Display omitted •Populus alba waste leaf material could be an opportunity in technological fields.•Poplar was intercropped with walnut and three ancillary species.•Poplar leaves showed good anti-radical activities, content of lignin and phenols.•Mass spectrometric analysis showed that intercropping affects metabolic profile.•Elaeagnus umbellata made antiradical activities and phenols content to decrease. The growing need for biomass recovery suggests forest waste leaf material for technological applications in a circular economy scenario. In this context, white poplar (Populus alba L.) foliar material was recovered in a forest site planted on a former agricultural land was identified in Tuscany (Italy), and intercropping eventually occurred was also valuated. In fact, the mixed plantation was characterized by tree different associations consisting of broad-leaf trees, including Populus alba L. intercropped with another valuable species (walnut, Juglans regia L.), and different nurse species (Italian alder, Alnus cordata (Loisel.); hazelnut, Corylus avellana L., Autumn olive, Elaeagnus umbellata (Thunb.)). Thus, Populus albaleaves were investigated for their lignin and phenol content, and for their anti-radical activity by (2,2-diphenyl-1-picrylhydrazyl) DPPH and 2, 2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) ABTS assays. Furthermore, Populus alba extracts were profiled by liquid chromatography hyphenated to high-resolution tandem mass spectrometry (LC-HRMS/MS), in order to deepen into the intercropping influence on specialized metabolites’ content. In particular, it was observed that when Populus alba grows in presence of the nurse species Elaeagnus umbellata, a decrease in the aforementioned parameters was observed, as well as a negative impact on the polyphenol profile. Thus, our findings are in line with the observation that white poplar leaf residue has a high potential for achieving bioactive polyphenol compounds, and that an intercropped nurse species such as Alnus cordata could favourably augment flavonoids and chlorogenic acids to be used as multifunctional ingredients.