The Quad City Botanical Center in Rock Island, Illinois, opened in 1998 as a public garden complex beside the Mississippi River. Its centerpiece is the Sun Garden conservatory, a tropical indoor space with a large skylight, waterfall, reflecting pools, and plants including cacao, coffee, coconut, banana, papaya, orchids, palms, and vanilla. The site also includes specialized outdoor gardens, among them a conifer garden based on Justin C. Harper’s collection, an accessible garden with beds at varying heights, and a children’s garden. In 2024, it added a mobile Plant Discovery Bus, strengthening its role as both a display garden and an educational resource for the Quad Cities.