I grew up in the pre-silicon Santa Clara Valley, where the California prune industry began. In 1856 a Frenchman named Louis Pellier failed at gold mining and started a nursery in Santa Clara. He introduced prunes to the United States by grafting a variety of French prune plum to the root stock of the native Santa Clara Valley wild plum. The result was a plum that would dry without fermenting around the pit.
The poor prune in this country has long been something of a joke, and subject to clever advertisements: "Today the pits, tomorrow the wrinkles!" intoned a stentorian baritone voice in an early television ad. A later ad labeled it "The funny fruit." Now prunes tend to be labeled "Dried Plums" to the amusement of prune growers. All prunes are plums, but not all plums are prunes.
The 1933 edition of the Sunset All-Western Cookbook takes up the issue, quoting Jeannette Cramer of Sunset Magazine:
When is a plum a prune, if ever? That question has been debated for a good many years. The impression seems to exist in some places that a plum becomes a prune after it has been cured, somewhat after the fashion of a tadpole which becomes a frog after it has passed through a series of finishing processes, and even the lexicographer agrees in that.
I, however, prefer to stand on the side of the practical fruit man who gives the prune credit for separate existence even while on the tree. We go so far as to refer to prune trees and prune blossoms, than which there is no more delightful snowy sight in all the spring-time display. A drive through a prune-growing region on the annual blossom day is one of the favorite joys of all who dwell in or near prune-growing communities.
As Dad once put it with a grin and a wink, "prunes is prunes."The prune orchard was the focus of our lives when I was growing up, and it gave us our living. In the spring came the buds all over the trees—then the blossoms, sweet and profuse, perfuming all of Santa Clara Valley. The blossoms set and, barring killing frosts, turned into little green prunelets.
As summer went on, the prunes turned deep purple. The fruit became fat and heavy, and Dad put props under the drooping tree limbs to support them and keep them from breaking. The early prunes began to fall from the trees. Their smooth dusky skins were thick and sour, their pulp golden and sweet.
Then the harvest! Out we went with our tin buckets and began to pick prunes. On our knees around each tree we went, picking up the purple fruits and chucking them into our buckets as fast as we could. Fill a bucket, dump it into a box, pick some more.
Never did we say we were “picking plums” as we scrabbled around the hot dusty orchard on our knees, picking up the deep purple fruits.
We were Picking Prunes.

