San Diego's Balboa Park is spread out over 1,200 acres making it the largest urban park in the country. It's also one of the oldest having been created in 1868. Balboa Park has 16 gardens, a Botanical Building, and many other plants throughout its grounds.
The Cedar Valley Arboretum is 35 acres in size and has different areas with different themes. These include a Rose Garden, Mosaiculture Garden, Children's Gardens, Butterfly Conservation Meadow, and Master Gardeners Orchard. The arboretum is at Waterloo, Iowa.
University of California, Irvine has 24,000 trees in its campus. At the center of the campus is Aldrich Park which in its 19 acres has 11,050 trees and shrubs. There is also a rose garden and other areas with flowers.
The Desert Garden is 2.5 acres in size and contains more than 1,300 plants which include succulents and drought-resistant plants from around the world. It is one of the gardens in Balboa Park which is located in San Diego, California.