Undergrowth first appeared in "Urban Jungle". Angered that the people of Amity Park were destroying his children for urbanization, he attacked and used mind vines to turn everyone into his slaves. With Sam turned into his "daughter", he had her attack Danny.

However, Danny managed to escape with his new ice powers. Sometime later, Danny returned, having finally mastered his ice powers thanks to Frostbite. Using it, he managed to destroy Undergrowth's new plant world by defeating Undergrowth. However, he was only reduced to a shrub but destroyed by Tucker's lawn mower when he voiced an attempt to restart the chaos.

He has a cameo in "Boxed Up Fury", in which the Box Ghost finds a reward for Undergrowth, claiming that he's an overgrown fichus.

Undergrowth's next and final appearance was in "Phantom Planet". He first appeared earlier, when Danny battled him in an attempt to prove his superiority to the "Masters' Blasters", only to fail and for them to capture Undergrowth.

Undergrowth later appeared as one of the millions of ghosts who agree to help Danny save Earth from the Disasteroid.