Answer: Bumald spirea blooms on new growth of the season, so any pruning would be done in very early spring when it may be trimmed lightly to keep it looking tidy. After the first flush of blooms you may also tip it lightly to encourage a second flush of blooms. Nost of the Japanese spireas would be treated essantially the same way. In general you would not routinely cut any of these back to the ground at any season.
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