This poster documents a collaborative project that Joseph Beuys staged in Documenta 7, a large exhibition of contemporary art that takes place every five years in Kassel, Germany. Focusing on green urban renewal, the idea was to plant 7000 oak trees (in German, eichen) with the help of volunteers throughout the city. The trees were paired with 7000 column-shaped pieces of basalt rock, piled outside of Museum Fridericianum in the city centre. Every time money was raised to plant a tree, one of the basalt columns would be removed and set up next to the tree. This artistic, ecological and social intervention was intended as only the beginning of a global mission for environmental and social change.