Mrs. Thompson’s Conservatory

By Laurel C. Wemett

When Mary Clark Thompson died in 1923 she left an impressive legacy. She was a notable philanthropist, but is perhaps best known today in the Finger Lakes and beyond for Sonnenberg Gardens, the summer home in Canandaigua that she created with her husband Frederick Ferris Thompson, a New York City banker. When Sonnenberg opens for the season in May, one of the estate’s key historic features, the Palm House, the central domed conservatory, will reopen after having undergone a major restoration.  

From Private Residence to State Park
The Thompsons, whose principal residence was in New York City, purchased a 300- acre farmstead in Canandaigua in 1863, calling it Sonnenberg (German for “sunny hill”). The couple replaced an original farmstead residence with a 40-room, Queen-Anne-style mansion in 1887.  The Sonnenberg website states that when Mr. Thompson died in 1899, Mrs. Thompson began “re-designing, renovating, and building the diverse gardens surrounding the mansion as a living memorial to her husband.”
Her additions to the Canandaigua property included nine gardens, aviaries, and the 13,000-square-foot greenhouse complex, including the striking Palm House. It was built between 1903 and 1915 by Lord & Burnham of New York City.
In the nearly 100 years since Mrs. Thompson’s death, the Sonnenberg estate has changed hands several times. It passed first to her nephew, who sold it in 1931 to the federal government. The Veterans Administration built a hospital complex there. In 1972, the property was transferred to a not-for-profit organization whose aim was to purchase, preserve and restore a 50-acre portion of the original estate and gardens, including the mansion and greenhouse complex. It has been open to the public for more than 40 years.    

In 2006, Sonnenberg Gardens and Mansion became a State Historic Park owned by New York State’s Office of Parks, Recreation and Historic Preservation. The arrangement brought stability to the estate, which welcomed more than 35,000 visitors in 2016.  However, funding for operation and maintenance does not come from the state park system. “Opening the gates, planting the gardens, opening the historic house museum, and maintaining and improving the site to secure its future” falls to the community nonprofit, explains Sonnenberg’s Executive Director David Hutchings. A small staff and a large cadre of seasonal volunteers generate revenue largely from memberships and donations, special events, grants, and rentals.  

Restoring the Lord & Burnham Conservatory
Sonnenberg’s greenhouse complex is one of the few remaining and intact Lord & Burnham greenhouses in the United States. The company, founded in Buffalo in 1849, built major public and private conservatories. Surviving Lord & Burnham conservatories from Mrs. Thompson’s period are at the New York Botanical Garden in the Bronx and the Buffalo & Erie County Botanical Gardens.
“A conservatory was a way of showing great wealth,” explains David Hutchings, who serves as Sonnenberg’s lead Horticulturalist directing all design, growing and installation of the historic public gardens. The 19th century is described as the golden age of conservatory building. Industrial advances and the love of gardening produced an interest in exotic gardens under glass, across all levels of society. Affluent homeowners began adding greenhouses to their estates to provide fresh flowers and fruits.
In their 2009 Historic Structure Report on the 1903 conservatory complex, Syracuse architects and preservation planners Crawford & Stearns described the Conservatory Complex of greenhouses at Sonnenberg as “one of the most dramatic and impressive groupings of structures at the site.” Their report recommended continuous ongoing repair and maintenance.
It was last worked on 30 years ago.

