June 2013 issue of the Cornell Flower Bulb Research Program Research Newsletter:
In 2002, we received some plants of Agapanthus ‘Sea Foam’, a small flowered, white cultivar. We planted it into our Cornell University perennial trials in Ithaca, NY. Until the recent revision of the USDA cold hardiness zone map, Cornell has been in the cold end of zone 5 (zone 5a, with average annual extreme minimum temperature of -20 to -15F or -29 to -26C). The new map now places Cornell in the warm end of zone 5 (zone 5b, with average annual extreme minimum temperature of -15 to -10F, or -26 to -23C). Still pretty cold if you ask me! The ‘Sea Foam’ planting
has flourished for 10 years, and has proven itself to be fully winter hardy.
Read the whole article. Starts on page 2.