Answer: Japanese snowball (Viburnum plicatum) produces sterile flowers and should bloom without the company of another Viburnum. (Viburnum tomentosum, the Doublefile Viburnum, produces similar flowers, which develop fruits at the end of the summer. These plants benefit from cross-pollination.) Your snowball might be too young to flower, or it isn't getting enough direct sunshine (8-10 hours per day). Other reasons for non-blooming include improper pruning (prune in early summer to provide ample time for the plant to generate flowering stems for the following spring's flower display), or too much fertilizer - which results in lots of vegetative growth at the expense of flowering. Hope the above information helps you determine the cause of non-flowering in your Japanese snowball!
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