I acquired this lovely UBC introduction some years ago. I have recently read of the suspicions by one esteemed author that this cultivar may be the same as 'Nanum Semperflorens' or 'Watanabei. Could somebody set the record straight? Thanks.
I have also heard that it is the same plant as Watanabei. It certainly has the same habit when they are grown side by side.
I'll also add that there is nothing "nanum" about 'Summer Snowflake' - grows to over 3m, unlike the description of 'Nanum Semperflorens' and 'Watanabe' from here: http://www.joycreek.com/529-030-1.htm
2002 Edition of HILLIER MANUAL OF TREES & SHRUBS has these two relevant entries: "'Nanum Semperflorens' ('Watanabe') A slow-growing form of dense habit with white flowers produced over a long period during summer and autumn. It was found as a seedling in the wild in Japan by Kenji Watanabe about 1956. Dwarf plants reaching 50cm and found in the wild at the foot of Mt Fuji in Japan have been described as f. watanabei (Honda) Hara." "'Summer Snowflake' A medium-sized shrub with tiered branches and lacecap-like flowerheads in May and through summer. Leaves red to purple in autumn. Similar to and possibly the same as 'Nanum Semperflorens'."