The characteristics of Fe3+ being easily accessible, cost-effective, and environmentally friendly make it the most cost-efficient activator for phosphors in phosphor- converted light-emitting diodes (pc-LEDs). The intrinsic luminescence of Fe3+ is spin-forbidden and parity-forbidden, resulting in extremely low luminous efficiency. The exposed 3d5 electrons are highly sensitive to the crystal-field environment, and its luminescence characteristics strongly depend on the symmetry and vibration modes of the host lattice. In this paper, (Y2.93Lu0.07)Al1.03Ga3.999O12:0.001Fe3+ ((YL)AGG:0.001Fe3+) phosphor that can be excited by commercial blue-light chips was synthesized through cation substitution (Y3+/Lu3+) in the garnet-structured Y3AlGa4O12 matrix and the addition of excess Al3+. Cation-site engineering reduced the symmetry of the crystal - field environment where Fe3+ is located, partially lifted the parity-forbidden of the electric-dipole transition of Fe3+, and increased the luminous efficiency of Fe3+. Its emission wavelength (600-850 nm) and emission peak (711 nm) precisely cover the deep-red (660 nm) and far-red (730 nm) regions with high absorption by plant pigments, and also increase the near-infrared band beneficial to plant growth. At 423.15 K, the thermal stability of this phosphor remains 97.33% of that at room temperature. A pc-LED prototype was fabricated by integrating this phosphor with a commercial blue-light chip, and its potential application in the field of plant growth was demonstrated. This work provides a new option for the development of pc-LED phosphors for plant lighting with Fe3+ as the activator and a new generation of compact light sources for plant lighting.