The “Crown Jewel”
“We are a small not-for-profit but have really big ideas,” says Barbara Stahl, a volunteer and member of the Board of Trustees who serves as Sonnenberg’s historian and archivist. “We are constantly working on visions, plans, and how to accomplish them,” says the retired library media specialist whose research has resulted in her writing several publications about Sonnenberg’s history.   
“We are being pragmatic to insure that the Palm House will last another 100 years,” says Hutchings of its restoration. The domed structure, which measures 39 feet tall and 52 feet long is sometimes referred to as the “crown jewel” of the greenhouse complex.    
“The conservatory was one of the first things Mrs. Thompson finished,” adds Hutchings, who points out that the tropical plants growing in the Palm House include an original banana tree and Bird of Paradise plant that delight visitors today. “My dream is to see the entire greenhouse complex be returned to what it was in Mrs. Thompson’s time.”  
All of the original complex still stands today except the Vegetable Pit and Violet Pit, which were both demolished in 1959.  Other sections included the Chrysanthemum House, Peach and Nectarine House, Orchid House, Grapery, Mushroom Cellar, Melon Houses, Rose House, Carnation House, Propagation House and two display houses. Stahl explains that fruits, vegetables and flowers from the Canandaigua estate were enjoyed by Mrs. Thompson when she was at her permanent residence on Madison Avenue in New York City. “Her employees routinely sent these items to her via the railroad. In addition, such produce was also furnished to the F.F. Thompson Memorial Hospital and the Clark Manor House, a home for the elderly. Both establishments were philanthropic gifts to Canandaigua from Mrs. Thompson.”  
Renovation in 2016, under the direction of architect Paul Minor and historic preservation consultant Peter Trieb of Lima, was made possible by a matching grant received as part of the Finger Lakes Regional Economic Development Council’s grant through the State of New York.   Grants from the Rochester Area Community Foundation and the Davenport-Hatch Foundation provided much needed additional support, along with a donation from the Canandaigua Chapter of the Daughters of the American Revolution (DAR), and numerous individual contributions.   Mary Clark Thompson was a member of the DAR, a women’s service organization founded in 1890 to promote patriotism, preserve American history and support better education for our nation’s children.     
Stepping Up to the Challenge
After the job went to bid, it was awarded to local contractor Sandman’s Sandblasting and Coatings. Based in nearby Manchester, the business is owned by Richard Deys, who employs 15 full-time workers, all of whom are OSHA and lead-paint certified, as well as certified for preservation work. Sandman’s had previously helped Sonnenberg Gardens to get small historical pieces like swings and benches “back in shape.” Restoration work on the Palm House began in June 2016 and the business donated $100,000 worth of labor to the project.       
“Sandman’s main work is with municipalities – sandblasting highway trucks, repainting them, and welding,” explains Richard Deys, who graduated high school as a nuclear-certified welder. Sandman’s projects are varied and sometimes very large, reflecting Deys’ love of a challenge. Their preservation work is carried out on everything from navy ships to major military aircraft, as seen at Many of the locomotives for the Finger Lakes Railroad are painted by Sandman’s.  
In 2017 they will carry out work on steam engines at the Railroad Museum of Pennsylvania in Strasburg, Lancaster County. They even painted metal sculptures created by renowned sculptor Albert Paley, including many of the thirteen installed for exhibition on Park Avenue in New York City in 2013.    

1,200 Pieces of Glass
Deys’ son Jacob, a June 2016 graduate of Gananda High school, served as head foreman for this job. “Jacob took out over 1,200 pieces of glass in the dome; then everything was labeled to put back in the same spot,” said Richard. Each piece of glass was cleaned and painted, and since each is different and has to be squared up to the structure one piece at a time, all the work was done onsite. “Jacob takes it extremely seriously,” says his father. “He’s been in my coat pocket and knows the trade. This work takes a certain type of person.”
Early greenhouses such as Sonnenberg’s were made of cypress wood and iron or steel.  Many wooden sashes, sills and doors were either replaced or restored. Structural ribs, purlins, and posts (the infrastructure of the dome) required minor repairs. Hand-hewn wooden ribs made out of cedar wood were replicated as needed.    
After the glass panes were painstakingly returned to their original locations, a UV resistant paint was applied to the inside of the panes to further reduce the ultraviolet rays of the sun. This coating helps to control the environment, regulating the extremes of temperatures. By November 2016, 80 percent of the work had been completed with only minor repairs and cleanup remaining.       
“Most greenhouses didn’t last 100 years; they are long gone,” says Deys. “Our big job is to bring the conservatory complex back.”
The challenge is to make it as close to the original as possible. Over the years, the greenhouse has been repaired and changed. Sandman’s was guided by copies of the Lord & Burnham blueprints and a few available photographs. “With the tools we have today it is simple for us to repair; they had to start from scratch,” said Deys.
“The public should know about the conservatory and Palm House,” he adds. “The best thing to do is to visit Sonnenberg and see it with your own eyes.”    
As funds for continued restoration are received, more of the greenhouses can be opened again and returned to their original utilitarian uses. Donations to the greenhouse complex can be made online or directed to the Greenhouse Fund c/o Sonnenberg Gardens and Mansion. Contact David Hutchings at with any questions.

1 Comment

  • mtman2 says:

    I lived in Clarks Reservation State Park to later to pay my way thru Environmental studies at FLCC worked in the original crew that began the restoration of Sonnenburg Gardens Estate for Ontario County…!
    Now learn Mary CLARK Thompson bought that Park land & named after her…!

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