The complaints over drooping Endless Summer hydrangea are prevalent, especially if the plant is grown in too much sunshine. It does best in dappled sunshine, or at least protected from the hot midday sun. The plant will require irrigation during the heat of the summer.
Fertilize it in the spring when it leafs out and again one month later. Do not apply fertilizer after Aug. 1. Try mulching your plant with organic mulch to conserve moisture and keep the roots cool.