All of the honeyberries are hardy (to zone 2, I believe!), and so the only requirement I know of is to get 2 or more having overlapping bloom times so they can pollinate each other. In the case of this species, the bloom times I have identified overlap a bit already, so things marked 'midseason' (for instance) might also be compatible with both early-mid and mid-late groups. I think you could get up to 2 months of fruiting by planting a succession of bloom times.
