Worth watching the entire half-hour, because the time you spend here, becoming well informed about girdling technique, is much less than the time you waste if you do it wrong and have to keep on fixing your mistakes or watching all your work fail. Key points: 0:00 background info about invasives 6:20 girdling: types of knife 8:15 science: why girdling works, and important understanding of tree anatomy 12:15 technique, initial cut 17:00 why not do to vertical incisions 18:20 technique, peeling 20:00 technique, cleanup of the cambium 25:00 on followup 25:30 more details: target selection, branches, height