In addition to designing the formal Rose Garden in 1899, Spencer and Katrina Trask also created a more informal woodland Rock Garden between the house and the Rose Garden. The Trask’s design process for the Rock Garden is even less well-documented than the Rose Garden. The Rock Garden has also not received the same level of attention in the writings or art produced on Yaddo as the formal garden. The Trasks likely found their inspiration for the Rock Garden in Japanese gardens, which became popular in America during the early-twentieth century. Since the Trasks were keenly aware of design trends in the decorative arts, they probably wanted to have a garden on the cutting edge of American landscape architecture. While the Rose Garden was to be a riff on a classic, the Rock Garden was an avant-garde expression of a novel landscape form.
Like the Rose Garden, the Rock Garden was a unique creation of the Trasks’ that reflected the stylistic influence of Japanese gardens but was not a faithful copy of the landscape form. The Trasks located the Rock Garden in a grove of white pine trees. They made the garden’s focal point a circular mound of stones with a jet of water spurting from the top of the pile into a pool of water surrounding the base. The pool contained multicolored water lilies. Water from this pool ran downhill through a manmade stream bed to a smaller pond with a classical fountain consisting of a nymph astride a fish. Japanese irises surrounded the smaller pond, which was also filled with water lillies. Since Yaddo does not have natural stone outcroppings, Spencer acquired the stones lining the stream and ponds from a quarry. He intentionally selected rugged and irregularly shaped rocks for their visual interest. The Trasks planted the gardens surrounding the water features with a mixture of annuals and perennials intended to bloom from the spring through the fall, sharply contrasting the bright flowers and the gray stone. The garden had natural rock seats and stone Japanese lanterns.
Spencer installed a classical gateway next to the greenhouse between the gardens and the house. Known as the Memorial Gate, Spencer designed and presented the gateway to Katrina as a gift during the fall of 1899. The Memorial Gate served as a clairvoyee, or a frame through which the vista of the gardens could be enjoyed from the house. Now, the Memorial Gate demarcates the boundary between the private space at Yaddo and the public gardens.