Plant water use can have a profound impact on the regional water cycle and water balance. A great deal of research has been conducted in this area in recent years. However, plant nighttime sap flow and non-growing season water use have rarely been addressed. These two components should not be neglected in accurately predicting the water use of urban landscape trees and large-scale plantation forests. In this study, the thermal diffusion probe (TDP) method was used to observe the water use of Fraxinus pennsylvanica Marshall, a common tree species in northern China. Continuous observations of sap flow were made from November 2020 to September 2021, while meteorological conditions in the region were recorded. We analyzed the sap flow changes in different months and their responses to environmental factors at the daily scale. The results showed a clear circadian rhythm phenomenon of sap flow during the growing season, with strong correlations between nighttime sap flow and daytime sap flow, as well as environmental factors. Transpiration and refilling stem water storage were also observed at night. In the non-growing season, the average whole day sap flow rate is less than 0.5 cm/h. The difference in average sap flow rate between daytime and nighttime is less than 0.3 cm/h. At the daily scale, temperature (Ta), relative humidity (RH), and vapor pressure deficit (VPD) were the main influences on nighttime sap flow. Solar radiation had a significant effect on the overall water use strategy of the trees.