Though notable features from this period are the Rose Arbor, the Circular Pool and the Green Garden Court, Coe recalled in later life, "Mrs Byrne had done very little in the shape of landscaping.

Massive purchases of rhododendrons were made in England, Japanese crabapples and cherries, and forest and specimen trees, lindens, Scotch and red pines, oaks.

The property's first mansion burned to the ground on March 19, 1918; its replacement, the present Coe Hall, was constructed between 1918 and 1921 in the Tudor Revival style and faced in Indiana limestone.

Sargent in 1918, the Coes appointed the Olmsted Brothers of Brookline, Massachusetts, with James Frederick Dawson as chief landscape architect, who brought their signature "naturalistic" look to the north side of the property.

It was James F. Dawson's idea to sink the tubs directly in the ground, rather than trundle them out seasonally, the usual procedure for camellias grown in greenhouses.

Today, the Main Greenhouse offers large collections of orchids, cacti and succulents, houseplants, ferns and begonias, as well as seasonal displays of chrysanthemum, poinsettia, hydrangea, coleus, etc.

The nearby full-scale conifers can reach over 60 feet (18 m) tall, and include sequoia, metasequoia, larch, fir, spruce and pine, with a large assortment of Rhododendron species under the canopy.

[4] During an interim period between 1955 and 1964, in addition to its role as Planting Fields Arboretum, a park, the land was used as a temporary campus for a State University of New York (SUNY) college of science and engineering, which was known as the State University College On Long Island at Oyster Bay (SUCOLI) while donated land in Stony Brook, NY was being developed into the new permanent campus.

At first all activities were located inside Coe Hall, but as the college grew, dormitories were moved to the stables and temporary dome structures were erected on the grounds for classes and laboratories.

Subsequent to Stony Brook University moving to its permanent campus in Suffolk County, the site became home to another SUNY endeavor, the Center for International Studies and World Affairs ("ISWA").

Today it is owned and operated by New York State Office of Parks, Recreation, and Historic Preservation in cooperation with Planting Fields Foundation, with its world-renowned arboretum and the Coe Hall mansion, is a popular attraction.

[clarify] Therefore, Oyster Bay Post Office which serves this area of Upper Brookville is displayed as the official USPS mailing address.