The New Adventures of Jonny Quest (1986)

S1E12 Creeping Unknown

A mysterious plant-based entity is behind the vanishing of several individuals in the neighboring forest, and the Quests must confront it before it expands its reach. To their horror, they learn that the creature transforms its victims into identical plant beings, leading to the emergence of a growing legion of these vegetoid creatures. Time is of the essence as the Quests race to stop the impending threat.