Newly planted chokeberry's leaves turning, dropping
Last weekend I purchased and planted a red chokeberry (aronia arbutifolia 'Brilliantissima'). Two days ago, I noticed that almost half the leaves had turned a reddish yellow (from pictures I've seen, this would appear to be the fall coloration). The plant wasn't droopy or unhealthy looking. Today, many of those leaves have dropped, and more appear to have changed color. Has anyone else experienced this after planting this or another shrub, and should I be concerned?
I watered the shrub well when I planted it, and again several days later (after I noticed the change in coloration). It was not rootbound when I removed it from its pot for planting; the roots looked healthy and vigorous.
Could this be a normal reaction to the stress of having the roots disturbed during the planting process?