I have pulled about 2-3 dozen tree tubes from around White Oaks that I planted in them 4-6 years ago.
The problem I had was some of the trees had grown good for 2-3 years then the top of the tree, the last 1-2 years of growth dies.
The tree then resprouts from below.
Not all did this in fact some of the Oaks are out of the tubes anywhere from 1-5 ft.
So after pulling the tubes I put 2" x 4" x 5 ft tall wire fence around them. I made the fence into a 2 1/2 ft dia tube.
Next summer will tell the tale if the trees pop back or continue to decline.
All these trees were planted in woodland openings that were made when a tornado that went thru.

Now I have a bunch of tree tubes that I need to get rid of, if anyone is willing to pick them up they can have them, they are all 5ft tall.

some pictures

A White Oak about 5-6 ft above the top of the tube growing great.



growing from the bottom, you can see last years dead leaves on the top that have stayed on the tree for over a year now.

May be too much shade (from the canopy-not the tube).

I have tubes on some 150 oaks , no problems yet, lots are out the top of the 5 foot tubes, do you have oak wilt in your area ?

Too many different bugs killing oak trees today. I've lost about half my old growth oaks. They just die. Google what's killing oak trees.

I think this. Oaks are a disturbance species that need sunlight. I'm about to pull a lot of my tubes as well on the trees that made it.

Down here, fireants have become a big obstacle for tree tubes. Rather than mounding, they have learned to burrow up and build within the tubes putting dirt all over the trunks of the young trees; which will kill the tree.