You would need a tree creating skill to go with the infect/exploding skill.
There was a hero in the excellence contest that created pillars or something (the one with the passive that made them attack). Start from that.
Diseased growth : Place a diseased tree that deals a DoT around it. Has charges. The DoT stacks. No cooldown between placing trees.
It's good because you can also use it to cut people off.
The DoT needs to be strong, because of hatchet and runes. And all the skills that cut trees down.
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