There are reasons to install tree tubes over your young trees and reasons against. We chose to use some because we have deer that browse the top growth, thereby slowing the growth of the trees. The tubes are about $5 each locally if you provide your own post or stake.
I drive the T-post into the ground so the triangle anchor plate is in the soil. The tree tube is slipped over the seedling and secured to the T-post using wire ties. Be sure to leave the tube 3-4" off the ground so mice can't move in and overwinter in the tube. Very likely the mice will chew the bark off the tree, girdling it.
Once the tree has outgrown the tube you may want to remove it for use elsewhere.
Step 1: Removing the Tube
It is best to remove the tube before the tree develops sizable limbs that make easy tube removal impossible. The first thing you need to do is to check for paper wasps. They assume that the inside of the tube is their territory and will defend their turf if you try to mess with it. The dark spot near the center of the first photo is a small nest. I left this tube in place.
For a sapling without upper limbs simply remove the wire ties and slide the tube up and over the tree. For trees with substantial limbs you can slit the tube top to bottom. Take another quick peek to make sure there are no wasp nests. Remove the tube and save it for another Instructable I may do on reusing slit tubes.
It has grown in a protected environment so the tree may not be strong enough to support itself in a strong breeze. Until the tree can become stronger I use the post as support. Slip a plastic jar over the top of the T-post and loosely secure the tree to the post with a wire tie. Check the tree frequently to make sure the tie isn't damaging the tree. If it is, replace the wire tie with rope at least 1/4" in diameter. Make sure the rope can't just slide down the post and tree by securing it to the post with a wire tie. The jar is to protect the tree from the top edges of the post. The 4th photo shows a tree healing from the damage done before I started using protective plastic jars. Once your tree is about 3 to 3-1/2" diameter near the base it is probably safe for the tie and post to be removed.
One of the main causes of death for trees in yards or other maintained areas is debarking by lawn mowers or string trimmers. Wherever we have trees that might be injured by lawn care machines I install a protective plastic collar at ground level. A cheap collar can easily be made from a short section of corrugated drain pipe. A 4" x 10' piece is less than $5 at many DIY stores. Cut off an 8" section with a utility knife or use a hand saw. Slip it over seedlings or cut up one side with tin snips for installation on larger trees. Work the tube down to ground level so trimmer strings can't get under it and damage the bark of your tree.