Isn't the Herb Garden in the Pot World full of medicinal herbs? Indeed... that's true. However, medicinal herbs require aging, and the ones preserved in the Pot World have experienced countless years, all being top-grade medicinal materials. To use them now for Green's alchemy practice would be a huge waste, like using a Thousand-Year Ginseng King to concoct an elixir for the common cold.
Green's abilities are still too weak. Even with herbs aged for tens of thousands of years, she could only harness the potency of hundred-year herbs, the rest would be wasted. To her current state, there's no difference between hundred-year and ten-thousand-year herbs; the elixirs produced would be the same.
