Leaves and other debris can carry fungal diseases as well as insect eggs from one season to the next. Diseases and insects can both negatively affect your upcoming season of flowers.
If your hydrangea has not bloomed for an entire season and it looks like it may not bloom again this year, consider if you are growing a hydrangea species that is suitable for your zone.
Aside from spring fertilization, you don’t need to go crazy fertilizing. If you have already overfed them, you may have hindered their flower formation. Hydrangeas do not need an intense fertilization schedule.
Mulch serves multiple purposes. The first of course is cosmetic. A freshly mulched garden is an easy way to add curb appeal.. The second is for water retention. Mulch itself absorbs moisture, and it helps hold moisture in the soil.