Four 6-cent stamps saluting the XI International Botanical Congress were placed on sale at Seattle, Washington, on August 23, 1969. A printing of 120 million stamps in panes of fifty was authorized.
Designs of the four stamps are representative of flora from the four corners of the country. The Southwest is represented by the ocotillo; the Northwest by the Douglas fir; the Northeast by the lady-slipper, and the Southeast by the franklinia.
These stamps, designed by Stanley Galli of Kentfield, California, were printed on a sheet similar to the beautification series. Two offset press passes applied yellow, red, blue, and green inks. One Giori pass added black, orange, and pink.
Postal Bulletin (July 31, 1969).