Ruppert Nurseries Fall color in the fields—young scarlet oaks and Donald Wyman crabapples. The nursery is experimenting with training different species, like these river birches, into espalier. Espaliered trident maples against a sunny wall at the nursery office. Regal Prince oaks trained into an arch at the parking area. Sharon spent a beautiful morning tagging trees at Ruppert Nurseries in Laytonsville, MD.