Root Thresher can be found in Azuremyst Isle [33, 37.8].
0.05% Chance of a common drop.
0.26% Chance of a poor drop.
Note: % drop chance was correct at the time the page was generated/created. This will not be updated.
According to Daedal of Azure Watch, in the quest  An Alternative Alternative, the Root Threshers consume Azure Snapdragon Bulb for sustenance.