To my understanding - viburnum cross pollination is a bit tricky - those species are not closely related enough to trilobum to effectively provide cross pollination/fruit set. You need another clone (different cultivar or a seedling grown plant) of trilobum or V. opulus or sargentii.

It seems to be believed you can't even count on any random member of the same viburnum species to be fully cross compatible, same as with blueberries and avocado trees - hence recommendations to plant several clones of the same viburnum species together.

I think the concern there is that if you are working with cultivars, each individual of a given cultivar has no genetic variation to the next individual. If you were planting species arrowwood viburnums, each plant would have the ability to pollinate any other individual plant. It is when planting named varieties of this plant that one must take pains to plant a "complimentary" cultivar, one flowering at the same time.

Interesting. We do have some 'Wentworth' Trilobums already, more than one. Last summer the nursery also had some unnamed 'American Highbush Cranberries' too. I wonder if they would be genetically similar but different enough to be pollinators.

I think so, Xty. We used to have a top-flight Viburnum expert hang out here but he doesn't frequent this board these days. I'm sure he'd know. But if 'Wentworth' is a trilobum cultivar, and if what you are saying is that these straight-species plants are viburnum trilobum, then yes, they will do the trick. Keep in mind, in normal, non-cloned wild populations, each member of a group within a species is genetically different from every other member, so all will pollinate all others. It's just when we deal with cultivars, which are clones, that we get into this mess. And for the record, I have seen large plantings of a single arrowwood viburnum cultivar fruit like mad. so there's still some unknown here.

Some viburnum cultivars are self fruitful.

I planted 1g wentworths with redwing for x-pollination last fall along a fenceline. Both are just now leafing out. Yes there's a height difference but I only spaced them 6' apart so hopefully it's not a big deal down the line.

i also planted (along the same hedgerow) arrowwoods "Chicago lustre" x-pollinating "northern burgundy". 2g plants also starting to leaf out.

im years away from a flowering privacy hedge but this particular area is on a 5-year garden plan.

Matt, that is kind of my plan too! Long hedge along a fence for privacy, but I am hoping for somewhat of a consistent look. How tall do those varieties of Arrowwood get?

My understanding is 10-12' tall, not sure how long that takes. 6-8' will do the trick at my house to block the view.