Hello, I’m Andrea Castillo and this is Seasonal, a newsletter that connects you to the Bay Area food system, one fruit and vegetable at a time. Seasonal comes out twice per month, and each post highlights the most interesting aspects of one seasonal fruit or vegetable grown and harvested around the Bay Area. Find me on Instagram at @seasonalbayarea or e-mail me at to share your feedback and suggestions, I’d love to hear from you. If you’d like to unsubscribe, click the gray unsubscribe link at the bottom of this post.

This week we nerd out on Santa Rosa plums (available June - August).

won’t you be my neighbor?

After writing about the mysterious world of eggplants, I was not sure what fruit or vegetable to geek out on next. I went on an urban hike with my husband and our dog for inspiration and explored some of the neighborhoods in South Berkeley. It was a perfect sunny day and we walked past and under some prolific apricot and plum trees. The hundreds of fruit on these trees challenged the structural integrity of each branch—nature’s engineering somehow allowed the branches to bend just enough to support the fruit without snapping and breaking. The abundance of fruit tempted me to snag one of the apricots or plums but it didn’t feel right to take without asking so I left them alone.

Halfway through the walk, we turned a corner and paused to read a sign: “Free Santa Rosa Plums! Take a Bag!” What a generous offer from a stranger, I thought. We kept walking past the house but the resident who was sitting on her porch called out to and urged us to take a bag. Their Santa Rosa plum tree was overwhelming them with too much fruit and they really didn’t want us walking away empty-handed. How could we turn down an offer on free, local, home-grown Santa Rosa plums? We grabbed the bag, thanked the friendly neighbor, and at that moment I knew exactly what to nerd out on for this post. 

Several ripe, fresh Santa Rosa plums, grown in a Berkeley backyard.

branching off

There are dozens of edible plum cultivars and they come from two main species: Eurasian (P. domestica) and Asian (P. salicina). Most of the Eurasian plums are usually dried or made into preserves, while the Asian plums are eaten fresh. The Santa Rosa plum is a cultivar within the Asian species and even though its historical origin is rooted in Japan, this stone fruit is so Bay Area. 

(Stone fruits, by the way, include plums, apricots, cherries, peaches, nectarines, and almonds, and get their name from the stone-hard shell that protects the seed at the center of the fruit. Stone fruits are also found in the most unusual places! Thanks to Harold McGee, I learned this crazy fruit factoid: each little juicy segment of a raspberry or blackberry is a complete stone fruit. 🤯 )


But let’s get back to the Bay Area-ness of the Santa Rosa plum. Without unexpected venture-capital funding, an insatiable entrepreneurial spirit, collaborative teamwork, open international trade, countless trials and errors, and abundant A/B testing, the Santa Rosa plum would not exist. Luther Burbank, a plant breeder and farmer from Massachusetts, was an avid fan of Charles Darwin and later in his life used selective plant breeding to create the Santa Rosa plum. Like many East Coasters in the mid-1800s, Burbank was itching to go to California and financed his trip with a potato: he developed a new kind of large, firm potato from a rare seed and sold the clones of his now-famous Russett Burbank potatoes—the most widely grown potato in the United States—for $150 bucks, enough to fund his trip out west. He already had a couple of brothers who lived in Santa Rosa so he settled in the Bay Area. Like so many of us non-native Californians who live here, Burbank became a transplant. He established a nursery and dedicated four decades of his life to conducting more than 100,000 plant experiments. It’s hard to imagine Burbank slept much: his prolific plant breeding included all kinds of vegetables and fruits, including tests on 30,000 new varieties of plums. 

international relations

Burbank’s thousands of plum experiments couldn’t have started without the brand new trade relations established between Japan and the United States in the late 1850s. Native wild plums were the only plums available in North America and native peoples harvested them for thousands of years. Even though native wild plums were hardy, they were also small, tart, and astringent with stones that clung vigorously to the flesh. After Europeans arrived in the late 17th century and began to take over the east coast of North America, they weren’t keen on the native plums all around them and imported the Eurasian plum species they already knew well, bringing them along to California as they ventured west in the early 1800s. But, the European plum cultivars did not travel well and it was difficult to eat them fresh.

