Each day, Stan Kozak cultivated beauty that was as fleeting as its stately surroundings were permanent.
As the longtime chief horticulturist at the Isabella Stewart Gardner Museum, he spent his entire adult life overseeing flowers in the building’s memorable courtyard. While beautiful to behold, the stirring setting lets in little light and can often shorten the blooming life of floral displays.
“My only reprieve from the constant nurturing of plants is during the summer,” he told the Globe last year. “That’s when the hydrangea are in the courtyard — they last two to three weeks, as opposed to just five to seven days. I would love it if all the plants did that.”
Mr. Kozak, who joined the museum’s staff 50 years ago as a teenager and had been the Gardner’s top gardener for nearly three decades, died of cancer Sunday. He was 67 and had lived most recently in Stoughton, after formerly living in Westwood.
The job demanded unusual dedication, and his fidelity to the Gardner was legendary.
Eight or nine seasonal floral displays greet visitors each year, and some 300 to 500 plants are in the courtyard at any given time — driven into Boston from a greenhouse in Hingham. Mr. Kozak was ever-present as each display changed.
“His dedication here was unmatched,” said Mike Holland, director of facilities and capital projects at the Gardner.
“It was seven days a week. It didn’t stop on holidays,” Holland added. “He’d come in on Christmas. He’d come in on Thanksgiving. No one else in this building had the dedication to his craft and the museum that he did.”
Any ordinary gardener might be as spent as a fading flower after a few months of Mr. Kozak’s schedule, let alone five decades. His dedication continued even after he became ill, said Holland, who visited Mr. Kozak when he was in hospice care — and still inquiring about the state of the Gardner’s courtyard.
“I said, ‘Will you stop?’ He said, ‘I can’t,’ ” Holland recalled.
Mr. Kozak’s relationship with his floral charges went beyond the science of green thumbs, especially if something was amiss.
“Usually, I only talk to the plants when they’re not doing something they’re supposed to be doing,” he confided in a 2015 interview. “I use a stern voice.”
Peggy Fogelman, the Gardner’s Norma Jean Calderwood director, said in a statement that “few have had a more positive and sustained impact on the life of the museum and its capacity to instill a sense of wonder and solace in visitors.”
With the death of Mr. Kozak, she added, “The museum has lost a legendary presence who created magic for the Gardner, the city of Boston, and millions of visitors worldwide who have experienced our unforgettable courtyard.”
After first encountering the Gardner’s plants as a teenager, Mr. Kozak was tempted briefly by other paths before deciding the museum was his calling.
The older of two brothers, Stanley Paul Kozak was born in Boston in 1952 and grew up in Allston, a son of Stanley Kozak and Catherine Grace Driscoll.
Mr. Kozak studied agriculture in high school in Jamaica Plain and noted in a 1992 Globe interview that, along with serving as an intern at the Gardner, he had worked for a time with a landscaping company when he was young.
He told Architectural Digest last year that after high school, he had planned to study agriculture in college, until the senior gardener at the museum persuaded him to remain. Mr. Kozak joined the Gardner’s staff in 1969, and “the rest is history,” he said with a shrug.
Working at the museum was an education in itself. “I knew I could learn a lot from those guys who had been doing this for as long as I’ve been doing it now,” he told the Improper Bostonian last year.
In 1990, he became the museum’s fourth — and ultimately the longest-serving — head of horticulture, part of 50 years of service.
Some days, he took pleasure in the oohs and ahhs of visitors, particularly those who glimpsed the courtyard’s beauty and inhaled its fragrance for the first time.
“When the museum opens,” he told the Globe in 2015, “I like to stand here and listen to people say, ‘Oh, my God!’ ”
Often, though, he was his own most pointed critic, alert to flaws an untrained eye wouldn’t spot.
“Every year it’s something,” he said. “A fungus. An insect. We’re always battling them in the greenhouse.”
Keeping problems to a minimum was part of what drove him to work each day.
“Everybody took for granted that those plants were going to be out there,” Holland said, but their presence was because of Mr. Kozak’s rapt attention. “There were times when he felt like he had to sleep at the greenhouse because a particular species was on edge.”
On occasions when the museum’s staffing was short, Mr. Kozak would “put in 80, 90 hours a week,” Holland added.
In the 1980s, Mr. Kozak married Mary Hudson, with whom he had three children before their marriage ended in divorce.
“They remained committed co-parents,” their daughter Rebecca Golden of Stoughton said. “They would always say, ‘We have three children, how can we not be friends?’ ”
Gardner colleagues knew that “what was most important to him were his children. I can’t stress that enough,” Holland said. “And after that came his flowers.”
Mr. Kozak, Rebecca said, “was just an incredibly devoted and dedicated father. He would frequently bring us with him to the greenhouses and teach us and show us what he did for his work, so we were always spending time together. He was someone who could balance everything and do it all.”
When Mr. Kozak’s mother was ill at the end of her life, he cared for her.
“I had learned how to take care of a parent by watching him with his mother,” Rebecca said. “He certainly passed on his work ethic and love of family. That was really important to him.”
In addition to his daughter and his former wife, Mary Gillis of Dedham, Mr. Kozak leaves another daughter, Caroline of Huntsville, Ala.; a son, Stanley II of Stoughton; and a brother, Edward of Dedham.
A funeral Mass will be said at 10 a.m. Friday in St. Anthony Church in Allston.
At the Gardner, crowds marveled annually at the flowering nasturtium vines cascading into the courtyard from third-floor perches, heralding New England’s spring. Mr. Kozak, however, was fond of the hydrangea — not least because they lasted roughly three times as long as most other plants.
The purple and white blooms of a Miltonia orchid also caught his eye. “When they open,” he said, “they have a beautiful face.”
Legend has it that some of his plants’ shoots and cuttings traced their lineage to Isabella Stewart Gardner’s time, or nearly that long ago. That was enough to remind Mr. Kozak of his role in the history of the museum, and the city.
“Sometimes when I’m in the museum by myself, I have an eerie sense of someone or something near me. Especially when I’m alone in the Gothic Room,” he said last year. “It feels like Ms. Gardner is here.”