Rosemary is a versatile Mediterranean shrub valued for its culinary and medicinal uses, also finding applications as a food additive (E-392). This study explores the potential of rosemary for large-scale cultivation as well as the valorization of its distillation residue, which constitutes more than 95% of the total biomass. Rich in bioactive compounds, this solid waste represents a valuable opportunity to develop renewable plant-based products. This study monitored the agronomic adaptations of cultivated clones of rosemary and evaluated the essential oil and phenolic content. This study also evaluated the biological potential of the ethanolic extracts from the distilled residue as an antifungal, antioxidant, chelator, and biostimulant in model tests. Interestingly, the extracts showed substantial phenolic content, exhibiting strong antifungal activity, antioxidant capacity, and efficient metal chelation. Furthermore, all extracts also demonstrated promising biostimulant effects on rooting. Among the clones evaluated, Pina de Ebro stood out especially for its balanced adaptability, high essential oil yield, and outstanding phenolic content, along with uniform biological capacities among individual plants and plots. Therefore, this study highlights the potential of utilizing the entire rosemary plant, enhancing the overall profitability of the crop and meeting the growing demand for eco-friendly and renewable resources in the market.

There is a growing demand for sustainable crop strategies that reduce the use of agrochemicals while improving productivity. This study investigates distillation residues of Salvia rosmarinus to develop a novel biostimulant with enhanced antifungal activity, together with natural additives that ensure homogeneity and water dispersibility. Accordingly, several residual by-products released from agroforestry processes and regarded as “plant protection products” were evaluated in phytotoxicity tests in seeds of Lactuca sativa and Lolium perenne. The tested substances included solvents (ethanol, glycerol, propylene glycol, and DMSO) and adjuvants (soy lecithin, polysorbate-20, acetic acid, and ascorbic acid). Those showing the lowest adverse effects were combined with the extract following a 3² factorial design. Most formulations exhibited good water dispersibility and significantly enhanced the germination index of Lactuca sativa, while simultaneously reducing the growth of Lolium perenne and the fungus Aspergillus flavus, all in a clear dose–response manner, as suggested by the four-parameter log-logistic (log₁₀(x)) models. These results indicate that both stimulatory and inhibitory effects were strongly influenced by concentrations, highlighting the importance of optimizing application doses. Among the evaluated carriers, the one lacking glycerol and containing high ratios of polysorbate-20 and soy lecithin demonstrated the most balanced overall performance in terms of physical stability, dispersibility, and biological activity, a response that can be attributed to the combined contribution of the extract and the selected carrier components. Overall, this study demonstrates that bioagrochemicals derived from agroforestry by-products can provide dual-function agricultural applications (biostimulant/antifungal or herbicide/antifungal), while supporting the framework of the circular bioeconomy.