He has two abilities. One is called Death Blossom. Flowers will sprout from the ground and chase the target. When they reach the target, a very large undergrowth will erupt from the ground. The other ability makes the tree plant its roots into the ground. While the roots are in the ground, the tree can't move. But, it will spawn scorplings that you can use to attack the enemy. The treature is a unit that has high health.
Scorplings have a medium speed, low health and low attack. They can be upgraded to have 2 bars of health versus the standard 1. Then they can be upgraded to acquire a poison effect.
One common tactic is to mass Treatures and have them sit at the pillar with their roots in the ground. This allows for armies of scorplings to be spawned from the midddle at no cost. Spirit pillar helps lots. If enemies try to charge the treatures, death blossom can be used. Airs can be used to take out Charrogs or you can try death blossom.