Proper Methods for Trimming Viburnums

When to Trim

• Viburnum plants that produce their flowers prior to June 15 are said to bloom on old wood, while those flowering after June 15 bloom on new wood. The appropriate time for pruning viburnums is immediately after flowering in late spring or early summer.

What to Trim

• When pruning viburnums, trim about one-third of the most mature branches of established plants. Prune the plants regularly but lightly to maintain vigorous growth. Certain species such as Viburnum plicatum var. tomentosum produce rapidly-growing, non-flowering vertical shoots. Remove these entirely, as they spoil the natural horizontal shape.

What Not to Trim

• If you prune viburnums very extensively, it reduces their flower production. The fruiting viburnums have reduced fruit if heavily trimmed. Avoid trimming the plants into specific shapes, as this ruins their natural form.