A longstanding and unprecedented gift of 156 acres at Quansoo Farm in Chilmark from the late Florence (Flipper) Harris to the Sheriff’s Meadow Foundation is now complete, leaders at the foundation announced this week.

Donated to Sheriff’s Meadow by Mrs. Harris over a period of years beginning more than a quarter century ago, the Quansoo Farm gift is the second largest land bequest in the history of Sheriff’s Meadow.

A lifelong summer visitor to the Vineyard and a resident of Ardmore, Pa., who was the sister of the late Polly Hill, Mrs. Harris died in June of 2005 and her estate has finally now been settled.

Quansoo Farm embraces a globally rare coastal sandplain that fronts Black Point Pond on the western side of the Tisbury Great Pond overlooking the Atlantic Ocean. The property harbors a wide variety of rare plants and wildlife including wood lilies, ragged fringed orchids, goats rue, sandplain flax, short-eared owls and northern harriers. In the fall thousands of tree swallows hunt insects over the tawny grasslands studded with seaside goldenrod.

The property also includes a house that is believed to date to the 17th century and is one of a handful of houses remaining in the country that contains original wattle and daub construction. The future of the old Mitchell house at this writing is uncertain and preservation talks are under way.

But the future of Quansoo Farm is certain: the property will remain forever wild as a strategic piece in a cross-Island swath of sandplain grasslands that has been protected over the years, stretching from the Katama Air Park to the state forest to Sepiessa Point. “This helps conserve one of the largest and ecologically most important mosaics of grassland, heathland and other sandplain natural communities in the world,” said foundation executive director Dick Johnson in a statement about the gift this week.

Flipper Harris bought Quansoo Farm in 1970 and 1971, subject to a 30-year lease on the Mitchell farmhouse. The purchase was much to her family’s chagrin, she told friends years later. An individual in her own right and a woman of many unusual achievements for her era, Mrs. Harris was graduated from Vassar College in 1939 and later avidly pursued hobbies in ice dancing, sculpture and photography. She drove a Greyhound bus for a job while attending graduate school at Claremont College in California and in later years became interested in dowsing. And she grew up summering at Barnard’s Inn Farm in West Tisbury, today the world-renowned Polly Hill Arboretum. She went to Quansoo as a child and always had a special affection for the area.

“Flipper was a true visionary,” Mr. Johnson wrote in a Sheriff’s Meadow newsletter following her death two years ago. “Flipper had an artist’s sensibility and loved the farm’s spacious beauty. She told me that when it came up for sale, she just couldn’t stand the thought of houses being built all over the fields and woods.”

She bought the farm with the idea that she would find a way to preserve it, and over time, recoup her money.

And she did just that, through a series of charitable gifts of land beginning in 1979 with a conservation restriction donated to the town of Chilmark. Gifts to Sheriff’s Meadow followed in 1980, 1983, 1986, 1989 and 1993. The final gift of about 100 acres came through her estate following her death.

Mrs. Harris also had a great interest in preserving the Mitchell farmhouse and had planned to use money from her sister’s charitable remainder trust to restore the farmhouse for year-round use by an Island family. But when she learned that such a restoration would compromise the historical integrity of the house, she opted instead to build a separate farmhouse for Sheriff’s Meadow to house its executive director. She paid for the entire project herself, was actively involved in the design of the house and used her dowsing skills to help locate the well.

Her gift to Sheriff’s Meadow also includes an additional six-acre parcel of land that will be sold to establish an endowment to support Quansoo Farm, plus two Quansoo beach lots.

A portion of the farm is currently hayed by Elisha Smith, a well-known Island farmer. In the early years Mrs. Harris was interested in converting the farm to an organic vegetable operation, but the coastal climate and soil conditions proved unsuitable, and her plans for the land were adjusted accordingly. She had a long friendship and association with Larry Hepler, who beginning in the 1970s helped restore the land at Quansoo Farm by clearing away scrub oak that had grown up over the years. Mr. Hepler, who is a furniture maker and artisan, will remain in residence on the farm as property manager.

Sandplain grasslands, with their salt-blasted environment altered by natural fires, once covered extensive areas from Long Island to Nantucket, but over the last 300 years most of them have been lost to development. The Vineyard and Nantucket still harbor areas of sandplain grassland; the sandplains on the two Islands were named among the 40 Last Great Places on Earth in 1993 in a high-profile conservation initiative launched by The Nature Conservancy.

Due in part to the fact that Quansoo Road suffers from overuse, especially in the summer, there will be no public walking trails at the farm, although Sheriff’s Meadow will use the property for guided educational walks, including for school children, and for scientific projects. Preservation and restoration of the sandplain grassland will be ongoing.

Sheriff’s Meadow board members expressed gratitude this week for the Harris gift, which is second only to a gift of 158 acres from John and Nora Tuthill in Edgartown some years ago.

“It’s really extraordinary and just a wonderful example of a longtime relationship between Sheriff’s Meadow and a private landowner and being able to work with the landowner at her own speed and meet her goals,” said foundation vice president Emily Bramhall.

“I think that the most incredible, precious gift anybody can give to the Vineyard is to give land,” said Eleanor Graves, a member of the foundation board and its executive committee. She continued: “But having said that, I want to say that I think one of the really distinguished parts of this story and one of the most thrilling parts of it is the two sisters — that Polly gave Barnard’s Inn and [the arboretum] is now a worldwide treasure for everybody — and Flipper gave this property. What greater gift could the Vineyard have than this?”