Next to a field of sunflowers in Southampton is a house in which the towels, glasses, pillows, and even the bottom of the swimming pool bear images of the robust golden flower. And then there is the home’s owner, philanthropist and art collector Henry Buhl, who after a game of tennis at the Meadow Club on a recent Saturday morning, showered and changed into a sunflower T-shirt before sitting down to lunch with a group of friends.

Mr. Buhl’s East End outpost, named Girasole (“sunflower” in Italian), is one of the more cheerful examples of taking a decorating theme to an extreme. “It’s happy, uplifting,” Mr. Buhl said as he pointed to various examples around the house.

“I think it has more to do with the color than the flower,” one of the guests at lunch, Betsy McCaughey, said. “What Henry really likes is the color yellow.”

The yellow SmartCar in the garage would seem to confirm her theory, but Mr. Buhl is not one for long analysis of his taste, which — when it comes to sunflowers — seems to go beyond classifications of mood or color.

While traditional interpretations abound on fabrics and carpets that pair the golden petals with green and blue accents, the collection is eclectic. Above the fireplace in the living room is Mr. Buhl’s own photograph, a close-up of the pod of seeds in the middle of the flower, as if it were put under a microscope. On an adjacent wall is a large and mournful painting of a droopy black sunflower by an unknown local artist. And no, there’s no original Van Gogh in the house; the painting in the front hall is a reproduction.

The first sunflowers in the house came on a pair of andirons.They didn’t fit in when Mr. Buhl put them in front of the gigantic fireplace in his SoHo loft, but they seemed so right for his country home they set the motif. Twelve years later, and with the help of myriad guests who bring gifts for the house, the sunflowers are everywhere, including Mr. Buhl’s ties and his dessert table, thanks to a sunflower-shaped cake pan.

The front yard features large metal sculptures of sunflowers and an ornate gate to the 1-acre sunflower field. One of the most beautiful examples is on the entry doors in a design created and carved by an artist from Thailand. Mr. Buhl selected the artist after holding a design competition.

As a curiosity, the sunflower theme works well for large parties.Earlier this month Ms. McCaughey’s Committee to Reduce Hospital Infections held a fund-raising event there.

Those who know Mr. Buhl from the New York art scene know that sunflowers aren’t his only collecting obsession. The former investment banker and professional photographer who founded the Association of Community Employment Programs for the Homeless also collects photographs of hands, which in 2003 became an exhibition at the Solomon R. Guggenheim Museum in Manhattan. “Speaking with Hands” is currently traveling around the world. Perhaps there’s a connection between the shape of a petal and a finger. But in his homes, the themes are exclusive. Though he owns thousands of photographs of hands, visitors will not find them at Girasole, unless one counts the hefty exhibit catalog.

What is the sunflower-weary visitor to do? One sunflower-free zone is a guest bedroom that features a collection of antique birdhouses. On the edge of the yard is a lovely row of blue hydrangea bushes.And there’s always the clay tennis court — but only if one can disassociate the yellow tennis balls from the thousands of sunflowers nearby.