One of the most important management considerations for hydrangeas is avoidance of hot, full sun planting sites.  According to a 2008 research report from the University of Tennessee, "Shading densities significantly affected disease severities of Cercospora leaf spot on bigleaf hydrangeas.  In general, lower disease severities were associated with higher shading densities.  Disease severity in full-sun and a low degree of shading could be associated with stress associated with less vigorously growing plants in high light intensity conditions."   Pictured below are several Hydrangea macrophylla 'Dooley' growing under perfect light conditions at Brookgreen Gardens, SC on June 5.  While it's always possible for at least some

Cercospora leaf spot to sneak into a hydrangea planting by late summer, shady conditions should prevent disfiguring levels of damage.