The roots of the Mother Tree.
A Mother Tree is the enourmous matriarch of Stickmen, in whose shadow they live out their lives. It may be that, to survive, Stickmen may never wander far from her. A Mother Tree does not appear to be sentient. It is possible that all female Stickmen are Mother Trees.
The Mother Tree of Wick, Willow and Woody that April encounters on Alais is at least many hundreds of years old. She has a Lunar Cannon in her branches which April uses to gain access to Tama'a.