Past the overgrown garden tangle, amid the cluttered kitchen and sagging ceilings and bathroom with no running water, a secret treasure glowed in Simon Mohr’s house.

Stacked against every wall were paintings, more than 300 in all, huge intricate murals in crimson and azure and tangerine and canary. They depicted life in every place Mohr had lived or traveled during a meandering, 88-year odyssey that took him from the Bronx to Haiti, Mexico, Pennsylvania Amish country and finally to Bowie, where he retired a few years back.

On Saturday, the vivid canvases were covered with plastic while a swarm of volunteers from the “Christmas in April” charity event, sponsored each year by Prince George’s County, went to work weeding, mulching, painting, plastering and repairing the broken plumbing.

Mohr’s home was one of 86 houses the county government selected for the one-day renovation and cleanup, which has been held every year since 1989. Officials said more than 1,000 volunteers participated, helping elderly and disabled homeowners throughout the county. Since the program began, volunteers have refurbished more than 2,000 homes and donated $35 million in supplies and services.

“I started painting when I was 9 and never stopped,” said Mohr, proudly showing some of his favorite works, signed with his nickname “Sy.” They included vast, whimsical murals of Port-au-Prince, Solomons Island and an Amish village. All vivid, crowded vertical scenes of houses, people, animals, shops, boats and other details of daily life, they were reminiscent of Rivera, Bruegel and some of Haiti’s best artists.

But somehow Mohr, who sold drapes and upholstery for a living, never seemed to have made any money from his artistic gift. Over the years, he said, he was periodically “discovered” and several of his paintings were hung in public buildings. But Mohr, who has suffered two strokes and lost his wife years ago, ended up living on Social Security in a house that was falling apart.

Scott Peterson, an aide to Prince George’s County Executive Rushern L. Baker III (D), said the county government learned about Mohr recently when the elderly artist called Baker’s office asking to show some of his work. After several visits, Peterson said, officials realized Mohr’s house was in desperate need of help — and that it also contained an astonishing trove of unknown but potentially valuable paintings.

“This is not just folk art. This is a great American artist,” said Samantha Vernon, an art expert from the county government who spent Saturday beginning to count, measure and list every painting in the house. “The problem was, he never had representation. He never had a market or a gallery,” she said. In other words, Mohr had no one to vouch for the value of his work.

Mohr seemed both dazed and emotionally moved as he wandered through the house and hovered in the garden, watching several dozen volunteers as they trundled wheelbarrows full of mulch and wielded paintbrushes on his ceilings. “You are doing God’s work today,” he told a group from a local Jesus Christ of Latter-day Saints church that had just finished whitewashing his living room.

His eyes welled up several times as he struggled to express his feelings or recall bits of history that had brushed his life. He repeatedly mentioned having met Eleanor Roosevelt and Louis Goldstein, the late politician who was the longtime Maryland state comptroller. He pointed out the name and face of his late wife, which he had painted into corners of his crowded friezes.

Mohr also spoke of his dreams for racial harmony and world peace, themes that figured in some of his murals. He said his greatest wish was to see his art shown or sold to benefit the people of Haiti and others who suffer.

“There has to be another way,” he said pleadingly, then gestured toward his teeming portrait of life in Port-au-Prince. “I never see color. I only see love.”