Where Do Citrus Fruits Come From? Check the Family Tree!

Our team at The FruitGuys is chock–full of fruit experts. We can talk your ear off about Ojai Pixie tangerines, wax eloquent about the difference between a mandarin and an orange, and discourse for days on genetically modified organisms (GMOs) versus hybrids. But when we set out to answer the question “Where do citrus fruits come from?” we found ourselves so tangled in a genealogical web that even we needed to call for backup. 

Luckily, the citrus pros at the University of California, Riverside (UC Riverside), came to the rescue. They worked with us to create the citrus family tree below, which will help you understand where your favorite citrus fruits come from and how they’re related to each other. 

Where Do Citrus Fruits Come From? 

“Most forms of citrus can cross with other forms. Some varieties have no seeds or viable pollen, and those are not easy to cross. Citrus has been around for 6–8 million years and has since spread and evolved in many different geographical and climatic areas,” David Karp, an assistant specialist in UC Riverside’s Department of Botany & Plant Sciences, told The FruitGuys.

Karp has tasted and photographed more than 800 citrus varieties from the Givaudan Citrus Variety Collection at UC Riverside and says pomology (the study of fruit) “offers the perfect marriage of art and science.” 

Here’s a quick guide to the tree to help you understand what you’re seeing. 

What Are the Original Citrus Fruits?

Generally speaking, all of the citrus varieties we know and love—like navel oranges, Rio Red grapefruits, and key limes—are descendants of five types of citrus. 

• Citron — These large, bumpy, yellow fruits often look like oversized lemons, with thick rinds and an acidic flavor. They also come in unique varieties like Buddha’s hand, which looks a bit like a squid with clusters of fruity tentacles or “fingers.”
• Citrus Micrantha — These tiny, bumpy, green fruits are native to the Philippines. They’re so bitter that locals typically don’t eat them, instead using the oil from their peels for fragrances.
• Pummelo — Also known as pomelos, these extra–large yellow–green fruits have an egg–like shape, thick rind, and sweet, mild flavor.
• Mandarin — These small, sweet, orange citrus fruits are fan favorites. Many varieties are easy to peel, and some are seedless.
• Kumquat —These tiny citrus fruits are the size and shape of grapes, with sweet skin and tart juice. 

All five of these types likely originated in Asia during the late Miocene epoch, about 6–8 million years ago. Fruit geneticists call this the Asian radiation. Over the centuries, they’ve produced thousands of offspring through hybridization (when one variety crosses with another) and mutation (when a natural genetic variation occurs within one variety). 

In our chart, the sweet orange is an example of a hybrid. It’s a cross between pummelo and mandarin. A navel orange is an example of a mutation. It’s a type of sweet orange that appeared naturally, essentially through a happy genetic accident. 

Mandarins, Tangerines, and Oranges: What’s the Difference?

Mandarins, tangerines, and oranges are all relatively petite orange citrus fruits with juicy segments inside. So, what sets them apart? 

Mandarins

Mandarins are one of the five original citrus fruits that all other citrus descended from. 

Tangerines

From our chart, you’ll see that tangerines fall under the mandarin umbrella. They’re not descended from mandarins; they’re a type of mandarin. Essentially, “tangerine” is another name for mandarins with deep red skin. 

“Mandarin is the much older term and is a biological term, whereas the term tangerine was a nickname given to brightly colored mandarins,” Dr. Tracy Kahn, the curator of the Givaudan Citrus Variety Collection at UC Riverside, told The FruitGuys. 

That means that while all tangerines are mandarins, not all mandarins use the nickname tangerines. 

Oranges

Oranges—both sour and sweet—are mandarin descendants. They’re hybrid varieties that appeared when mandarin naturally crossed with pummelo. We’ll talk more about sour oranges in a moment, but sweet oranges are one of the most well–loved citrus types. The navel orange, Cara Cara orange, and blood orange are all naturally occurring mutations of sweet orange. 

What’s a Sour Orange?

If you live in the Western Hemisphere, you’ve probably never seen the name “sour orange” when strolling through the grocery store. This pummelo and mandarin cross is one of the parents of the lemon, but it’s not nearly as tasty as its offspring. 

According to the US Department of Health and Human Services, “Its fruit is too sour to eat raw, but the fruit, peel, and essential oils are used in cooking, as flavorings in beers and spirits, and to add aromas to perfumes.” 

Karp told us that some fans of the sour flavor also use the juice. 

“Sour orange is common in some areas, notably the Caribbean, where its juice is used as a souring agent, much as limes and lemons are used,” he said. 

How Are Sweet Limes Related to Other Citrus? 

If you’re a sweet lime lover, you may have noticed that it’s missing from our family tree, even though we like adding it to our fresh fruit delivery boxes during citrus season. That’s because sweet lime’s heritage takes “it’s complicated” to another level. 

Sweet lime is a cross between citron and a mysterious mandarin and pummelo hybrid. That hybrid is likely extinct, and pomologists don’t have a name for it or know what it looked like. So, as much as we love sweet lime, we left it off our chart to avoid confusion.

How Do Finger Limes Fit Into the Citrus Family?

You may have noticed that we also didn’t list finger limes among the original citrus fruits, even though they don’t have any “parent” fruits on our chart. That’s because finger limes are part of what fruit geneticists call the Australian radiation—a more recent spinoff of the Asian radiation. 

The Australian radiation includes finger limes, round limes, and desert limes. It appeared in the Pliocene epoch between 5.3 and 2.5 million years ago. 

“Some people consider Australian finger limes as citrus, but others of us still consider it a citrus relative, Microcitrus australasica, so not in the genus citrus but closely related,” Kahn told The FruitGuys.

For simplicity’s sake, The FruitGuys typically refers to finger limes as a type of citrus, but the difference is worth noting.

Why Is Citrus Good for You?

Now that we’ve answered the question, “Where do citrus fruits come from?” let’s talk about something even more important—why they’re good for you. 

Eating citrus naturally boosts your mood with folate, enhances your immune system with Vitamin C, improves your digestion with fiber, and satisfies your sugar cravings. It’s also good for your heart, skin, and joints. 

In short, eating fresh and juicy citrus gives your mind and body a boost. It’s a great snack for the office—or any time or place. You can read more about the health benefits of citrus here and order it for your workplace here. 

More Citrus FAQs

1. How closely related are lemons and limes? 

Lemons and limes are both citron descendants, but how closely they’re related depends on the variety. Mexican limes, for example, could be seen as half–sisters of the lemon, while Persian limes (the common limes of the Western world) are a Mexican lime and lemon hybrid.

2. How are oranges and lemons related?

Lemons are a cross between sour orange and citron. They’re not directly related to sweet oranges, but they do share two common ancestors with them: mandarin and pummelo.

3. Which two fruits are oranges a hybrid of?

Sweet oranges are a cross between mandarin and pummelo. Sour oranges are a distinct variety but come from the same parents. 

4. When is citrus season?

Citrus is most abundant in the winter months, but there are exceptions to the rule. California farmers grow some varieties, like lemons, year–round. Other varieties, like the Valencia orange (aka summer orange), pop up in other seasons.

5. Can citrus be composted?

Yes! For tips on composting citrus safely and effectively, check out our citrus composting guide for office workers. 

6. Where can I order fresh citrus for delivery? 

The FruitGuys delivers fresh citrus and other fruits to offices and schools nationwide. Our Staples Mix includes citrus year–round, and you can find a wide range of citrus varieties (like Minneola tangelos, blood oranges, Page mandarins, and more) in our Harvest Mix and Season’s Best Box during citrus season.