This agapanthus has proven to be hardy for decades, which can't be said for all of the newer hybrids, and we've tried a few.
We aren't certain when Ed Dunn purchased these plants, but they've been in the garden for at least thirty years. Completely deciduous, this selection doesn't have the deepest of blue flowers (which we really like), but reliability is definitely worth something.
As with so many plants that we like to use, some supplemental summer irrigation is important, if you want large, healthy clumps. And, be careful in siting them, as you don't want companion plants suffocating the crown, as agapanthus resent being crowded.