Vegetation phenology greatly impacts urban development and climate change responses. However, research on phenological characteristics in small-scale urban areas is limited, especially concerning their spatiotemporal variations. This study analyzes the phenological indicators SOS, EOS, and LOS of urban vegetation in Suzhou from 2003 to 2022, utilizing Local Climate Zones (LCZs) and Urban–Rural Gradients (URGs) to explore their spatiotemporal variations and correlations with various LCZs and URGs. Subsequently, one-way ANOVA and the Honest Significant Difference (HSD) test are employed to compare the applicability of the two analytical methods. The results show that in Suzhou, SOS, EOS, and LOS exhibit trends of advancement, delay, and extension, with annual averages of 1.02 days earlier, 0.55 days later, and 1.57 days longer. Compared to land cover types, LCZ built types exhibit earlier SOS, later EOS, and longer LOS. As the urban gradient shifts from the city center to the suburbs, vegetation phenology shows gradually delayed SOS, advanced EOS, and shortened LOS. Additionally, phenological differences associated with LCZs are more significant and statistically relevant than those linked to URGs. The study confirms urbanization’s impact on vegetation phenology and provides new insights for future research. The findings assist in plant management, climate regulation, and living environment improvement, contributing to the sustainable development of resilient cities.