White Blackberries. What the F......K

Luther Burbank: His Methods and Discoveries (1914)

The white blackberry is an unusual white variety of blackberry developed by plant breeder Luther Burbank, also known as the iceberg white blackberry or snowbank berry, probably originating as a pun on the name "Burbank". Burbank tried out 65,000 unsuccessful crossbreeds[1] at his facility in Santa Rosa, California, before enjoying success in 1894.

Mr. Burbank learned that a wild blackberry of New Jersey, is lighter in color than any other blackberry, had been introduced as a garden novelty under the name "Crystal White." Although lighter than any other blackberry, it was of a muddy brown color. and the berries were small and of poor flavor. This wild berry, however, was the first step in the production of Mr. Burbank's perfected white blackberry.

A fine flavored, well fixed race of blackberries is the Lawton,  If the pollen of the wild white berry had been applied to the pistil of the Lawton berry little variation would have been expected, the latter being so prepotent. But, by applying pollen from the Lawton berry to the flower of the so-called "Crystal White," Mr. Burbank produced variations which retained the lightness of color of the wild parent and combined the size, flavor and other good qualities of the well fixed Lawton.

From among many crosses between the Lawton and the poor "Crystal White," a berry very much improved in size was secured, and the form, texture and flavor were brought up to the point, almost, of the good Lawton parent, while the color, though still far from white, was much lighter than even that of the wild "Crystal White."

Eventually, repeated selection and regeneration, a  true white blackberry is produced.The success of Mr. Burbank's production may be judged by the firm, luscious, pure white fruit as shown below. The white blackberry is now a thoroughly fixed race coming true from the seed — a fruit which, if found in the state of nature, would unhesitatingly be pronounced a distinct species. It is whiter than the whitest blackberry man ever saw before and compares in size and lusciousness with its paternal ancestor, the Lawton.