I live in central Etobicoke and would like to know which viburnum to plant with a Nannyberry, Viburnum lentago, in order for cross-pollination to occur. I have two burkwood viburnum presently in the garden.
Although the flowers of Viburnum lentago is perfect (i.e. possessing both male and female reproductive parts), they are self-infertile and require pollen from another genetically distinct plant of the same species in order to produce seed and set fruit. Therefore your existing Viburnum x burkwoodii would not aid in pollination; you need another nannyberry shrub. If you purchase nannyberry plants raised by seed, then you should be fine, since these plants will be genetically different. However, if the plants were produced asexually (e.g. via suckers, grafting, cuttings…), then there is a chance that the plants can be genetically identical. The only way to be certain is to know the grower, so shop from a reputable nursery or, even better, a specialized native plant nursery when you purchase your nannyberry shrubs.
We wish you the best of luck with your nannyberry shrubs.