Northlawn Flower Farm and Gardens shows how to turn one hydrangea into many, for free, using nothing more than a few cuttings and a jar of water. If you're already out there with pruners, this is the tutorial that puts those trimmings to work. It's a hands-off method that suits busy gardeners and total beginners, and the plant does most of the labor itself. One quick note from the video: only propagate hydrangeas that are not patented.
The plan is simple. You take softwood cuttings in early summer, trim them down, and root them in water while you go about your week. A few weeks later, white roots appear, you pot each cutting up, and by the following year you've got baby shrubs with their first blooms. There's no fancy gear and no daily fussing. Just snip, trim, and wait.
Propagating is not the same job as tidying up an overgrown plant. If you're here to shape and cut back, our guide to pruning hydrangeas covers that, and the good news is that the trimmings you'd normally toss can become new plants with this method. Once you're hooked on free plants, the same idea works for houseplants too - see how to propagate pothos and how to repot a plant for the next steps.
The steps above are specific to this plant. The general method - where to cut, stripping leaves, rooting hormone, soil versus water, and how to divide plants that will not root from a cutting - is at how to propagate plants.