A simple method for propagating hydrangeas and certain other shrubs is by soil-layering, a method that can be used from April through fall.
Choose a limb close to the ground. Press it downward until the stems touche the ground. At the point where the branch touches the ground, scratch the stem (wound it) to expose the inner bark. This is where the roots will develop. You will get even better results if the point of contact also has a node (the part of the stem where shoots, leaves, or buds emerge). Cover the wound (not the entire limb) with soil, the richer the soil, the better results you can expect. Place a brick or rock on top to hold the branch in place. At least 6 inches of branch tip and leaves should be showing beyond the brick. Keep it watered, don't let it dry out. In two months, tug gently to see if roots have formed. If there are substantial roots, cut the new plant from the mother plant. If there are only a few roots, recover with soil and check again in another month.Hydrangea
Photo by Larysa Johnston