Best way to take cuttings of Sambucus nigra is as hardwood cuttings in Late October/November. Choose one year growth about a foot or so in length and simply use a spade to open a 'V' in the ground and place four or five leafless stems in to about half their depth the right way up of course. Gently push the soil back against the base of the cuttings. By spring, the cut end will have calloused over and be producing root tissue. Leave until the following autumn and plant where needed.