Don't use wood containers for trees!
Obviously common sense should tell a person (me) that this is not a good idea. So today I went to remove a sweet cherry growing in a whisky barrel so I could give it away (don't need it)... The bottom was more or less rotted away (roots had grown INTO the wood) ..i. was able to peel everything off by hand. All the wood touching soil was rotted away and i could snap them in half with my hands (these things are oak i believe)... So yeah...this was 4 years of use and its dead now. I have 2 other trees in them that will be getting new homes soon. Stick with plastic.