Wrap about one half the trunk of unbranched whips. Polyurethane spiral wrap for trees is easy to use and effective. Simply unwind the end and slip it around the base of the trunk. Then continue to fit it around the trunk. It will not blow off and does not require tying.
Polyurethane lasts for years and can be removed and used on another tree, at a later time.
Aluminum foil from the kitchen can also be used as a wrap, with shiny side out. Exposed heartwood from sunscald or a wound is an open door to borers and rot. Keep the trunk protected for two or three years, or until the bark becomes woody. Small, leafy twigs eliminate the need for wraps. When finally removing vigorous unwanted branches, cut them almost flush with the trunk or to a collar if the branch has one.