I tried a simple Google search using the terms 'Agapanthus' and 'Hardy' and found that High Country Gardens, of Santa Fe, New Mexico has a blue selection that they claim may be hardy to USDA 5b, and hardy from USDA 6-9. http://highcountrygardens.com/catalog/product/… They claim USDA 5 hardiness for a white selection which was identified as a chance seedling in Michigan http://highcountrygardens.com/catalog/product/… Jonathan Knisely New Haven, CT USDA 6a