[1] New rose cultivars are continually sent to the garden from many parts of the world and are evaluated on several characteristics, including disease resistance, bloom formation, color, and fragrance.

The Park Bureau approved the idea in 1917 and by early 1918, hybridists from England began to send roses.

[3] A decade before the test garden was proposed, 20 miles (32 km) of Portland's streets had been lined with rose bushes for the 1905 Lewis and Clark Centennial Exposition.

[1] In early 1918, the garden began receiving plants from growers in England and Ireland, as well as Los Angeles, Washington and the Eastern United States.

[1] In 1921 Florence Holmes Gerke, the landscape architect for the city of Portland, was charged with designing the International Rose Test Garden and the amphitheatre.

The Frank E. Beach Memorial Fountain (officially titled Water Sculpture) is an abstract stainless steel sculpture and fountain along the main promenade, designed and built by Oregon artist Lee Kelly and dedicated in 1975.

The roses testing in the garden are identified by number rather than by name; the plants are evaluated for two years by multiple criteria before being judged.

[3][4] The garden features a gazebo added in 1991, and a wall honoring past presidents of the Portland Rose Society.

The Royal Rosarian Garden displays roses honoring past Prime Ministers of the Royal Rosarians, a civic group which serves as the official greeters and goodwill ambassadors for the City of Portland who serve in the many Rose Festival events, and features a stone bench honoring Jesse Currey.

[10] The national annual American Rose Society winners are displayed in the middle of the garden along the center aisle.

[11] The rose garden is served by TriMet bus route 63-Washington Park, which runs seven days a week.

[12] Washington Park Shuttle, a free service which connects the Rose Garden to MAX light rail at the Washington Park station, operates seven days a week from April through October, and only on weekends from November through March.