Willow (Salix sp.) is an effective phytoremediation and lignocellulosic bioenergy crop. Phenolic yields (kg ha−1 yr−1) were quantified in 5 willow cultivars at 4 sites. Significant and substantial variation was observed in different phenolic groups. High phytochemical yields can improve economic feasibility of sustainable biomass. Integration of green technologies can alleviate multiple environmental problems.