Amy Hagedorn, a philanthropist with a wide reach across Long Island and beyond, was the daughter and granddaughter of immigrants, a woman who came from humble beginnings and knew what it was like to struggle financially as a single mother of four after her first marriage ended.

She would later come into wealth, marrying the man who founded the popular Miracle-Gro gardening products, Horace Hagedorn, now deceased, and partnering with him on philanthropic endeavors.

Friends and family remembered Amy Hagedorn as a woman who never flaunted her wealth and who sought to use it to help others.

Hagedorn died Thursday at her Floral Park home of complications from lymphocytic leukemia, a chronic condition that her daughter, Lisa Valentine of Huntington, said her mother had “successfully fought” since 2009. She would have turned 80 on Sunday.

“Three weeks ago she had a rapid decline. It was devastating,” Valentine said. “But at the same time she knew she didn’t want us having to take care of her for years. She had a generosity of spirit like no other.”

Susan Hagedorn, of Denver, said of her stepmother, “What stands out is her generosity, her warmth, her pulling the family together, all of our families together ... ”

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A family biography of Hagedorn noted that while she was not born to wealth, when it came her way, through her marriage in 1986 to Horace Hagedorn, “she knew what to do with it: She chose to give it away through a foundation with a limited life span, making grants of meaningful size, to bring about real change on Long Island.”

Darren Sandow, executive director of the Amy Hagedorn Foundation, said in an email the foundation has given out $49,438,800 in 689 grants to more than 175 nonprofits since its inception in 2005. The Amy Hagedorn Foundation is scheduled to spend down its assets by the end of 2017. In addition, he said the fund Horace and Amy Hagedorn started at the Long Island Community Foundation in 1995 has given out $65,403,917 in nearly 2,985 grants to more than 500 nonprofit organizations.

Sandow, in an interview, said Hagedorn was “very engaged with the work, very engaged with our grantees.”

A former preschool teacher, Hagedorn was interested in early childhood education and in helping families. Her foundation also focused on immigration issues.

“She and her foundation joined together to fund national and state and local groups, all with the aim of achieving humane immigration policy,” said Geri Mannion, director of the U.S. Democracy Program at the Carnegie Corp. of New York.

“My mother was an immigrant. I identified with them,” Hagedorn said in the family biography.

Hagedorn’s mother, Angela Marchisella, came to the United States from Italy as an infant with her mother, sister and stepbrother, to join her father, Matteo. The family settled in Astoria, where Amelia Maiello Hagedorn was born in 1936.

Hagedorn graduated from Jamaica High School, then went to Baruch College. She married Joe Valentine, now deceased, in her junior year of college and had her first child in her senior year. She later studied at Queens College to become an elementary school teacher, the family said.

The family will have a private funeral service for Hagedorn and plans to hold a public memorial service at a later date.

In addition to her daughter and stepdaughter, survivors include sons Joseph Valentine of Bayville; Andrew Valentine of Hobe Sound, Florida; David Valentine of Douglaston; stepsons Peter Hagedorn of Maui, Hawaii, Jim Hagedorn of Sands Point, Paul Hagedorn of Atlanta, and Rob Hagedorn of Seattle; stepdaughter Kate Littlefield of Delray Beach, Florida; and several grandchildren and great-grandchildren.