Forest SiegeSource Occult Origins pg. 8
Element wood; Type utility (Sp); Level 9; Burn 0
You can transform available plant life into a besieging army. This functions as greater siege of treesUC, except you need to concentrate or the effect ends, and you can change targets as a free action. If you accept 1 point of burn, you can prolong the effect without the need for concentration until the next time you recover burn, but you do need to spend a standard action to change targets.