Her projects varied widely in composition and plant material and demonstrated a comprehensive knowledge of English, French, Dutch, Indian, Italian, Turkish and Japanese design.

[6] Her plans were created for friends and clients as notable as New York architect, historian and social reformer Isaac Newton Phelps Stokes, author of the monumental series The Iconography of Manhattan Island; the families of financiers William Avery Rockefeller and William Goodsell Rockefeller of Greenwich, Connecticut; Remington Arms President Samuel F. Pryor; and yachtsmen C. Oliver Iselin and Henry R.

[7][8] By 1926, she was one of the few women who leased office space in the Architects Building at 101 Park Avenue in Manhattan (the others being Marian Cruger Coffin and Ruth Dean), [9] and her portfolio of projects ranged as far south as Palm Beach, Florida and as far north as Manchester-by-the-Sea, Massachusetts.

Jay's original mission was to supervise an agricultural unit to help residents of villages like Soissons in Aisne recover from the destruction of the Great War,[12] but because of hostile activity in the area she was sent to Versailles instead to work with wounded and shell-shocked soldiers in the Garden Army Service.

With an evident passion for culture and history, her talks highlighted what had been lost in foreign countries during wartime but also emphasized the resilience of landscapes and the potential for what could be restored through design.

Her collection of slides was donated posthumously to her distant cousin and fellow landscape architect Beatrix Jones Farrand and the Reef Point Library in Maine.