As part of a quest to develop a new kind of plum, a Mr. Hough from Vacaville worked with the U.S. consul to import Japanese plums (P. salicina) to the United States in 1870 and John Kelsey, a horticulturist from Berkeley out of all places, used those plum seedlings to grow Japanese plum trees for the first time in North American soil in 1874. It’s entirely possible Kelsey grew those trees right here in the East Bay. After all, Kelsey lived north of Russell Street and east of College Avenue in Berkeley and he gifted his new plum trees to neighbors nearby. Kelsey’s Japanese plum trees were particularly adept at thriving in droughts and packed as many as six plums on a six-inch-long branch, two qualities that caught Burbank’s eye.

buddhist monks, christian missionaries, and pushy americans

But let’s rewind a handful of centuries before getting back to the plum imports that enabled Burbank’s life work. Japanese plums are not native to Japan. Japanese plums are Chinese and originate from the Yangtze River Basin in China. We do not know how the Chinese plum made its way over to Japan, but we do know it was introduced to Japan early on. It’s possible that a Buddhist monk brought Chinese plum trees to Japan as a gift to the Emperor more than 2000 years ago, a time when farmers from the Korean Peninsula immigrated to Japan and mixed with the native hunter-gatherers, creating a more agricultural society.

It seems that for 2000 years, the Japanese plum remained in Asia and did not venture out until Matthew Perry, a United States naval officer sent by President Millard Fillmore, showed up in Japan—uninvited—to strongly encourage diplomatic relationships in 1854. After a rocky start and diplomatic embarrassments for the United States, Japan reluctantly signed its first trade treaty with the United States in 1858. (Japan closed off to most of the Western world between the 1600s and 1800s because they feared foreign religious influence: they did not want Christian missionaries, banned Christianity, forbade Japanese from leaving, and did not allow Europeans to enter Japan—except for the Dutch.) A few years before the trade treaty, the United States admitted California as a free state so it was easy to establish direct trade routes with Japan, making it possible for the Japanese plum tree to make its first trans-Pacific journey to sunny California. 

infinite experiments

The timing was perfect for Burbank. He was eager to carry out plum experiments and after tasting and researching Kelsey’s Japanese plums in the mid-1870s, he ordered dozens of plum seedlings from Japan. To Burbank, Japanese plums had excellent qualities: they were rapid growers with early and abundant fruit and unusual adaptability to wide ranges of climate. Even though many of Burbank’s plum orders died on their way over, he was able to grow a few hardy and healthy trees from 12 little Japanese seedlings, including a plum with red flesh he named Satsuma (in honor of the province in Japan where it came from). In 1885, Burbank bought a farm in Sebastopol where, in his words, he “mated [the] immigrants from the Orient with European stock” in search of sweet, juicy, and abundant plums. He dedicated eight acres of land solely to his experiments, which, to the annoyance of scientists today, he sometimes failed to document, and did not stop hybridizing thousands of plums until he died in Santa Rosa in 1926.

It’s easy to understand why he experimented for so long. Plant breeding naturally requires time and Burbank patiently waited for each season to test hundreds of new plum varieties. In his notes, he wrote, “the fruit is not over when the plum is produced; the fruit must be tested under varying conditions and in successive seasons.” And for Burbank, seasonal testing was the easy part, only requiring patience and open-mindedness. The hard part was growing plums from seed and sorting through extensive variations to select the best qualities. Sometimes, Burbank would cross native plums with Japanese plums and then pollinate that new variety with another plum tree and wait years for this new creation to bear fruit. When the tree finally grew fruit, he’d realize he nailed every single desirable quality except for flavor so he would destroy the defective plum. He would then go back to the drawing board and try a new cross between plums that would yield every desirable quality and flavor (unfortunately, selecting desirable qualities in plants inspired Burbank to explore how to do the same with humans and he supported the eugenics movement in its early days—along with Alexander Graham Bell, Margaret Sanger, and President Teddy Roosevelt). In the plant world, Burbank’s patience and open-mindedness paid off. His exhaustive plant experiments yielded 113 plum and prune cultivars, among them his most famous plum cultivar, the Santa Rosa: introduced in 1906, it was a cross between the Satsuma (hence the Santa Rosa plum’s red flesh) and the apricot plum.

