When we think of Japan, we often think of cherry blossoms and maples. However, about 5,600 species of vascular plants flourish in Japan. This species diversity is due to the country's varied climate zones. Within the string of more than 3,000 islands called the Japanese archipelago, subtropical, temperate, and alpine-arctic zones exist, providing habitat for many species. The islands of Japan correspond in latitude to the Atlantic states of Maine and northern Florida, exhibiting nearly the same kind of climatic range. Our collection contains plants native to the main islands of Japan: Hokkaido, Honshu, Shikoku, and Kyushu. Beginning in 1978, and continuing today, additions to this collection reflect an emphasis by the Arboretum on acquiring wild-collected genetic material.
Located within the floodplain of the DuPage River, the Arboretum’s Japan collection has long suffered from seasonal flooding and excessive spring wetness, creating challenging growing conditions for those plant species not tolerant of standing water or a saturated soil. In 2016, the Japan Collection was extended southwards across the main road into the former Plants of Acid Soils collection. This expanded collection now allows use of varied landscape features, including a slope, to provide better growing conditions for many plant species native to Japan. Several of the specimens from the Japan collection that were displaced or otherwise impacted by the DuPage River Restoration have already been transplanted to the new site where they are establishing in the landscape.
The Arboretum's Japan Collection includes maples, cherries and pears, among them the Ussurian pear (Pyrus ussuriensis). This species was one of the first specimens to be planted in 1922. It was originally collected in Japan by Ernest H. Wilson, a renowned plant collector. Today the tree is 20-feet high and 40-feet wide. It is always the center of attention in spring, when it is completely covered with pure white blossoms.
Another notable species is the katsura tree (Cercidiphyllum japonicum). This species is one of the largest hardwoods in Asia, and can reach heights of 130-150 feet (40-45 meters) and trunk diameters of 7 feet (2 meters). The leaves are heart-shaped (similar to leaves of the native redbud (Cercis canadensis), but arranged opposite instead of alternate). In autumn, the leaves of the katsura tree turn a muted yellow and release the pleasant scent of burnt sugar or cotton candy.