Shrubs generally flower based on sufficient age and sun exposure. Fertilization is generally not the issue, but you are welcome to have your soil tested to see if there is a deficiency that should be amended.

Is the viburnum getting enough sun during the summer months (after mature trees have leafed out around it)? How old is the viburnum, did it used to flower better?

Agreed that lack of fert is not the issue. As to what the issue could be, more info needed.

Dan

i drive by 100 year old abandoned homestead out here in the country ...

and the shrubs ARE HUGE...

never fed.. never watered.. ignored.. unloved..

and just enjoying life to the max ....

in summation.. shrubs do NOT need fertilizer ...

ken

The viburnum is about 7-8 years old. It gets sunshine from sun up in the morning till about 7:30 PM. It previously flowered but never alot. I will check the soil. The Ninebark shrub is only a year old and it gets more sunshine than the viburnum. Thanks for your help