[quote=@floodtalon]
Could the Green Relic affect the earth itself? Like tunneling underground for a quick escape. That would be Chen's plan, create a storm of leaves to obscure vision, grab Sí after tunneling underground and then get out of there. Meihou too if he believed he could.
[/quote]

The specific functions of the Green Relic are this: "This Relic grants the user accelerated regeneration in all forms, be it health, stamina, magic, and the like. It gives the user twin whip-blades."

The "earth manipulation" was just Chen healing the earth to the point of accelerated growth. Hence all the plants he could control.