I plan on planting my 3 year old root ball in a container. How big of a container should I use? Should I look for wide containers (cheap home depot plastic storage bins) or deep ones (garbage can)?
Out of the two, I would pick a garbage can over a plastic storage bin. They have a big taproot and spread all the way down that. A third year I would say a 13 gallon garbage can at the smallest.
I would go deep. I had my first years in a 25 gal container last year that was maybe 24" wide and 16" deep. The roots easily "drilled" down through the middle (for the most part) and actually out the bottom of the container where drainage holes were and into the ground.