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Trichoderma is a widely recognized plant-growth-promoting fungus that has been extensively utilized in various agricultural applications. However, research on the economic production of Trichoderma spores and their effects on tea cuttings must be further advanced. In this study, T. guizhouense NJAU 4742 (NJAU 4742) emerged as a growth-promoting strain for tea cuttings, and the spore-production conditions of NJAU 4742 attained through solid-state fermentation (SSF) using tea residues were optimized. In a pot experiment, nursery substrates containing different concentrations of NJAU 4742 spores were tested for their influence on tea cutting growth and the rhizosphere fungal community. The optimal conditions for spore yield were determined as a 7:3 (w/w) ratio of tea residue to rice bran, a material thickness of 3 cm, an inoculum concentration of 15% (v/w), and an incubation time of 4 days, resulting in a spore count of 1.8 × 109 CFU/g. Applying NJAU 4742 spore products significantly increased the biomass of tea cuttings and influenced the fungal community composition. Moreover, higher concentrations of NJAU 4742 spores yielded better growth performance, and applying nursery substrate with 1.0 × 107 CFU/mL spores was the most economically viable option. Notably, among the top ten fungal genera with the highest relative abundance, Trichoderma showed a positive correlation with the fresh weight of tea cuttings, while the others exhibited a negative correlation. Overall, utilizing tea residue for SSF to produce NJAU 4742 was a feasible approach, and the application of NJAU 4742 spores enhanced the growth of tea cuttings by increasing the relative abundance of Trichoderma. [ABSTRACT FROM AUTHOR]