Irvin Williams, whose horticulture career spanning the Kennedy to the George W. Bush administrations made him the longest-serving gardener in White House history and who was a key figure in the creation of the Rose Garden, died Nov. 7 at a hospital in Reston, Va. He was 92.

The cause was renal failure, said a son, Bruce Williams.

Mr. Williams, tall and dapper, with a silver mustache as groomed as his South Lawn greensward, was averse to publicity during his 46-year tenure but had a pivotal role in maintaining the continuity and integrity of the historic landscape — and making sure the turf was repaired after the annual Easter Egg Roll.

He was appointed White House head gardener in 1962 and retired in 2008, but as a government horticulturist, he had worked on White House garden projects going back to the Truman era.

While charged with installing such landscape additions as President Gerald R. Ford’s swimming pool and first daughter Amy Carter’s treehouse, he did so without compromising the master plan laid down by landscape architect Frederick Olmsted Jr. in the 1930s, said historian Jonathan Pliska.

Mr. Williams knew each of the 400 trees on the grounds and led a team charged with preserving specimens — or propagating their offspring — going back to the time of President John Quincy Adams.

“No president, maybe except for Thomas Jefferson, has had as big an impact on the garden as Mr. Williams,” said Pliska, author of “A Garden for the President.” “He’s on the Mount Rushmore of who’s contributed the most, and he’s unfortunately one of the least known. But that’s how he wanted it.”

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Although he had little formal training, Mr. Williams’s horticultural skills, work ethic and high standards secured him a spot as superintendent of the District’s Kenilworth Park and Aquatic Gardens, where the White House had its working greenhouses. From the mid-1950s, he was regularly assigned to landscape projects at the White House and took up his full-time supervisory post there in 1962.

Mr. Williams was the last surviving member of the team behind the modern-day Rose Garden.

Early in his presidency, John F. Kennedy wanted a complete reworking of the West Garden outside the Oval Office to establish a space that could be used as an outdoor stage for ceremonies. The old garden was a dull confection of clipped privet hedges, and the narrow steps connecting it to the president’s office were an awkward spot for addressing crowds.

Kennedy turned to his wife’s friend, arts patron and garden designer Rachel “Bunny” Mellon, to design the new garden. Mellon, in turn, sought design counsel from society landscape architect Perry Hunt Wheeler. She had just four months to create a design and build and plant the garden.

“Her approach was to find an individual she could communicate with, one who knew horticulture and gardening, could manage a work crew on short deadlines, and was aware of the particular and sometimes peculiar ways of the White House,” historian William Seale wrote in the journal of the White House Historical Association. “It seemed at first a daunting task, but it did not turn out to be. Close at hand was Irwin M. Williams.”

The new garden featured broad steps that could be used as a stage, a central lawn for assembled dignitaries, and a framework of ornamental trees, boxwood hedging and rose bushes for the seasonal plantings that provide color from April to November. (He planted at home the same rose varieties as the ones he placed in the Rose Garden so that he could master their cultivation.)

Mr. Williams was an expert in digging and moving mature trees, and he brought four large saucer magnolias from the Tidal Basin to the Rose Garden to mark the garden’s corners.

After Kennedy’s assassination in November 1963, Mr. Williams worked with Mellon to renovate the East Garden on the other side of the South Portico, dedicated to Jacqueline Kennedy during the Johnson administration.

“He was a consummate servant at the palace,” Seale said in an interview. “His only interest was doing his job well and right, and he was very particular.”

Irvin Martin Williams was born in Engle, W.Va., on March 18, 1926, and was the son of a farming family that moved to Northern Virginia when he was a boy.

Survivors include his wife of 67 years, Dorothy Dailey Williams of Herndon, Va.; children Donald Williams of Lorton, Va., Gary Williams of Richmond, Richard Williams of Herndon, Bruce Williams of Arlington, Va., and Patricia Williams of Paragon, Ind.; and eight grandchildren.

In retirement, Mr. Williams propagated boxwood, and over the years, he became a collector of antique clocks and the lead crystal vases used to adorn luxury automobiles.

Even to family, Mr. Williams spoke little of his interactions with presidents. He asked one of his grandsons to gather acorns so President Ronald Reagan could feed the squirrels in the Rose Garden.

But Mr. Williams had a love-hate relationship with the squirrels that each fall eyed the many thousands of newly planted tulip bulbs as an invitation to a feast. Ever the pragmatist, Mr. Williams would place containers of peanuts at the base of the trees to appease the furry marauders. (At heart, he was a pet lover who adopted Pushinka, the puppy Soviet leader Nikita Khrushchev had given to the Kennedys.)

Mr. Williams helped presidents install their personal landscape elements, and after assisting George H.W. Bush in building his horseshoe pitch, he would sometimes join the president in a game.

Fortunately, Mr. Williams didn’t have to play down. “Mr. Bush was really good. My father tried to beat him but never could,” Bruce Williams said.