Thank you for your question. Your hydrangea appears to be a H. macrophylla, and you can prune now, but may cut away some of next year’s blooms. New growrh can be either blooms or lateral stems. Here is an Extension article from OSU: https://extension.oregonstate.edu/gardening/flowers-shrubs-trees/general-care-hydrangeas and here is another more expansive resourse: https://ucanr.edu/datastoreFiles/268-86.pdf Hope these are helpful. Good luck!