Laboratory-scale experimental results suggested that phenol degradation by vetiver involves two phases: Phase I, phytopolymerization and phytooxidation assisted by root- produced H2O2 and peroxidase (POD), followed by Phase II, a combination of Phase I with enhanced rhizomicrobial degradation. The first 360–400 hours of phenol degradation was dominated by phytopolymerization and phytooxidation. Phenol was rapidly detoxified via transformation to phenol radicals, followed by polymerization to non-toxic polyphenols or regioselective polymerization with natural organic matters prior to being precipitated as particulate polyphenols (PPP) or particulate organic matters (POM). After this first phase, phenol decreased from 500 mg/L to around 145 mg/L, while PPP and POM increased, as indicated by the increase of particulate chemical oxygen damand (COD). Synergistically, rhizomicrobial growth was ~100-fold greater on the roots of the vetiver grass than in the wastewater and participated in the microbial degradation of phenol at this lower phenol concentration, increasing the phenol degradation rate by more than 4-fold. This combination of POD-assisted phytopolymerization, phytooxidation, and rhizomicrobial degradation completely eliminated phenol in the wastewater in less than 700 hours.