Installed atop a parking garage and enclosed by buildings, this square (200 x 200 feet) courtyard plaza is heavily used by students of the University of Minnesota Twin Cities campus. Named for David M. Lilly, former member of the Federal Reserve Board and Vice President of Finance and Operations for the university, the plaza was designed by Oehme, van Sweden & Associates in the 1990s. The cold-hardy, drought-tolerant plant palette responds to the site challenges associated with rooftop plantings in northern climates.
Extending the circulation pattern of the larger campus, crisscrossing walks divide the plaza into quadrants. The plantings of these quadrants, each differing in composition and structure, contrast with the uniform lawns found in nearby courtyards. Blends of perennials, grasses, and shrubs fill the south and east quadrants while flowering drifts form a rich and textured ground plane. A small bosque of honey locust occupies the north quadrant, providing dappled shade for seating, while manicured lawn fills the west section. Multi-functional retaining walls address the grade change, serve as seating walls, and enclose the densely planted areas. A small amphitheater and eight planter boxes located in the central paved hardscaped square also provides seating. A walkway bisecting the southern quadrant contains a semi-circular seating wall facing a fountain in which water cascades down a stepped runnel. The cast-concrete hardscape did not weather Minnesota’s harsh conditions as well as the plants and, in 2013, the walkways were replaced with an improved blend of concrete and granite-chip aggregate. This rehabilitation project also removed a serpentine pathway that formerly bisected the lawn area.