Answer: This plant (Callicarpa) blooms on new wood of the season, so you need to promote new growth and also be careful about any pruning -- trimming off this year's blooms will trim off berries.
This plant is hardy into zone five, but you might want to protect it from excess wind as well as provide it with a heavy mulch each winter. If you fertilize, use a complete fertilizer such as 10-10-10 and avoid oversupplying it with nitrogen as this may contribute to excess foliage growth at the expense of blooms.
Many gardeners will treat this as a cutback shrub, trimming it back quite hard each spring, even as short as a foot. Pruning would be done in early spring to remove any winterkilled branches, as well as to promote new growth. Do not prune later in the season.
Finally, it also seems that berry production is enhanced when two or more bushes are planted. I hope this helps you trouble shoot!
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