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Commercial cellulase production has increased in recent years and consistent research has been carried out to improve levels of beta-glucosidase. Bioprocesses have been successfully adapted to produce this enzyme, with solid-state fermentations as the best-suited technique involving fungi. The aim of this study was to use leaves of tarbush (Flourensia cernua), an abundant shrub of the Chihuahuan Desert, as a carbon source for beta-glucosidase production by Aspergillus niger. During the solid bioprocess, this enzyme reached its peak production at 36 h of culture with 3876.6 U/L. There is a particular interest in the substrate composition because of the possibility of phenolic glycosides having an important role in beta-glucosidase production. HPLC-MS analyses showed that glycosides were present with the highest accumulation at 36 h of fungal culture. Luteolin and apigenin glycosides [1.8 and 2.4 absorbance units, respectively] were also detected and showed their highest point of detection alongside the highest beta-glucosidase activity. No apparent changes in cellulose were observed, while hemicellulose content decreased, which could be related to production and activity of beta-glucosidase. This study shows that leaves of F. cernua are an important raw material for beta-glucosidase production and give a source of compounds of added value which also may have an important role for beta-glucosidase production.