Wood distillate (WD) is an environmentally safe bio-based product stimulating plant growth and yield and allowed in Italy in organic farming. To the best of our knowledge, there are no studies on the effects of WD on spontaneous plants growing among crops, including their functional traits such as biomass. To test such effects, we carried out a lab experiment on artificially reconstructed arable plant communities composed of five species of conservation interest, which are specialist winter cereal crops: Bromus secalinus L., Centaurea cyanus L., Lathyrus aphaca L., Legousia speculum-veneris (L.) Chaix, and Scandix pecten-veneris L. After sowing 45 pots under controlled conditions, we applied WD at three concentrations (0%, 0.2%, and 0.5%) six times over 7 weeks. The number of emerged plants in each pot was counted every two weeks. Finally, we harvested all plants and measured the fresh and dry above-ground weight of each species in each pot. The resulting data were analyzed by Permutational Analysis of Variance. The application of 0.2% and 0.5% WD modified the community composition after two weeks, but such differences later disappeared. Both 0.2% and 0.5% WD had a positive effect on the dry weight of S. pecten-veneris and a negative effect on that of L. speculum-veneris. Moreover, 0.2% and 0.5% WD increased seedling emergence in L. aphaca, and 0.5% WD increased seedling emergence in S. pecten-veneris. Both 0.2% and 0.5% WD enhanced seedling emergence in the entire community. We suggest that the use of WD at low concentrations in winter cereals may be a sustainable agricultural practice that benefits crops without harming the associated plant diversity.