Andrea Wulf looks right at home in the U.S. Botanic Garden conservatory — a couple of hours off a plane from Atlanta, fresh from an interview for “All Things Considered,” the horticultural historian poses for a photographer amid the palms and the orchids and a thousand other tropical flowers.

Wulf’s new book, “Founding Gardeners,” recently reached No. 32 on the New York Times bestseller list. An unlikely feat for a gardening history, but Wulf has hit on something: She’s taken a quartet of iconic American figures and wrapped them in the zeitgeist of the postmodern victory garden. Her book argues that George Washington, John Adams, Thomas Jefferson and James Madison were all dirt-under-the-fingernails gardeners whose love of the soil shaped the way they forged a nascent country.

A German with impeccable English, she repeats the same yarns, in her talks, in her press interviews, in the book, of course; but face to face, one-on-one, the stories seem so spontaneous and deeply felt that you believe that this is more than an author’s promotional script.

“Adams is building stone walls,” she says, kneading the air with her hands. “Washington dies a gardener’s death.” How does a gardener die? Does he throw himself on the compost pile? No, he goes outside when he is sick, on a foul December day, to mark trees for cutting. He is the one felled.

Wulf has retreated to a quiet room in the conservatory where she warns me off the house coffee and talks for two hours about the zeal of her subjects. Their zeal is her caffeine.

“Their passion for planting, gardening and agriculture is deeply woven into the fabric of America and totally aligned with their political thought,” she says.

For years now, the stewards of Mount Vernon and Monticello have played up the idea of gardening and agriculture as being central to their heroes’ stories. At Mount Vernon, we have the greenhouse and its ornamental garden, the dockside colonial farm and the innovative threshing barn. At Monticello, America’s most majestic fruit and vegetable garden has been rebuilt and lovingly cultivated.

Wulf’s book validates that take, but she also examines the lesser-known exploits of Adams, who credited gardening at his farm in Quincy, Mass., with giving him the mental strength for politics. As the minister to London, he complained that the social life of a diplomat to be “an insipid round of hairdressing and play.” On the fringes of the British capital, he once delighted in finding a compost pile to examine. “Teasing apart the straw and dung,” Wulf writes, Adams “clearly didn’t mind the muck on his hands.” He noted “with glee that it was ‘not equal to mine.’ ”

Madison emerges as the proto-environmentalist, sounding an early clarion against the perils of depleting soil by clearing forests and overfarming land. He urged his fellow Virginian farmers to protect the old-growth forests. At Montpelier, he staged “the forest as the main feature,” Wulf writes. “This was an approach that celebrated the American landscape as it was rather than creating something entirely new and European.”

For generations, historians have been peering into the republic’s pantheon through their own prisms. Wulf says that in a more deferential age, it would have been considered disrespectful to regard America’s revolutionary heroes as gardeners. To do so now, she says, provides a richer understanding of what drove the nation’s architects.

“Not only did they create the United States in a political sense,” she writes, “they had also understood the importance of nature for their country.”

The White House grounds, she writes, relatively small and enclosed, were the work of Jefferson. As an anti-Federalist, he did all he could to doom earlier plans to build presidential gardens at 1600 Pennsylvania Ave. L’Enfant had wanted a 60-acre palace garden — as president, Jefferson grabbed just five and gave the rest to his fellow citizens.

Reviews of the book have been abundant and mostly positive. In the New York Times, Paula Deitz called it “revisionist in the best sense.” But the high-profile historian Simon Schama, in a review in the Financial Times, assails the whole premise of “Founding Gardeners.” The book, he argues, “could have used more reflection on ways in which horticultural fantasy skewed the American mind towards the entitlement of bounty — usually on the backs of the exploited.”

Wulf remains convinced, passionately, that the first presidents “were more than just farmers and gardeners, they were some of the most revolutionary farmers in the country.” A reinvented system of agriculture, geared to the needs of a young and abruptly isolated country, “is for them a republican endeavor.”

Monticello’s Peter Hatch, an expert on Jefferson the gardener who got to know Wulf as a frequent visitor to Monticello during her research, says the book breaks new ground, including its accounts of Jefferson and Adams touring gardens in England, and of Jefferson and Madison doing the same in New England.

It was at Monticello — Wulf remembers it vividly — that the idea for the book suddenly gelled. Working on a previous book about 18th-century English gardeners and their interest in American plants, “The Brother Gardeners,” she found herself in Jefferson’s vegetable garden one quiet day in October 2006 and was struck by the natural beauty of the mountain in autumn against the rigid geometry of the vegetables. “It clicked,” she said. “Oh my God, he’s a complete gardener.” That passion was evident in letters of the others, too, she said.

Wulf spent the first five years of her life in India — her parents worked for a German aid group — and grew up in Hamburg. She is 43 but looks much younger, and her daughter, Leanne, will turn 21 later this month. She describes herself as a single mother.

She moved to London in the mid-1990s and, after a couple of years, opted to study design history at the Royal College of Art. “Suddenly I was there for four years. I decided to stay.” Her daughter was settled in school, and Wulf felt quite at home. She likes the British sense of humor and sarcasm and could engage in English society without the native’s class baggage. She said after 15 years in Britain she considers herself more as a European than a German. Hatch calls her “English with a German accent.”

On her first visit to America, she recalls, she and her father embarked on a seven-week road trip to the West Coast. The land was vast, the highways endless and straight, even the cartons of orange juice were at least twice the size of Europe’s.

“It confirmed every cliche a German teenager had,” she said. “I never thought of America as a gardening nation.” That view changed when she researched “The Brother Gardeners,” which she wrote to get her head around the English obsession with plants.

Speaking to garden groups — her 35-city tour began in early April and lasts through mid-June — she sees in America an abiding connection to the soil. “There’s an incredible, almost visceral feel for the dirt here, which I don’t see in England much,” she said. At this point, her hands are not just dancing, but shooting into the air. Golden zippers on the underside of her coat have been pulled back, and on the inside of her wrist, there is a modest tatoo, the letter L with curlicues. For her daughter, she explains.

But she’s more comfortable talking about America’s past than her own present, except to say her next book is on the transits of Venus in the 1760s. For now, though, she has the magnificence of manure on her agenda. “I regard gardens as a prism to look at science, culture, art,” she says.

“I’m sort of an 18th-century girl.”