Just off one of the busiest intersections in Riverside stands a tree that changed Southern California forever.

Born more than a century and a half ago, this tree began as a chance mutation in the garden of a Brazilian monastery.

From Brazil, it traveled by ship to a USDA greenhouse in Washington, DC, and from there by train, stagecoach, and buckboard wagon to the farm of Luther and Eliza Tibbets.

As the story goes, Eliza nursed the young plant through Riverside's hot summers with leftover dishwater.

It survived, and this tree, along with its long-lost sibling, became the ancestor of nearly every navel orange grown in California.

Welcome, Nathan.

Thank you.

Thanks for meeting me here.

Absolutely.

Come inside, but don't take too many steps.

This is a maximum security fruit tree.

Georgios Vidalakis, a plant pathologist at UC Riverside, works with Sohrab Bodaghi and other members of his team to not only protect this historic tree from disease and pests, but the entire global citrus crop as well.

You see, this is the trunk, the original trunk, the 1873 trunk.

Wow.

You see how this looks a little bit better than this section?

-Yes.

-This is what we call a Phytophthora lesion.

The fungus-- actually, it's not a true fungi, it's what we call an oomycete, almost killed, completely did what we call girdling the tree.

Then the wood inside is there that moves water up and down.

When the bark dies, the tree dies.

If by girdling, you mean if it went all the way around, that's the end of the tree.

-Exactly.

The tree did its best and stopped it right there.

This is what we call healing tissue, but it needed help.

In the 1920s, the University of California came in, and we did what we call inarching.

We planted young seedlings around the tree, and the original tree started using the roots and the bark, you see how this bark is not injured, and feeding itself.

There's so much more engineering behind this tree than you would ever realize.

It does not just grow and survive on its own naturally.

No.

Unfortunately, it would have died if science hasn't intervened.

This is a beloved tree.

You're actively taking care of this, helping it survive.

Oh, yes, absolutely.

The general rule is that because this belongs to the city of Riverside, and this is a tiny park.

Actually, it's designated as a park.

They can come and clean and pick up the leaves, but nobody touches the tree other than, actually, PhDs, people with doctorates that they know what they're doing.

-You need a PhD to touch this tree.

-Oh, absolutely, yes.

We don't allow anybody else.

Science has spent half a billion dollars trying to find solutions to these problems.

That's largely because it's a huge multi-billion dollar industry, growing fruit.

-Absolutely.

Why, say, this tree?

I believe it was 2020 that an economist did the study.

The California industry alone is estimated of a value of $3.6 billion, economic activity to close to $8 billion, and essentially all of it can be traced back to this tree.

This beautiful fruit from California was sold all the way to the East Coast of the United States.

-They were wrapped in tissue, right?

-Oh, yes.

They were precious.

It was like a Christmas gift.

You will get a California-- Actually, they were called back then the Riverside Navels.

These were delicacies.

These were luxuries.

Today, you can buy these by a few dollars a pound, but back then, this was a holiday treat.

Correct.

Absolutely.

Because the variety was introduced from Brazil to the United States through Washington, DC, Sanders was the name of the gentleman that made the connections with missionaries down in Brazil.

-At the USDA.

-At the USDA.

If I remember well, they put 12 in a box.

A lot survived.

He propagated even more.

He sent these trees, he sent them all over the country, not only in Riverside.

San Francisco, San Diego, Florida.

Again, that very old report from USDA said the other trees didn't do well, but the Riverside one flourished.

Like today, Southern California has always been a melting pot.

You can see actual pictures of people working with the tree or trees, and they're immigrants from Asia, from Europe, where citrus existed for thousands of years.

I want to believe that a little bit diverse community of Riverside.

Plus, I met, a few years ago, a senior of the Cahuilla people, the local Native American people in our region.

He told me, "Georgios, yes, and it's been part of our tradition as well.

When the citrus industry took off, it was our people that knew where the water is, where the fertile ground is."

It's a community team effort for me.

That's why this tree was successful.

That's really interesting.

When we talk about the success of citriculture in Southern California, we talk about the physical landscape usually, but the cultural landscape, you're saying, was just as important.

Absolutely.

This is the perfect place to grow citrus, no question about it.

There you are.

You are doing great.

-Oh, yes.

-Ready?

-Yes.

-Cheers.

Cheers.

150-year-old tree.

The fruit is-- -It's beautiful.

-Yes.

Shall I come close?

[laughter] The citrus boom that this tree launched needed science to sustain it.

In 1907, University of California researchers established an experiment station, first in Pomona, then here in Riverside, to study and develop the region's most important crop.

Three years later, they began assembling an unrivaled collection of citrus trees that's been growing ever since.

Today, the Givaudan Citrus Variety Collection at UC Riverside holds 4,500 trees representing nearly 1,100 cultivars.

I went to meet its curator, botanist Tracy Kahn.

This collection today, it's part of UC Riverside.

Yes.

In some ways, this is the forerunner to UC Riverside.

It's the reason UC Riverside is here.

That was more than 100 years ago.

There's no collection in the world like this.

There are collections associated with universities, but most of them are nowhere near this diverse.

You couldn't build a collection like this from scratch today.

No, I think it would be really difficult to breed a collection like this.

I think that's why it's so very important to make sure it gets preserved, not only for what we can use it for, but to have that history and to have that understanding of the diversity of citrus.

Now I see you have here the Washington Navel Orange.

This particular variety does loom large in the lore of this place.

It does.

This is a publication from 1933, a citrus publication.

It was from the Riverside Chamber of Commerce, which connects it to this location as well.

This is the one where they honor Mrs.

Eliza Tibbetts for planting it in 1873.

The origins of it are all shrouded in mystery.

