National Arbor Day, founded by Julius Sterling Morton, is a nationwide observance encouraging tree planting in the U.S.. The federally designated date occurs the last Friday in April, but many states observe Arbor Day on dates better suited to their best tree-planting times.

The following states observe Arbor Day on National Arbor Day, the last Friday in April: Arizona, Connecticut, Delaware, District of Columbia, Idaho, Illinois, Indiana, Iowa, Kansas, Massachusetts, Michigan, Minnesota, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, South Dakota, Texas, Utah’, Wisconsin.