After four decades of fierce urban growth driven by economic development, China recently adopted a ‘three red lines’ policy to protect its permanent farmland, vital ecosystems, and to contain urban expansion. To delineate urban growth boundaries (UGBs), current methods all employ quantitative land-use suitability indicators to define a compromise between competing spatial claims. However, ignoring site characteristics and underpinned by an increasingly dualistic conception of the urban and the rural realms, these methods often result in divisive UGBs devoid of any spatial quality. This paper explores how UGBs, rather than passive borders, can be designed as context-responsive and integrative urban-rural interfaces. A brief description of the urban growth phenomenon and the authorities’ responses at the national level is followed by more specific investigations in the Yangtze River Delta (YRD) region. Six representative urban-rural edges are examined in terms of historical development, planning, policies, current challenges, and opportunities. Based on the analysis, alternative design strategies are proposed to refine the definition of UGBs from a perspective of spatial quality and programmatic innovation. A final part discusses how the design explorations in the YRD can be systematized as a qualitative context-responsive method for UGB planning in China.