When is the best time to prune a broom shrub?

After the bloom is the best time to prune a broom shrub.

Specifically, the shrub blooms from April to June. Flowering is followed by ample seed production. A regular pruning schedule may be instituted any time between August and October. The earlier time will control seed production while encouraging leafy regrowth. The later time will control both.

But pruning for damaged, dangerous, dead, diseased, dying parts -- the pruning rule of the d's -- can be done at any time throughout the year. As is the case of regular pruning, it never should be done after a rain event or to wet wood, both of which tend to encourage tree diseases.