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 mandarins (October-March).

season finale

The most important thing to know about mandarins right now is this: mandarin season is nearing its end! We get to enjoy sweet and tangy mandarins for the rest of March and then it’s over until October. As of two days ago, the Berkeley farmers market, Market Hall in Rockridge, and Berkeley Bowl still had them. Don’t be shy about taking a break to run and grab some, this newsletter will still be here when you get back. Peel and eat raw, save the peels to fight garden pests, bake mandarin scones, or make yourself a mandarin glazed salmon for dinner. Even though the season is ending here in the Bay, mandarins still taste incredible and there are so many different varietals to try! 

a wild tasting

Even though it’s the end of mandarin season, I was able to hunt down seven different varietals. To optimize for taste, the mandarins sat on the counter at room temperature (never put them in the fridge). The next day they were ready for a home mandarin tasting. Each mandarin was heavy for its size—a good sign that there’s juicy goodness inside—and each offered unique tastes and aromas. The seven varietals for this tasting were:

  1. Murcott (organic)

  2. Tango (both organic and non-organic)

  3. Gold Nugget (both organic, and non-organic)

  4. Page (non-organic)

  5. Pixie (organic)

  6. Shiranui Dekopon (non-organic)

  7. TDE (organic)

The tasting started with the Murcott mandarin. When I asked Jake from Sunrise Farms at the Temescal farmers market about Murcotts, he said, “Have you ever heard of Cuties or Halos? It’s the same shit!” Jake explained that Cutie or Halo isn’t a variety of mandarin. Those are just the brand names given by Sun Pacific and Paramount Citrus (respectively), the companies that sell those mesh bags of mandarins or clementines. 

But I digress. Back at the tasting, the Murcott, Tango, and Pixie delivered the familiar taste of a sweet and tangy mandarin. The organic Gold Nugget was nothing but sweet and unfortunately the non-organic Gold Nugget and Page both had off tastes.

The non-organic Shiranui Dekopon was a hell of a surprise: it was a savory mandarin that tasted like apricots and had segments the size of a pinkie finger. Apparently, the Shiranui Dekopon is an exciting fruit that’s prized by many. When this Japanese varietal finally arrived in California and was successfully grown about nine years ago, it was a big deal and the LA Times wrote a whole article about this important moment.

As fun as the Shiranui was, the most exciting of all the mandarins by far was the TDE: a Temple Dancy Encore cross. This mandarin was on the verge of bursting, its juice sacs barely contained by the translucent wall that separates each segment. To my delight, the TDE tasted like pineapple! If you happen to find one around this time of year, grab it: the TDE mandarin is a complex little blend of tastes, all packaged in a citrusy hacky sack of tropical goodness. 

Sweet, tangy, savory, acidic, apricotty, and pineappley, all of this variety came from farms around Fresno to the Bay Area. But there was one common denominator between all the mandarins that drove me a little crazy. All the mandarins were orange on the outside and none were green. I wanted green.

A sea of orange with no green peel in sight. Top: Shiranui Dekopon. Bottom left: Murcott. Bottom right: TDE.

a green enigma 

Why would I be searching for green mandarins, you may ask? Well, having grown up in Colombia, most of the mandarins we juiced and ate when I was a kid had a thick green peel that protected the precious juicy segments inside. I distinctly remember color had no impact on taste. As a teenager, after moving 2,500 miles north to New England, I remember noticing how bland these tiny orange “Cuties” tasted. I acclimated to that blandness and orangeness. Until now.

All the fiery orange mandarin displays at the farmer’s market, Market Hall, and Berkeley Bowl prompted so many questions. Where did the green ones go? Are they different fruits? Was I misremembering the green mandarins of my childhood?

The easiest place to start was fact checking my memory. I called my father who grows a couple of mandarin trees in a tropical climate, and he confirmed that yes, our family often ate green mandarins, and yes, the ripe mandarins on his tree are still indeed green. Oh, but, by the way, they turn a little orange when it happens to be a bit cooler at night. Oh, really? Well, say no more because this is a big clue to the color mystery. There’s a reason his mandarins were turning orange! 

cold yields orange

Temperature is one of the keys to the whole color conundrum. Mandarin peels need cool nights to transform from green to orange. They have chlorophyll, a green pigment that give them their green color, and carotenoids, an orange pigment. So long as it’s warm out, chlorophyll will dominate and the peel will remain green. When temperatures begin to dip and are cool for long enough, the chlorophyll begins to degrade and carotenoids are able to take over, resulting in an orange peel.

