How to propagate hydrangeas
Start with a fresh green stem, taken in spring or early summer. If you haven’t done so already, deadhead the flowers down to where you get living stems.
Cut healthy pieces of stem about 15–20cm long, positioning the top cut above a pair of emerging leaves, close to the node, and the bottom cut also just above a node.
If lower leaves are mature, remove all but the top 2 and cut these in half to reduce water loss as roots eventually begin to form.
Dip the cuttings into rooting hormone gel or powder and insert into pots filled with propagating mix so about a third to a half of the cuttings are buried.
Water well and put pots in a protected spot, out of direct sunlight. Keep your cuttings moist but not soggy.
Roots should emerge and be strong enough for transplanting to your garden or another pot in about a month.