Which do you think is better Will? Ground or Pond Basket?
I'm going to play devil's advocate here: Did you take the time to read the article on the subject although it was addressed to someone else? or did you merely jump in at the end of the thread.
It gets frustrating posting the information over and over again. This is understandable as folks arrive on the bonsai scene weekly. However, a lot and time and effort goes towards putting these articles together so all can benefit down the road. It becomes an avenue to answer enthusiasts questions without having to type "the entire answer" all over again. What is appreciated is when folks take the time and read the info and then, request clarification on the subject if needed.
From cradle to grave...
The tree starts out as a seedling, gets potted to a 2 inch pot, then the following year gets placed in the ground until the desired trunk thickness is achieved:5, 10, 15 years plus. During this time judicious pruning is carried out to developing branches to basically design/shape the tree. After the initial 5 years the tree gets uprooted and repositioned in the grow bed, so that it gets even distribution of sunlight (more on that later). Here, the tap root is removed (if not already done) and some root work can be carried out.
Once the trunk has reached the size wanted, and depending if the root work is complete, the tree gets planted out in a grow box for further refinement. The advantage of this method (a continuation method) is that the grow box can be rotated rather easily to ensure sunlight gets to all parts of the tree. A further benefit of the boxes because they are made of wood is it is easy to use guy wires with them as they have multiple anchor points (basically the entire box). This also permits the tree to become accustomed to life in a pot.
IN order to proceed (most times) to a bonsai training pot (larger than necessary bonsai pot) the tree gets placed in a pond basket, screen sided container etc... to develop the small feeder roots necessary for life in a bonsai pot. The tree remains there until sufficient fine feeder/radially growing roots are available to permit sustainability in a bonsai pot. You can develop roots in a bonsai pot by chasing back on subsequent repottings, but air pruning a la pond basket gets you there quicker.
Depending on the care the tree has received in the ground (roots), grow box, and pond basket. The tree's root pad may be reduced sufficiently to fit in a bonsai pot of appropriate size. However, this is never really the case and the size of the pot will need to be reduced over time to the "correct" size pot.
It takes roughly 2 years for a tree to (root colonize) in it's environment (regardless of that environment), the 3rd year they really take off. The longer you can leave them be, the faster you can get there. Bonsai pots are used for the "final" stages of development "refinement". It is at this time that the characteristics of slower growth are desirable in order that the bonsai becomes more manageable.