a special creation

We now know how P. salicina’s 2000-year adventure allowed Burbank to meticulously try, try, and try again to create new plum varieties, but what’s the big deal with the Santa Rosa plum? The Santa Rosa plum is not widely available throughout the United States—because it’s prone to pests, commercial growers have opted for more bacteria-resistant varieties that do not taste as great. However, stone fruit growers around the Bay Area continue to grow Santa Rosas (thank you!) and the best place to find them is at our local farmers market and stores. Bryce Loewen from Blossom Bluff Orchards in the San Joaquin Valley (southeast of Fresno) grows Santa Rosa plums among 16 other plum and plumcot varieties. He explains that “the Santa Rosa is special because of its balanced flavor (sweet interior, tart skin) and juicy texture as well as its history and pedigree.” 

It’s impossible to ignore the sweet fragrance Santa Rosa plums release as they ripen and they’re excellent raw, as a snack or dessert. The best way to store plums is to place them on your countertop and check them daily. When they feel a little soft to the touch and fill the room with their incredible aroma, they’re ready to eat or to go in the fridge. When ripe, their flesh will be sweet while the skin remains tart, a perfect combination for delectable baked goods. Unlike other plums, the Santa Rosa plum is juicy and does not get mushy when ripe. 

vive la France!

For me, baking was the perfect way to use all the Santa Rosas we picked up during our urban hike from the friendly Berkeley neighbor. If you can get your hands on a couple of pounds of Santa Rosa plums, I recommend transforming your kitchen into a temporary pâtisserie and baking your plums into a galette or a clafoutis. Jacques Pepin has a classic plum galette recipe and it’s hard to go wrong with the two sticks of butter he calls for. Feeling lucky I happened to have all the ingredients Ina Garten called for in her recipe, I also made a plum clafoutis for brunch last weekend (in my cast iron pan instead of in individual gratin dishes), and had a blissful meal. 

Heavenly Santa Rosa plum clafoutis: good for breakfast, brunch, or dessert.

uncovering elephant gems

Though the Santa Rosa plum’s fame is well-earned, there’s another Burbank gem hidden in the plum world that even Santa Rosa plum aficionados do not know about (Barney, if you’re reading this, that would be you). When I asked Bryce about other noteworthy plum varieties, he said the Elephant Heart plum has an even better flavor than the Santa Rosa, “and they are very aesthetically interesting as well with their grayish skin, blood-red flesh and heart shape. They are super special.”

Well, that sounds like the exact kind of plum Burbank dreamed of creating and spent countless hours refining. And this precious plum may have been one of the last plum varieties he worked on: Burbank died before he could release the Elephant Heart variety and a nursery he entrusted with his work introduced it in 1929, three years after his death. A surprising fact about Burbank’s life’s work is that he never raked in big profits from it. Even though his inventions and accomplishments rival those of top Silicon Valley entrepreneurs, he lacked one key protection most successful modern-day biotech entrepreneurs can count on: patents. Before 1930, plant breeders had few opportunities to profit from their inventions and while Burbank sold some of his trees to get by, he died near bankruptcy despite his innovations. I’m struck by how far motivation can take you: my desire to develop a deep connection with food motivates me to keep writing Seasonal, especially during overwhelming weeks when job applications go into black holes and the future feels particularly uncertain—and it’s only been four months! For Burbank, 40 years of non-stop mix n’ matching with plums and other plants did not ultimately result in a big payday, but he paid it forward with the delicious fruits of his labor.

Even though Elephant Heart plums are delicate and much more boutique than the Santa Rosa plum, fruit growers around the Bay Area like Blossom Bluff Orchards still grow them. It’s unlikely to encounter them during a random urban hike in Berkeley but Elephant Heart plums should be hitting farmers’ markets in a couple of weeks. Soon we will have the opportunity to taste the special flavor of the history, patience, and endless testing that went into the ultimate quest for supreme plums.

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Andrea Castillo is a food nerd who always wants to know the what’s, how’s, when’s, and why’s of the food she eats.