Found this useful little tidbit about transplanting on Washington State University's webpage about "Horticulture Myths", actually there is alot of good reads on here, originally linked in another one of UB's posts, Thought I'd share the knowledge!!!
Though gentle handling of roots is good advice when transplanting seedlings, especially annual flowers
and vegetables, woody perennials, shrubs, and trees all benefit from a more vigorous approach. There are
several reasons for this, and surprisingly some of the harshest techniques result in the healthiest plants.
Containerized materials, especially those in gallon sized pots, often have serious root problems as a result
of poor potting-up techniques. Potbound plants exhibit circling root systems, which if not corrected
become woodier and more troublesome the older they get. Eventually these circling root systems become
girdling roots, which can lead to the early death of otherwise healthy trees and shrubs. At transplant
time, a more aggressive approach to root preparation can discover potentially fatal root flaws. Circling
roots, J-hooked roots, knotted roots, and other misshapen roots can often be corrected by careful pruning.
In this manner it’s possible to remove those root problems before they threaten the survival of your shrub
or tree.
It’s important to realize that roots respond to pruning in much the same way as the crown: pruning
induces new growth. Roots that are pruned at transplant time, especially those that are excessively long
or misshapen, will respond by generating new, flexible roots that help them establish in the landscape. It
is vital that these new transplants are kept well-watered during this time.
A second problem with containerized materials can also be avoided during your root inspection. In
general, the media in the container is a soilless mix with a large proportion of organic matter and pumice.
If transplanted with the plant as part of the root ball, this material will inhibit root development outside
the planting hole. Furthermore, the porous texture of this planting media will often lose water more
rapidly than the surrounding native soil, resulting in increased water stress to your new transplant. It is
much better for root establishment to remove as much of the container material as possible before the
plant is installed. The best use for the discarded container mix is as a topdressing over the disturbed soil.
When covered with wood chips or another mulch that will reduce weed colonization, the container media
serves as a nice source of slow-release nutrients.