Sun Garden (Quad City Botanical Center)

The project began in the late 1990s, when five founding members set out to build a greenhouse in Rock Island. After weighing the options they settled on a botanical centre focused on education, toured other gardens and met with architects. Construction, carried out for the Quad City Botanical Association, was completed in spring 1998, and the centre opened on 20 June that year, welcoming visitors straight into its tropical atrium, the Sun Garden, which has since won awards.

The site then grew around the glasshouse. A collection of rare conifers, raised by Chub Harper on his own land and later donated, was established in 2001. In 2003 came a garden of beds at varying heights, designed for gardeners with physical limitations and maintained by them. The children's garden, a playful take on the Mississippi, has gained a new area representing the river's source at Lake Itasca. In 2024 the centre launched a Plant Discovery Bus that takes its education programmes to local students.

The Sun Garden is a climate-controlled atrium of 6,444 square feet (about 600 m²) rising to a skylight 70 feet (about 21 m) high. Its steel frame had to cope with a harsh environment of warmth, high humidity and ultraviolet light pouring through the extensive glazing. The steel members were blast-cleaned and shop-primed with a zinc-rich coating; after erection they received an epoxy intermediate coat on site and a neutral grey acrylic polyurethane finish that resists abrasion and UV. The project data sheet names Chanoe Environmental of Cedar Rapids, Iowa, as engineer.

The tropical climate depends on water. A 14-foot (about 4 m) waterfall, a stream and a pond circulate water through the atrium and supply the humidity the plants need, helped by a fogging system in several display areas. A glass wall divides the indoor koi pond from an outdoor goldfish pond, so that the two pools mirror each other on either side of the glazing. A working greenhouse next door serves as plant store, potting room and classroom.

The Sun Garden holds hundreds of tropical plants, with an emphasis on useful and fruiting species: coconut, banana, vanilla, coffee and cacao, along with cardamom, cassava, lychee, papaya, pineapple, sapodilla, allspice and ylang-ylang. Palms, ferns, bromeliads, orchids, frangipani, Arabian jasmine, bird of paradise, bamboo and papyrus fill out the planting, and the Japanese koi in the pond are among the most popular residents.

The adjoining working greenhouse, whose contents are always changing, houses the cactus collection, which includes plants from founding member Al Dieter, as well as orchids, hoyas and succulents. It also takes in tropical plants during the colder months and is where stock is prepared for the public plant sales.

The centre stands at 2525 4th Avenue in Rock Island, close to the Mississippi. Allow one to two hours for the atrium and the outdoor gardens: a children's garden inspired by the river, the rare conifer collection, a wildflower prairie evoking the grassland that once covered Illinois and a butterfly garden around a pergola. From May to October a 1:24 scale garden railway, with nearly 800 feet (about 240 m) of track, runs on weekend afternoons in an adjoining garden reached from inside the centre. The heated atrium offers a tropical stop in any season, the depths of winter included.