光周期（或光照周期表）是指室内种植环境中生长灯的程序化开启/关闭时间，表示为光照小时数后跟黑暗小时数（例如，18/6 表示 18 小时开启和 6 小时关闭）。光周期复制了自然日长模式，用于控制植物生长阶段——植物生长在长日照下维持，而许多开花植物在短日照下被触发进入生殖生长。
关键事实
- 18/6 or 20/4: standard vegetative growth cycle for most crops
- 12/12: triggers flowering in short-day plants (cannabis, some chrysanthemums)
- 16/8: common for most herbs, lettuce, and leafy greens — extends harvest window
- 24/0 (continuous light): used for some seedlings and microgreens; causes stress in some species
- Use a timer for consistency — irregular light cycles stress plants and can disrupt flowering
- Day-neutral crops (lettuce, most herbs) produce continuously regardless of light cycle length