Strolling through his 74-acre estate on a sunny day in May, Joseph Mul can tell what his roses need at a glance. His family has grown flowers on the same land for six generations outside Grasse in Southern France.

"When I started, we worked with horses," Mul, now in his 80s, says in French. "There weren't any tractors."

His family supplies the roses and jasmine that give the cult-classic perfume Chanel No. 5 its signature scent. In 1987, as Grasse's perfume industry was waning, Chanel's perfumer at the time, Jacques Polge, helped secure an official partnership with the Mul estate, which had already been supplying to the brand for decades. Today his son and successor, Olivier Polge, continues working with the Mul family to preserve the flowers' distinct scent.

Mul has watched many of the region's flower farmers disappear over the decades, squeezed by cheaper foreign competition and soaring land prices that made selling fields to property developers far more lucrative than cultivating them. As the estate's owner, he still walks the fields each day with his son-in-law, Fabrice Bianchi, the director of operations, and granddaughter Marika Bianchi, the chief of cultivation.

"What I love most is planting something new," he says. "You put a tiny plant in the ground and watch how it grows. That's what's truly beautiful."

Here, translated from French, Mul discusses the future of flower harvests in Grasse, passing forward the family business and what goes into creating Chanel No. 5.

How did your family business begin?

My family started planting roses and jasmine in the 1870s or 1880s. Grasse became the world's center for perfume essences [the concentrated aromatic extracts used to make perfume]. Not for perfume itself-for essences. At the time, very little perfume was actually made in Grasse.

Did joining the family business feel like a choice or an obligation?

It was always natural for me. I was always at my father's heels, so I naturally picked up all his passions-hunting, fishing, the outdoors and sports.

What was the most important lesson your father taught you?

He taught me many things, but what I remember most is the conflict between generations. At first, he'd tell me, "You're in charge of this." Then he'd say, "No, don't do it that way."

That's the kind of friction every generation goes through. I went through the same thing with my son-in-law. The person taking over the business has to be allowed to lead. There will always be discussions-that's normal, especially in agriculture, where you're constantly adapting to the unexpected. But if the older generation keeps overruling the younger one, that's when conflict begins.

What has stayed the same since you started working here, and what has changed?

The harvest is exactly the same. It will always be the same. We still pick the flowers in the same way, but we've evolved with agriculture. You have to adapt to new techniques and new knowledge. In the past, we'd analyze the soil every two or three years to check whether everything was balanced. Today, we can do it much more quickly and much more often. That lets us better understand the challenges the plants face.

What's your favorite part of the job?

New plantings. That's the creative part. Now I'm no longer on the front line; that's the next generation's role. My job is mostly to observe. You prune in the middle of winter, then you watch the new growth and follow its progress. Every day, we observe what's happening and discuss it. But in the end, the person on the front line is the one who makes the decisions.

How would you describe Chanel's approach to sourcing its flowers?

Chanel has always been committed to keeping its fragrances unchanged. To do that, it has to use the same exceptional ingredients that were used to create them. You have to know you'll be able to keep sourcing those essences. Otherwise, there's no point. People who wear the fragrance will notice.

How do you pass on your experience to the next generation?

We challenge each other every day. Everyone brings their own ideas, and we discuss them based on our experience and what we're still learning. That's how we pass things on: through open, honest discussion, without raising our voices.

What do you think it will take for these fields to still be here in another six generations?

I'll tell you one thing: If we hadn't made these agreements with Chanel, we might not still be growing these flowers today. In the 1970s and '80s, many fragrance companies turned to other sources. Compared with jasmine grown in places like Egypt, we're a hundred times more expensive-not because of the way we grow it, but because of the cost of labor. Companies moved production abroad, but they don't get the same quality we do here.

Your son-in-law now runs the business. How did that transition happen?

My son-in-law didn't come from an agricultural background. When he got married, he said, "I want to come and work with you." It was the same with my cousins-they all wanted to join the business. Little by little, everyone found their place. One of my cousins works at the factory, another son-in-law is at the factory, my niece looks after the aromatic plants, and my daughters work in the office. Everyone in the family has their own role.

What was it like stepping back?

[Fabrice] spent several years learning every part of the job. Then, as always, there was a bit of conflict over priorities. Finally, I told him, "From now on, you're the one who sets the priorities and takes care of the rest. I'll be here to support you." And that's how the transition happened.

What does it mean to have your children and grandchildren working alongside you every day?

You know, when you see your children every day, you're happy. It's not like in many families, where one child is in Paris, another in New York, another somewhere else. I have the good fortune of having my children and my grandchildren all here around me. That's priceless. At my age, having everyone together like that is extraordinary.

This interview has been edited and condensed for clarity.

Header video by Iris Humm for WSJ. Magazine