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. Each post highlights the most interesting aspects of one seasonal fruit or vegetable grown and harvested around the Bay Area. Seasonal is a public good, and all past and future posts are free to read, but if you want to support my quest to deepen our connection to food and contribute to building a stronger food community, please consider becoming a paid subscriber for $5/month. Find me on Instagram at @seasonalbayarea or e-mail me at seasonal@substack.com to share your feedback and suggestions, I’d love to hear from you. If you’d like to unsubscribe, click the link at the bottom of this post.

This week we nerd out on watermelons (peak season May to October).

All living beings on Earth constantly search for water—tree roots grow into cracked or leaky underground pipes to access the water they carry, camels can go a full week without drinking thanks to the unique water-storage capacity of their oval-shaped red blood cells, and humans have used technology to produce several gallons of water per day out of thin air. In fact, humans have been designing tools to access, store, and harness water for millennia. Romans built their famous aqueducts 2000 years ago. Four thousand years back, the elite Minoans in Crete already enjoyed the luxury of flushing toilets.

edible oasis

One thousand years before the first flushing toilet, attentive and dedicated farmers in the dry areas west of the White Nile in present-day Sudan figured out how to grow water from the ground—water that was delicious and made it through long, slow desert journeys without spoiling. How did they do it? The watermelon.

For decades, puzzled researchers could not figure out where watermelon originated. In the summer of 2021—just now!—with advances in genome mapping, botanists and plant scientists finally pinned down Sudan as the most likely birthplace, tying watermelon ancestral roots to the white, pale, Sudanese Kordofan melon. What was the clue? Bitterness—or lack thereof. All wild melons in the watermelon genus—Citrullus—in west, south, and north Africa are bitter. Yet, the Kordofan melon has an unexpected sweetness to it: its genes do not express bitterness and yield sweet fruit instead. The first trait that hooked people to selectively grow Kordofan melons was its unique sweetness, a taste we are hard-wired to crave.

nature’s souped-up Nalgene

Watermelon, nature’s version of a Nalgene, LifeStraw, and Emergen-C all combined in one, evolved to be the perfect desert fruit (note: botanically watermelons, squashes, and cucumbers are all in the same family and are fruit, but culturally we use most of them as vegetables except for the watermelon). Not only was it durable and transportable like a Nalgene, it also contained clean water inside when it was needed most (during dry seasons when rain was not available as a source of potable water), and the edible flesh was packed with powerful antioxidants and vitamins A and C. A plant that grows in a difficult, dry environment, quenches your thirst, boosts eye health, strengthens immune systems, and is slow to spoil is a pretty sweet gift from nature.   

One more awesome watermelon quality is its color. Watermelon is refreshing not just because it’s 92% water, but also because it is red inside. Psychologically, we tend to associate red color with something irresistibly refreshing!

In 1924, a National Geographic Magazine writer chronicled his adventures in Sudan from 1916 to 1920, in which watermelons played a key role. He enjoyed watermelon tea the locals made—after punching the fruit open and squeezing the flesh to press the juice out—and, in brutal 110-120F heat, endured a six-week journey on which watermelons were his sole source of water. The writer, Major Edward Keith-Roach, complained about being unable to shave during that trip but couldn’t praise watermelons enough for saving his life and making the trek possible.

slow exit

Watermelons stayed in Africa for a while and it would take thousands of years for the refreshing plant to reach California. In ancient Egypt, pharaohs enjoyed the red, fleshy fruit: watermelon paintings adorned 4,000-year-old Egyptian tombs, including King Tut’s. What better treat than a durable 10-pound fruit holding a gallon of water inside? Doubling as food and drink, watermelons were a must for the underworld journey. Watermelons arrived in India and China in the 7th and 10th centuries respectively and the Moors introduced them to western Europe in the 13th century. By 1576 Spanish colonialists had planted watermelons in Florida. From there, they spread to the American southwest in 1598 where the indigenous people already living there grew fond of the new crop. Plus, watermelon was a long-lost cousin of the squashes indigenous people were used to growing (watermelons and squashes are both members of the Cucurbitaceae family) and, as a bonus, watermelons did not mind the long, hot, southwest summers.  

water, water everywhere

When watermelons showed up in California, the landscape was lush with overflowing lakes and rivers. A mere 140 years ago, a shallow, 790-square-mile lake lay smack-dab in the middle of the San Joaquin Valley, stretching across Tulare and Kings Counties. Tulare Lake was the largest lake in the United States West of the Mississippi. It was home to abundant fish including salmon, a pit-stop for birds, and a source of water for the surrounding wetlands that sustained Yokut tribes for centuries.

