Longwood Gardens has the most reported champion trees in the state of Pennsylvania. 63 Pennsylvania champion trees, that is the largest recorded specimens of a particular species or variety, grow at Longwood Gardens. The ranking of trees nominated for this recognition is based on three measurements: the height of the tree, the spread of the crown, and the circumference of the trunk. In Pennsylvania, a register of state champions is maintained by the Big Tree Committee of the Pennsylvania Forestry Association. Thus far about 500 champions have been recorded by this organization. All tree species, native or introduced, are eligible for nominations. The updated listing titled the "Big Trees of Pennsylvania" is published periodically and is also available on-line at www.pabigtrees.com. One of Longwood's champion trees has been recognized in the National Register of Big Trees coordinated by the American Forests magazine. This national listing, available on-line at www.americanforests.org, records the largest specimens of more than 730 species, but is limited to those trees that are either native or naturalized in the United States.