But why would cold temperatures trigger such a radical color transformation? I started reading academic papers and calling plant scientists—reminiscent of the radish research hole from a few weeks ago. Dr. Ashraf El-kereamy from UC Riverside patiently assured me that we simply do not know the mechanics of how temperature triggers this color changing process. But we do know that temperature is the trigger. The reason green mandarins were so ubiquitous where I grew up is because it just didn’t get cold enough. That’s why they rarely turned orange! Around the Bay Area, nights are generally cool enough to trigger the green to orange color transformation, so our local mandarins end up orange. 

don’t judge a mandarin by its cover

As John McPhee elegantly explains in his book Oranges (which also applies to mandarins):

The color of an orange has no absolute correlation with the maturity of the flesh and juice inside. An orange can be as sweet and ripe as it will ever be and still glisten like an emerald in the tree. Cold—coolness, rather—is what makes an orange orange. In some parts of the world, the weather never gets cold enough to change the color; in Thailand, for example, an orange is a green fruit, and traveling Thais often blink with wonder at the sight of oranges the color of flame.

Yes! Exactly! Apparently McPhee has known that the color of a mandarin does not impact the taste since he published Oranges in1966.

gassing for orange

There’s a final twist in the story of mandarin color. Farmers who grow citrus in warmer climates harvest green, unwanted fruit. To solve the problem, they use synthetic ethylene gas to shoo away the green. During this process, known as gassing or degreening, citrus sits in chambers where synthetic ethylene gas circulates for a few days to destroy the chlorophyll in the peel and force it to become orange (or yellow in the case of lemons). While ethylene gas is not harmful to our health, manufacturing it from petroleum or natural gas is done in a not-so-environmentally friendly, energy-intensive way. Surprisingly, the USDA National Organic Program and California Certified Organic Farmers allow the use of synthetic ethylene gas to degreen ripe organic citrus.

What’s crazy is that gassing mandarins and oranges is done for purely cosmetic reasons. Synthetic ethylene does not ripen these fruits after they’re harvested. The gas merely changes the appearance of an already ripe gem, dressing it up for the produce aisle. We sure go to extremes sometimes just for looks!

All of that said, nature almost always takes care of mandarin cosmetics in Northern California, and luckily our farmers rarely resort to gassing mandarins. Glenn Wright, Extension Horticulturist for the School of Plant Sciences at the University of Arizona, explained that ethylene gas applications yield different results depending on the type of citrus. For mandarins, ethylene gas is too harsh and softens the peel. Mandarins gassed with ethylene do not transport very well and can damage easily. And, as the staff at the Full Belly Farm farmer’s market stand confirmed, temperatures around Northern California usually get cool enough to turn everything orange. If anything, extreme frost is the real danger, as it can kill the whole mandarin crop. 

it’s not easy being green

Still, green mandarins do happen and can sometimes make up about 5-10% of the entire mandarin crop for farmers in parts of Fresno County. For example, sustained warmer nights have yielded green mandarins for CJ and his family at their Fruit World farms. However, grocers do not want to buy ripe green mandarins because consumers do not know they are just as good. Instead, CJ works with buyers like Imperfect Foods who buy the unwanted but perfectly edible green mandarins at a discount. But as the Imperfect Foods blog explains, when Fruit World green mandarins go to juicers, they sell them for so low that they can’t even recover the price of the box. If we welcomed green mandarins with open arms just as we do orange ones, CJ’s life would be much easier! 

I told CJ I’d love to buy his green mandarins. He was happy to hear from a green mandarin fan and now we’re both excited to see if we can start to change eater perceptions. Next time you talk to your citrus farmer or visit your local food market, ask about green mandarins (and oranges!). That way we can all start eating more green mandarins next October when the season starts. It’s a tiny, tasty way to help California citrus farmers thrive. 

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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.