I am going to guess its because you recently put the plant in. Another viburnum isn't going to increase the flowers, it will help it produce berries. Wait a couple of years for the flowers. How big is your plant? There was a great thread on the shrub forum about this subject - which viburnum pollinates others. They have a few collectors over there that know a lot.

But in any case, another variety of V. plicatum should work well like Shasta. It can't be another Mariesii. Also, other types of viburnum that flower together might work as well. That is where the shrub forum will help you.

I guess my Maresii is about 5-6' tall. It's kind of twiggy so I am going to try pruning it in hopes of getting better leaf out.

I also created another post to find out where I can buy Viburnum plicatum tomentosum 'Newport' (Newzam) locally. It's a doublefile but only grown about 3'x3' -- perfect because I can't accomodate a 12' viburnum.

Ask a few people who are growing this because none of my compact viburnums have been as small as claimed so far.

Ah well, in any event, it's got to be smaller than the 12' variety.

I have the most beautiful viburnum, Mariesii.It's about 8 years old now and it has dinner plate size flowers every spring. I've never pruned it, so it is about 8' wide by 8' high. I hammer in a plant spike once a year for flowering trees and I scratch in some triple super phosphate, in the spring. that's it, and it pays me back with the most outstanding display every year, it's placed front and center in my front border and folks walking the neighborhood always stop and admire it and ask questions about it. I take some of the branches that are touching the ground and pin them down and cover them with soil and in no time at all I have new starts, which I cut from the main shrub and let them grow for a year and then I dig them up and give them as gifts to those admiring neighbors.