How to Prune king rhododendron?
Usually little pruning is needed. Lightly shape if necessary, removing dead, damaged or diseased shoots. Prune after flowering.

king rhododendron · Rhododendron rex
Grow in moist but well-drained, leafy, humus-rich acid soil in part shade with shelter; see rhododendron cultivation
Usually little pruning is needed. Lightly shape if necessary, removing dead, damaged or diseased shoots. Prune after flowering.