How to Prune Seemann's hydrangea?
Routine pruning is unnecessary; shorten overlong shoots to fit the available space. Prune after flowering has finished.

Seemann's hydrangea · Hydrangea seemannii
Grow in sun or shade, in a moist but well-drained soil enriched with well-rotted organic matter. Will only tolerate a few degrees of frost
Routine pruning is unnecessary; shorten overlong shoots to fit the available space. Prune after flowering has finished.