How to propagate hydrangeas from cuttings - Removes all leaves except 2 at the top and cut these half crosswise, dip the base in to a rooting hormone and plant. Water well, and cover with plastic bags, making sure the plastic does not touches the leaves. The cuttings should root with 2-4 weeks.
HOW TO TAKE HYDRANGEA CUTTINGS |The Garden of Eaden
Rooting hydrangea cuttings: Hydrangeas respond well to several propagation techniques, including layering and dividing. But rooting softwood cuttings in summer will yield a bunch of new plants in about four weeks.