So bottom line 1 viburnum doesn't influence another's ability to flower, ONLY the berries, correct? Correct - flowering is affected by sun exposure and plant maturity. Viburnum x rhytidophylloides 'Allegheny' is the cultivar itself (as denoted by the single quotes around the name). The official name for Mohican is Viburnum lantana 'Mohican'. The key for cross pollination is overlapping bloom times - without that, it won't happen. And for some viburnums, they are not compatible even with overlapping blooms. Here is a link that might be useful: You might enjoy this thread

My 'Blue Muffin' has a bloom time that coincides with my Viburnum acerifolium and the two pollinate each other and both set fruit. I do think that when different viburnums flower in an individual yard can differ from how it happens elsewhere ... you really just have to strive for something that is POSSIBLE and then see what happens. But if two people agree that Chicago Lustre is a later blooming cultivar for them, that would not be the first one I'd try. We don't know where the original poster lives, and that certainly can affect which cultivars are available and how they perform. For example, I don't think that some cultivars (like Chicago Lustre and Red Feathers) are sold in my area (Georgia) nor are they known for thriving in our heat. Here is a link that might be useful: Here's an old thread on V. dentatum bloom sequence

Yes, there it is on Landscape Design. Steve, I hope you got the answer you needed after posting it in all those places :) Good luck, viburnum is certainly a wonderful group of shrubs. That is a great old classic thread that Brent linked there and worth linking again here for folks that don't go over there. Here is a link that might be useful: Original viburnum dentatum and friends thread

Fifty feet should be fine.