This amazing story was best told by Harry Randall in his terrific book Irises (Taplinger Publishing Co. Inc., NY, 1969 - Highly recommended!):
Amongst her early purchases Clara Rees had obtained Thais, a rosy-mauve diploid iris raised by Cayeux in France, with 24 chromosomes, narrow petals and drooping falls. Later on her sister, Ruth Rees, bought three other irises including Purissima, a tall, white tetraploid, for $18; and Clara thought, to quote her own words, that such extravagance proved that Ruth must have taken leave of her senses. However, Clara liked the colour of Thais and in due course she crossed it with the taller Purissima in the hope or getting the rosy-mauve colouring on to a tall stem and larger flower. The aim was an admirable one, but in the ordinary course of events any resultant seedlings would have been sterile triploids with a chromosome count of 36. There was a remote chance, however -- probably one in several thousand -- (a) that one of the pollen grains of Thais might have more than its usual quota of chromosomes, (b) that this grain might fertilize Purissima, and (c) that any seedlings might therefore be fertile tetraploids with 48 chromosomes.
Without knowing all this at the time, and with a boldness of which Sir Michael Foster would surely have approved, Clara Rees made her famous cross and succeeded in producing one solitary seed-pod. This pod, instead of containing, as expected, from 20 to 40 seeds, yielded only two, and one of these was so shriveled that it was promptly thrown away. The remaining seed was almost discarded because Clara Rees thought that there was no use bothering with a single one; but a spark of hope kindled the fire of compassion in the Rees household, the seed was saved and sown, and it ultimately proved of greater value than the Scriptural pearl of great price. If I were a parson I could preach a tremendous sermon on this historic incident!
In 1938, three years after pollination, the seedling gave its first flower -- not the rosy-mauve that had been hoped for, but a white slightly tinged with blue. One can imagine the delight and excitement of those who first saw the plant, winch had qualities not previously seen In a white iris -- broad, ruffled petals, clear hafts, several buds in each spathe, good branching and and excellent blue-green foliage. Nothing was done with the seedling in the first year of blooming except that it was dug up, split up, and the half-dozen resultant rhizomes replanted. Next year they all flowered and caused even more excitement. The two sisters decided that something ought to be done to enable other people to see the new arrival, and Clara afterwards wrote: 'Ruth felt that the bloom deserved the scrutiny of an experienced iris breeder, so she cut two of the individual blooms and traveled to Berkeley by street-car, train, ferry and taxi and showed them to Carl Salbach who at once asked, "Young lady, where did you get these?" Ruth told him that they had come from a seedling raised in the back yard of our home in San Jose.' Salbach quickly visited that back yard and bought the entire stock of Snow Flurry, which had then increased to 17 rhizomes, but he allowed the raiser to keep one rhizome.
Years later Ruth Rees wrote:
The next chapter of the 'Snow Flurry' story belongs to Orville Fay who, when he read the description in Salbach's catalogue, realized that if the parentage, Purissima X Thais, was true it would be a great breeder. He therefore asked his friend, Junius Fishburne of Virginia. who was attending an Iris Convention in California, to look at the plant and answer certain questions -- Were the spathes papery? Were there many buds in each socket? Was the foliage vigorous and blue-green? and so on. As the answers were all satisfactory Orville bought it, and we all know what he has done with it.
'Snow Flurry' went on to become perhaps the most celebrated parent in iris history. Thousands of iris varieties have these particular genes somewhere in their ancestry. It changed the course of iris breeding for generations and has left a legacy that others can only aspire to. And today, 'Snow Flurry' is still a fantastic garden iris and a fitting legacy to the ladies who recognized its potential.
[Update: photos previously posted with this article were mis-identified and have been removed. Images were of the variety 'Purissima'. - Mike]