The original library building — designed by architect Edward Larrabee Barnes — was completed in the spring of 1981 and was used to consolidate Bunny Mellon’s considerable collection in one location. The library was expanded with an additional wing — designed by local architect Thomas Beach — which was completed in the winter of 1997.

"This collection of books and drawings grew as a way of life, not just a gathering of rare and interesting books bought at the enticement of an enthusiastic bookseller, but chosen one by one for their special and unusual contents and design, as well as their relationship to books already part of the collection." - Bunny Mellon

"It is a working library where mystery, fascination, and romance contribute to centuries of the art of gardening as a source of discovery." - Bunny Mellon

The library is a thriving research center housing 16,000 objects, including: modern and rare books; manuscripts; drawings; prints; sculpture; collections of which are being digitized for public online access.

The building has work spaces for traveling scholars to use the collections and discuss their work.

Nearly one-tenth of the library's printed materials collection is made up of rare books dating between 1499-1900. 

"These books about the outdoors live not in dusty darkness, but behind simple, pale oak doors, easily opened to the world they tell about." - Bunny Mellon

"A library is built during a lifetime, it doesn’t happen overnight.” - Bunny Mellon