Solar-enabled thermal management is emerging as a promising candidate to exploit green, low-cost and efficient heat-related applications, which has drawn extensive intensity for the development of solar-to-thermal materials with high-performance and desirable functionality. However, there still remain considerable challenges, such as the sharp temperature fluctuations under water-related environment, high cost, complex fabrication approaches and limited energy efficiency. Here, superhydrophobic and photothermal nanostructured Janus membranes composed of hierarchical candle soot and transparent polydimethylsiloxane is proposed in a simple, low-cost, and effective way. The achieved membranes can readily adapt to curved surfaces and enable efficient solar-to-thermal capability of ≈68 °C under 1 sun and good water-repellant property of ≈159.7. Therefore, it can still maintain stable temperature without remarkable temperature decline when exposed to the high-moisture environment. Also, the asymmetric structure can further endow the membrane with declined heat dissipation for high-performance thermal management. Moreover, it can further function as a self-supported agricultural film to continuously heat the soils with stable temperature for efficient bean growth, demonstrating significant potential in the new generation of urban agriculture.