A mix of stone, concrete and greenery reflects the center's philosophy of urban horticulture.. In Short The horticulture center has greenhouses, gardens, meeting halls, a Master Gardeners office and a library that is open to the public and quite popular with local gardeners. The center hosts plant sales, seminars and weekly gardening clinics. Horticulture students and staff also manage the plant collection at the nearby Washington Park Arboretum. The center was the first and is the largest program in the world devoted to studying plants in cities.