Yellow flowering Cassia Tree with frost/freeze damage. This picture was taken January 14, 2010 about 1 week after a hard freeze and several nights of frost.  This young tree was damaged extensively in the previous year from a frost/freeze event but had recovered to about the same size at the time of this picture.  Most of the branches smaller than 1-2" in diameter will die.  Wait until March to determine where pruning needs to be done.  After pruning, way too many new shoots will sprout and grow.  When the new shoots begin to develop to about 12" long you will need to pick dominant branches and prune off the many excess branches to develop a nice canopy.