The original Barnes Foundation campus in Merion, Pennsylvania, is now a 12-acre arboretum open to the public for tours. The plant collection features favorite plants assembled by Mrs. Barnes for teaching purposes, and includes stewartia, aesculus, phellodendron, clethra, magnolia, viburnums, lilacs, roses, peonies, hostas, medicinal plants, and hardy ferns.[46] A herbarium and horticulture library is available to the Foundation's horticulture students and other scholars by appointment.