Dia installed five basalt stone columns, each paired with a tree, at 548 West 22nd Street in 1988, continuing the sculpture project 7000 Eichen (7000 Oaks) by German artist Joseph Beuys. Five different varieties of trees were planted: gingko, linden, bradford pear, sycamore, and oak. In 1996 Dia extended this project by planting 18 new trees, each paired with a basalt stone, on 22nd Street from 10th to 11th avenues, adding Pin Oak, Red Oak, Elm Honey Locust, Gingko, and Linden.
Beuys’s project 7000 Oaks was begun in 1982 at Documenta 7, the large international art exhibition in Kassel, Germany. His plan called for the planting of 7,000 trees, each paired with a columnar basalt stone approximately four feet high above ground, throughout the greater city of Kassel. With major support from Dia Art Foundation, the project was carried forward under the auspices of the Free International University (FIU) and took five years to complete, the last tree having been planted at the opening of Documenta 8 in 1987. Beuys intended the Kassel project to be the first stage in an ongoing scheme of tree planting to be extended throughout the world as part of a global mission to effect environmental and social change; locally, the action was a gesture towards urban renewal.