Over the past twenty years, landscape-scale green infrastructure planning has emerged as a way to support green spaces that provide ecosystem services and to revalue them in the planning and land development process. Despite the growth, there is little empirical research on the specific strategies that comprise local government green infrastructure planning and their success in supporting three important aspects of green space networks: size/shape, quality, and connectivity. This research fills that gap by examining how county planning agencies carry out green infrastructure planning and the effectiveness of county strategies in retaining, preserving, and connecting green space over time. The mixed-methods approach uses interviews and document review to create a framework for green infrastructure planning followed by remote sensing, GIS analysis, and a landscape ecology-oriented spatial analysis program (FRAGSTATS) to assess on-the-ground change in green space networks between 2000 and 2010. Results show that counties that incorporate many green infrastructure planning policies and strategies are more successful in retaining green space acreage, quality, and connections over time than those that use fewer. The facets of green infrastructure planning with the greatest potential impact on green space results are connectivity and growth management. The outcome suggests that counties interested in supporting green space networks should focus on policies specifically designed to support connectivity - such as purchasing land and development rights to create large contiguous blocks of protected forestland - and strategies oriented toward bounding growth, such as urban growth boundaries and restrictive rural zoning.