Trichoderma spp. are widely applied, eco-friendly mycofungicides and plant growth promoters. Native Trichoderma strains are likely to have more productive, stable biocontrol and biofertilizer activities since they are well adapted to the local environment. In this study, we isolated a native Trichoderma strain ‘Th62’ from the rhizosphere soil of wild Chelidonium majus plants in Harbin, China (126.6341°E, 45.7242°N). The isolated Trichoderma strain was identified as a T. harzianum strain via morphological observation and molecular methods based on the rDNA internal transcribed spacer region and elongation factor-1α gene sequences. Significant antagonistic activities of Th62 against five soil-borne fungal phytopathogens, Fusarium oxysporum, Sclerotinia sclerotiorum, Alternaria alternata, Cytospora chrysosperma, and Rhizoctonia solani, were confirmed by dual-culture assays. Furthermore, the crude fermentation products of Th62 also displayed antifungal activities against these five pathogens. To evaluate the function of Th62 as a biofertilizer, we subsequently applied Th62 on cockscomb (Celosia cristata L), a plant species with both ornamental and medicinal values, by inoculation with Th62 conidia at different concentrations, 1 × 10¹⁰ cfu mL⁻¹, 1 × 10¹¹ cfu mL⁻¹, and 1 × 10¹² cfu mL⁻¹. The beneficial effects of Th62 were evaluated by measuring the growth and photosynthetic traits of the inoculated cockscomb plants, and the results demonstrated that Th62 significantly improved the photosynthetic efficiency, photosynthetic capacity, and the adaptability to intense light of the inoculated cockscomb plants compared to the controls. Consistently, Th62 inoculation significantly improved the growth and flower yield of cockscomb. We presented a positive case of isolating and applying native microbial resources on local plantation practices.