There's also, it's curiously, Luther Tibbetts is not represented here.

He's more or less been written out of the story.

Right.

I got to take this really cool class at UCR when I was a graduate student here.

It was taught by a guy named Bill Bitters, who was the curator before me from 1946 to 1982.

He taught us in this class about the parent Washington Navel.

It's connected to Riverside.

This is one of the things that he kept.

This is actually his handwriting, which is one reason I kept it.

-Oh, yes.

You got to keep that.

-People used to argue about which year it came.

This one confirms that it was December 1873.

It said that there were two trees, but apparently that was wrong.

There were actually three trees.

I've heard that, yes.

On page 138, it talks about the three trees that were planted in 1874.

One of those trees, and it talks about on page 139, was actually trampled by a cow, as how I learned it, but by cattle, and it died.

What we usually think about is two trees, and some places write just about those two trees.

Yes, we don't talk about the third tree.

This one, I guess from page 127 to 161, it talks about Luther's role in the whole thing as the founder of the navel orange.

Eliza's family actually pushed her as being the founder.

This article shows that on page 145, that she didn't arrive until two years after the trees did.

Whatever the truth of the matter, there was this generally accepted mythology around the origin, and I can imagine that had a lot more importance, say, in 1920, when Riverside was still this huge citrus-producing community, and not only Riverside, but Redlands and Pomona, and it was part of the region's identity.

Definitely.

It was the first one that was brightly colored, sweet, fairly easy to peel, and had no seeds.

It was something people were really excited about.

You have two of these parent Washington navel trees right over here.

I have four.

Two trees, one from each of the two original trees.

Wow.

Okay.

Let's go take a look.

Okay.

These are navel oranges, then?

These are navel oranges.

In fact, at the time these were originally propagated, we still had two trees in Riverside.

Now we only have one of the original trees.

The other original tree was transplanted to the grounds of Riverside's Mission Inn by President Theodore Roosevelt himself, a fitting honor for the most economically significant tree in California history.

It survived there for nearly two decades before disease claimed it in 1922.

We've got fruit here.

We've got some really big fruit.

Oh, yes.

Those are big fruits.

Wow.

-These are big fruits.

That's a big orange.

That's a big orange.

This is almost the size of a grapefruit.

There we go.

Oh, yes.

You can really see in this one.

It's great.

This is an orange inside an orange.

This right here is why we call it a navel orange.

It is.

In fact, this is the best example I've seen in a long time because you can actually see the rind of the smaller orange inside the larger orange.

We just got lucky by pulling that off the tree.

Yes, we did.

You want to taste and see?

-Yes, let's do it.

-You can smell it, but it's-- -Yes, quite fragrant.

-There you go.

-Oh, thank you.

It tastes just like the orange, like the Tibbetts tree orange, which makes a lot of sense because it's essentially the same tree.

Right.

That's good.

I'm glad you've tasted both in the same day.

That's delicious.

Wow.

Not many people can say that.

No.

This orchard doesn't just preserve the past.

It's the Silicon Valley of citrus, a hub of innovation where new varieties are born.

The Tango mandarin, which you may know from the supermarket as a cutie, was developed right here.

Of course, not every discovery happens in a lab.

Or a research orchard.

The Cara Cara was a natural mutation first spotted on a farm in Venezuela.

This right here looks like a navel orange tree.

It is.

It's a navel orange tree, but it happens to be a cultivar that we call Cara Cara.

Okay.

Oh, wow.

I can already see.

It's pink.

It's like a grapefruit almost.

Yes.

It's the same pigment in pink grapefruits.

It's called lycopene.

It's the same pigment in tomatoes, too.

Lycopene.

-Really?

Wow.

The pink adds a little visual interest.

Does it taste roughly the same?

-It does.

You want to taste it?

-Yes, please.

Okay.

There you go.

-Oh, thank you.

Yes, it's good.

It tastes the same.

It's pink.

I think on the way over here, we passed what looked like a mandarin tree.

-Yes, this is a mandarin tree.

If I'm not mistaken, it's essentially one of the ancestors of what we know as the orange.

We don't know if this particular tree or cultivar is an ancestor, but we know that based on its genetics, that yes, this type is in the ancestor group of mandarins, which are not most of the mandarins you're eating from the store.

Most of the mandarins you're eating from the store, like clementines or tango, they have a little bit of pomelo genes in it.

Oh, they do.

This is a pure mandarin.

This is a pure mandarin.

The orange, is it a hybrid of the mandarin and the pomelo?

Happened way before humans were around, but yes.

Do you think we could pick one of these and pick one of the pomelos and taste them together?

We could.

We could do that.

Let's take a couple.

These are small, yes.

We're going from a tree with really small fruits to a tree with some pretty big ones.

Right.

This is called Mauna Loa pomelo.

-Oh, my goodness.

-There we go.

[laughs] Essentially, the orange is a cross between the pomelo and a mandarin.

It wasn't just one cross.

We're talking about huge amounts of time.

Since citrus probably originated about 8 million years ago, there were crosses back and forth, back and forth.

There was lots and lots of time that generated what we think of as sweet oranges.

Then sweet oranges are all genetically very similar.

They're 99% genetically identical, but that includes things like the navels, but also blood oranges.

That 1% can make quite a bit of difference.

-Right.

Are you going to have it with me?

Okay, let's go.

Actually, that's pretty tasty.

It's not too bitter.

Mandarins have that characteristic where they just fall out of their peel.

Oh, yes.

These are some little guys here.

Wow.

I'm going to have one little.

You can see how a cross between this fruit here and this fruit here could produce an orange.

[laughter] I don't think I've ever done that together.

There you go.

I'm glad.

You've probably done all things citrus under the sun.

Yes.