Phisherman wrote:

When/how should the azalea be moved to increase chances of
survival?

Because the roots grow near the surface, a bed prepared especially for
rhododendron and azaleas need not be more than 12 inches deep; deep
planting or too much mulch in the growing season keeps the roots from
getting the air they need. In fact, it is a good idea to set
rhododendron about 1 inch higher than they grew at the nursery.
Balled-and-burlaped plants may be transplanted in blossom but it is
better to transplant them early in spring in areas where their hardiness
is questionable, and in spring or fall if mild winter weather does not
damage the shallow-rooted plants. Fall transplanting makes a plant more
susceptible to frost heave in climates where freezing and thawing cycles
are common. All except leathery leaved rhododendron transplant best in
the spring.

When transplanting a large plant several steps should be followed.
First, it is best to stimulate a tight root ball by root pruning the
plants to be moved about a year before moving. This is accomplished by
cutting a circle around the plant stem with a shovel to cut off roots
that extend beyond this point. This radius is usually slightly smaller
than half way to the drip line. Second, it is best to move when the
plant is dormant and not stressed. This would be in the spring and fall
when the plant is still dormant but the soil is not frozen. Moving in
the fall before the ground freezes is preferable if you don't have a
problem with frost heaving. Sometimes winter freezing and thawing cycles
can actually lift a transplanted plant out of the ground where the roots
are then desiccated and the plant dies. For this reason, it is safer to
transplant in the spring after the ground thaws in climates where frost
heaving is a problem. Third, take precautions to preserve the integrity
of the root ball. Tie the ball together and support is so it doesn't
fall apart. Finally, pruning the top helps match the demands of the top
to the capability of the roots after they are stressed by the move.
People have been known to cut the top off wild rhododendron before
moving and the plants have come back with superior shape. This is
drastic and not recommended for a plant you don't want to risk loosing.
Rhododendron and azaleas have dormant buds beneath the bark which sprout
to form new growth after severe pruning, hence severe pruning which
removes 1/3 to 1/2 of leaf area is quite common when transplanting.

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