I have a lot of trees in pond baskets (like in your photo). I wouldn't say that putting them in those baskets speeds up growth, per se, as much as they reduce risk of root rot associated with over-watering, and they keep the tree from developing bad roots that often are the result of trying to grow trees in plastic nursery pots. If I REALLY want to speed up growth, I put trees in the ground. However not everyone has ground space to plant trees in for several years. In my case, I have had to move a couple of times in the last few years, which has prevented me from ground growing.
I have come to believe that a better alternative to using large pond baskets is to use Anderson flats. They are much larger, are shallower and flatter, and trees will grow much larger than if you kept them in a pond basket. I have some trees that have grown over 8' tall in an Anderson flat.
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