When it comes to stylish country living, Cordelia de Castellane, artistic director of Dior Maison and Baby Dior, has written the book. Quite literally. Life in a French Country House details the pastoral pleasures of her home near Senlis — a small rural town an hour’s drive from Paris — from planting tulips and picnicking in the forest, to water fights with the children, her “four musketeers” Stanislas, 21, Andreas, 18, Clélia, 11, and Vadim, 10.

De Castellane is the only artistic director to lead two departments at Dior. After founding a childrenswear brand with her cousin in 2006, she went on to design Dior’s children’s fashion collection in 2012, and five years afterward was appointed as the head of Dior Maison.

De Castellane’s love for gardens has earned her the nickname “Mrs. Flowers.” Climbing vines nearly obscure the guesthouse, at left.

De Castellane is discreet about her social circle, but the friend who contributed the introduction to her book is Natalia Vodianova, the supermodel married to Antoine Arnault, of the LVMH dynasty; she is also close to the designer Giambattista Valli and the family of Emanuel Ungaro, in whose atelier she began her fashion career, and is great mates with the British fashion designer Kim Jones of Dior menswear.

De Castellane, 40, bought her country house, parts of which date back to the 15th century, with her husband three years ago. The family soon realized that a country restoration would be very different from renovating a city home. “When you take a house in Paris you do everything new,” she says. “Here, when I put something new it wasn’t working.”

The boudoir, which was designed for intimate evenings at home, has its own dining table.

When it came to furnishing the interiors, she scoured flea markets and layered the rooms with her favorite French, English and Indian printed fabrics. New fabrics were dyed to make them look vintage, and men’s shirting adorns the hall and toile de Jouy one of the bathrooms. “The rule was, if it doesn’t match, it doesn’t matter. I just wanted it to feel like home, like it has always been there.” She incorporated heirlooms, from tableware to tiny silver boxes, and mined her extended family for more modest castoffs, including antique sheets. “Every time anyone in the family says, ‘I am going to throw that away,’ they know they can call me. In one of the bathrooms there is a little curtain that was a bedsheet belonging to my grandmother.”

She pays as much attention to table-scapes as she does to fashion design; the plates are some of her designs for Dior.

Weekends and holidays, and the whole of July, are spent in the French countryside. The house is not far from the polo hot spot of Chantilly, and de Castellane rides every weekend. But her primary passion here is horticulture. “Mr Dior was really attracted to flowers. He was living like me, in Paris in the week and going every weekend to the country. When he designed, he was remembering his childhood garden in Normandy.”

De Castellane declares herself “obsessed” with her flower garden (“some of my friends nickname me Mrs Flowers”), created by the UK-based landscaper Milan Hajsinek. “I’m a country girl at heart,” she says. “I grew up in the mountains in Switzerland and arrived in Paris at the age of 12, so the mountains and the countryside are very, very important to me.”

“I’m a country girl at heart,” says de Castellane.

Despite being at the center of the Paris fashion elite, de Castellane insists she is not a social animal. “I am very homely. I hate to go out. Even if I like to have my friends home for lunch and dinner, I’m happy too just with my flowers,” she says, having grown up an only child. Her regime in the country features few late nights. “I’m usually up at 6am and go to bed at 9.30, reading old magazines — I open them all and stick on Post-it notes. It’s very inspiring. I collect old interior design magazines from the Eighties — my mother got them all and I find the missing ones on eBay.”

As she approached the design of her home, de Castellane was inspired by interiors magazines from the 80s.

During the winter months, she hunkers down here even more. “At night I do embroidery in front of the TV with the kids, while they watch a movie,” she says. “Saying that, I have this huge family with lots of cousins. We are Greek, Spanish and French. When we get together, there is flamenco dancing late at night and singing in Spanish, there are the Greek weddings where they dance sirtaki and break the plates on the floor. So I promise you, I am fun! Sometimes.”

Katrina Burroughs is the interiors editor for The Times of London and The Sunday Times