken with Wesaelan about the events that transpired.
I've spoken with Wesaelan about the events, and given him the ancient tome.
Strangely, I was ambushed by brigands just before I could reach the tree mentioned by Wesaelan. There must be a spy within the ranks of the druid order in the Elddar Grove, for there is no other way I can think of that they could have known I would be coming.