AbstractThe proper irrigation of container plants is critical due to the limited substrate volume. This work investigated a zero-energy and self-operating drip irrigation instrument suitable for daily watering of container plants. The instrument consists of a partially filled, inverted solid container exposed to sunshine, and a large insulated one as the reservoir, which were connected hydraulically. This solar-thermophysical irrigation (STI) instrument operates through isobaric thermal expansion and contraction processes during both day and nighttime. The daily water discharge of the STI instrument was investigated experimentally and theoretically for different thermal conditions, pump sizes, and operating days. Field test results showed that the average discharge of this drip micro-irrigation device was 12 cm3/h in sunny climate. In a growth experiment, Solenostemon potted plants were irrigated via the STI instrument and 4-, 7-, and 10-day surface irrigation frequencies with identical water quantity. The results indicated that the STI system enhanced the growth traits of the plants compared with plants that underwent periodic irrigation. The novel STI drip irrigation system was appropriate for potted plants’ water demand, and was characterized by simplicity, passive operation, zero-energy, and microrate flow operation. The system can be used for individual plants and residential and small-scale applications.