Good Morning Cynthia, 

Thank you for contacting the U of M Extension Service. 

From viewing your photo, it appears your hydrangea is attempting to sprout in between the old branches. I would pull the mulch away from the base of your shrub and prune back the dead branches to allow more air movement around the base. 

Here is a link from the U of M Extension Yard and Garden website: https://extension.umn.edu/planting-and-growing-guides/pruning-hydrangeas-best-bloom  all about pruning your hydrangeas. 

Good Luck!