What some think is good for a tree can be what actually kills a tree.
Protecting the trunk of a tree is important for all young trees. The young bark transports minerals up from the roots. It is very important to prevent this bark from being damaged so that transport can take place.
If mice or other rodents or rabbits eat off the bark all the way around the trunks of young trees, they will eventually die. If the bark is damaged by lawn mowers or weed eaters, the same thing can happen. If the bark is damaged only partially around the main trunk, it will heal the tree will continue to grow.
A classic way that you can protect the bark on young trees is to wrap the trunks with a 2-3” wide strips of metal screening or hardware cloth. Start at the bottom just under the soil surface and wrap up two to three feet up, or to the first set of branches. The beauty of using screen or hardware cloth is to allow the bark to breathe and rain and snow to dry quickly. You can leave it on the tree if the trunk is not being restricted from expanding so it may have to be loosened as the tree grows. Check each year to be sure it is loose enough.
Another method is to use tree guards that are available in many places. The important thing to remember to select light colored guards so during the winter months the trunks do not heat up which can kill the tree. Black drain tile is not a good option please.