In the 1850s, people flocked to California in a mad quest for riches, and these Gold Rushers needed food. Limited supplies shot food prices to the moon and the extreme profits in farming attracted entrepreneurs. Watermelons were easy to grow and very profitable: an individual watermelon farmer could net up to $178k in a single year from their crop. In 1870, two partners, Eddlemon and Northrop, took a bet that Lodi—between Sacramento and Stockton—would be a good place to give watermelons a try. There was no irrigation available at the time so it wasn’t the most obvious choice. But what they noticed that others didn’t was that water lay a few feet below the surface. Luckily, watermelon roots can grow deep and do not depend on surface water from irrigation. With enough water available a few inches underground from snowmelt and spring rains, Lodi watermelons flourished. At one point, Lodi was dubbed the Watermelon Capital of the World. Unfortunately, Lodi’s groundwater dried up by 1890, and the watermelon crops withered away.

water, water… nowhere

Lodi in 1890 was a microcosm of the overall water situation in California. By the end of the 19th century, farmers, ranchers, miners, business people, and engineers had all undertaken one of the largest agricultural infrastructure efforts in the world, permanently transforming entire ecosystems throughout the state. Without irrigation, it would have been difficult—if not impossible—for farming and ranching to take off. So, California newcomers built canals and dams to bring in water from rivers and lakes to farms throughout the Central Valley where agriculture exploded.

With the new dams and canals diverting water into private farmland to grow cotton, alfalfa, and raise cattle, the physical landscape transformed in a few short years. Tulare Lake, for example, was choked off and dried by 1898, leaving behind a cracked mud pit. Since then, continuous water diversion, groundwater pumping, and droughts have dried up larger swaths of thirsty Golden State land.

Where Tulare Lake once existed is now one of the top watermelon-producing areas in California. The United States grows about 3.9 billion pounds of watermelon each year: Florida accounts for the most with 907 million pounds and California supplies 494 million pounds. Recently, domestic watermelon production has been declining even though watermelon demand grows and grows. In California, the land is parched and it is increasingly difficult to keep up with current levels of production. Water pumping continues without limits, reducing groundwater to the point where some California towns simply run out of it. Drought has forced the state to impose restrictions and farmers to make difficult decisions. Crops are suffering. To make it worse, the extreme heat we’re experiencing from climate change stresses plants even more. 

California-grown pink watermelon getting ready to quench a thirsty writer.

just because we can, doesn’t mean we should

In general, we’ve designed our food system to reward high yields of good-looking crops—the more the merrier. High yields would be impossible without lots of water but our insatiable thirst for it is catching up to us, and business as usual for agriculture will be hard to sustain.

Watermelons need water to grow an abundance of fruit but they also don’t need that much water to thrive. Watermelons can withstand heat and water stress well—as their wild ancestor did for so long in arid Sudan. Bolstered by drought-tolerant genes, watermelon is a crop resilient to climate change. Drought-resistant varieties have thick leaves and a deep root system, helping the plant find water stashed away deep below the surface—perfect for drought-stricken California. But not all watermelons are drought-resistant and over the years, some have been optimized for irrigated fields where water stays closer to the surface. Choosing and developing drought-tolerant over irrigation-loving varieties would help both humans and watermelons adapt to the stressful environmental conditions in California. Farmers in areas with extreme drought in China and Kenya, for example, have already switched to drought-tolerant watermelons and are co-existing with drastic changes in their climate.  

What else can we do? We could start by emulating what the Lodi growers did back in 1870: dry farm watermelons. Dry farming is an ancient farming technique that does not require irrigation, relying instead on the rain or snowmelt from mountains that becomes groundwater, and only recently went out of fashion. The Egyptians who loved watermelon so much in 2,500 BC practiced it, and the Gold Rushers who first started coming to California in 1849 also dry farmed. Today, less than one percent of farms practice dry farming: it’s a difficult switch and profits generally pale in comparison to what you could net with irrigated crops. Dry farming can work with the right crops though. Watermelons are great candidates for dry farming—along with tomatoes, olives, grapes, apricots, and garbanzos to name a few. If we can figure out how to expand dry farming, we can start curbing an over-reliance on irrigation and adapting to the realities of the drier, more extreme landscape we’ve created.

With longer drought cycles and climate change challenges, California may not be able to keep growing half a billion pounds of watermelon every year. Without an abundance of water, watermelon yields will drop. Farmers with watermelon crops adjacent to water canals in the San Joaquin Valley have had no choice but to leave a third of their land fallow. For consumers, there may not be as many watermelons to choose from and retail prices for California-grown watermelons may go up as cheaper imports from Mexico arrive. On the bright side, though watermelon crops would yield less without irrigation, the results would be tastier. Their sweet taste would intensify, similar to the famous burst of flavor a California dry-farmed Early Girl tomato offers.

By supporting farmers who minimize water use as they grow watermelons, we’d also be pitching in to support a future where water remains accessible in spite of the challenges ahead. Watermelons found ways to survive in dry conditions and sustain thirsty humans and animals around them at the same time. As humans, we need to find ways to tap into our primal need for water responsibly, ensuring the collective wellness of all living beings while replenishing the thirsty land beneath our feet.  

Liked watermelons? Nerd out on tomatoes, pears, or brussels sprouts next.

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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.