John Hoke was fired from the federal government in 1962 because he wanted to build a boat powered by the sun.

Posted to South America with the U.S. Agency for International Development, he devised a collapsible watercraft that would run on solar energy. He said the boat, gliding along at three miles an hour, would carry him up the rivers of Suriname on a diplomatic mission to install radio receivers in far-flung villages and win friends among indigenous tribes.

When the boat’s $28,000 price tag reached the U.S. House, a livid representative from Virginia said Mr. Hoke’s scheme appeared to have emerged straight from “never-never land.” The congressman demanded Mr. Hoke’s dismissal and ordered a wider investigation of USAID’s expenditures.

Some years later, the Army tested the solar-boat design, Mr. Hoke told The Washington Post, and found that it functioned “exactly as I said it would.”

John Hoke, a writer, naturalist and inveterate tinkerer, was 85 when he died Feb. 25 of respiratory failure at his home in Bethesda. He spent much of his life dreaming up ideas that the world wasn’t quite ready for, but his unconventional thinking did succeed in turning some of Washington’s barren and stinky decorative pools into living ecosystems crowded with turtles, fish and waterfowl.

He eventually worked his way back into federal service with the Interior Department , where he was charged with helping to manage Washington’s urban parklands. For decades, he was known as the cigar-chomping fellow who rode around in an electric golf cart, patrolling the Mall and environs.

In the winter, he favored a Sherlock Holmes-style cape that fit his 6-foot-5 frame. During summer, he fended off the heavy humidity with a solar-powered, air-conditioned pith helmet of his own invention.

In 1977, Mr. Hoke campaigned to persuade government officials to install a garden atop the Interior Department’s seven-story D.C. headquarters. The rooftop refuge would save heating and air-conditioning costs throughout the year, acting “as insulation,” Mr. Hoke told The Post at the time, “just as the earth roof of a yurt keeps it warm in winter and cool in summer.”

He envisioned a time when the city’s office buildings would all be topped with soil, trees and birds. “The roofs of Washington are a vast undiscovered country,” he said, “and here we have an opportunity to put back — eight, 10, 15 stories up in the air — the natural environment we destroyed and stripped bare on the ground.”

His vision languished for more than three decades, until 2008, when Interior Department officials cut the ribbon on a new green roof, hailed in news releases for its insulating effects and other benefits.

Bureaucrats did occasionally listen to Mr. Hoke. At his insistence, the National Park Service bought a fleet of electric golf carts for traveling around Washington area parks. Mr. Hoke had proved the carts’ hardiness by using one to journey the length of the C&O Canal, more than 180 miles from Georgetown to Cumberland, Md.

He was perhaps best known in Washington for his madcap and ultimately brilliant effort in the late 1960s to relocate tons of mud and marsh plants from Kenilworth Aquatic Gardens to Simon Bolivar Pond at 18th and C streets NW. He brought turtles, too, that he and his children had found injured on rescue missions around Washington.

“We’d fix them up and put them in a perfect welfare state,” Mr. Hoke said. “They lend a certain class to the place.”

The result was an astonishing conversion of the pond from an algae-choked and odoriferous body of water into a clean and self-sufficient marshland ecosystem.

Soon ducks and geese were frequenting the pond, and it became the prototype for other ponds around town — including one at Constitution Gardens along the Mall, where enterprising urban anglers have been known to land bluegills and largemouth bass.

The rehabilitations saved the government thousands of dollars annually, since the ponds didn’t have to be drained, cleaned and refilled several times each year. Mr. Hoke received a Meritorious Service Award from Interior for his work.

When he retired in 1991, no one knew quite how to describe his job. Newspaper accounts called him a “biological engineer” or an “urban parks specialist.” His co-workers called him “Lord Hoke.”

“I never really worked at this place,” he said at his retirement roast. “I just came aboard, did things, and they paid me for it.”

John Lindsay Hoke was born June 26, 1925, in Pittsburgh. His father was a musician and editor. His mother was a writer who established a successful children’s book publishing house.

Mr. Hoke graduated from Antioch College in Yellow Springs, Ohio, in 1950 and then went to work as a photographer for the American Automobile Association in Washington. On the side, he indulged his interest in the natural world by writing a dozen books published by his mother’s company: “The First Book of Snakes,” for example, and “Turtles and Their Care.”

He joined the federal agency that became known as USAID in 1957. In Suriname, he became enamored of three-toed sloths after one bit him. He brought a sloth back to Washington, named it Lady III and donated it to the National Zoo.

After losing the USAID job, he made an electric car — retrofitting a boxy old King Midget kit car — for less than $1,000. The vehicle had a top speed of 35 mph and could run 20 miles between charges, according to Life magazine, which ran a photograph of Mr. Hoke standing in his suburban yard in 1966, preparing to plug in his car.

The Hoke home in Glen Echo Heights had indoor and outdoor ponds filled with critters, including a plethora of pet snakes. It was a magnet for neighborhood children and a glorious place for Mr. Hoke’s four children.

“We had so much fun,” said Edward Hoke, recalling how he and his siblings and a gaggle of other kids would join Mr. Hoke in wading into C&O Canal muck up to their necks, looking for turtles. “He never grew up. He was just a kid his whole life.”

Besides Edward Hoke, a Washington resident, survivors include three other children, Lawrence Hoke of Denver and Franklin Hoke and Bonnie Hoke-Scedrov, both of Philadelphia; and five grandchildren.

Also surviving is Mr. Hoke’s wife of 60 years, Sylvia Hyde Hoke of Bethesda, who joked at Mr. Hoke’s retirement party that it was “a little frightening” to think of having him and his crackling energy at home full time.

In recent years, Mr. Hoke continued to work on various projects in his basement shop. He never lost his fascination with alternative energy.

Once, he lured baby squirrels into his house, fed them and then hooked up the running wheels in their cages to electric generators.

“You’ve heard of two cars in every garage?” his longtime friend Joe Goodwin told The Post in 1991. “John wanted every house to have 20 squirrels.”