It was always the white one that I knew and grew in Connecticut, and grow here in New Jersey. My original plants came from John Osborne, a noted rock gardener in Westport CT. He got his original plants from Harold Epstein, a travel agent who lived in Larchmont, New York. He also had a marvelous garden. Harold (always spiffy in a sport coat and tie, conducted trips to Japan. and brought back plants. My P. obovata 'Alba' grew quite happily in woodland shade. The plants produced lots of viable seed, and I would just poke the seed around "mother", then in 3 or 4 years move seedling plants around. I also had P. japonica. One difference I noticed was that in the early stages (just before or when first pollinated) the green ovaries of P. japonica were taller / slimmer than those of P. obovata 'Alba', which were rather squat by comparison. I have several 'Alba' here in NJ, but cannot say they are doing as well as in CT. More compost is probably the answer, it's the answer to most of my gardening problems. Judy in NJ where nights are delightfully cool and days breezy and comfortable. Last Wednesday's storm (16 May) dumped 3/4 inch of rain in 20 minutes.