It seems that the only external characteristic differentiating the Japanese from the Manchurian ash is the greater hairiness of the leaf undersides. Being from a maritime climate it is probably better suited to the fluctuations of the Suomi climate than the Manchurian form. However, because it tends to break leaf very early, it is best planted in cool, permanently moist sites under a protective tree canopy. Resembling the native ash (F. excelsior), the Japanese ash flowers early before leaf flush, the flowers themselves being easy to miss. The typical ash keys develop in bunches on female trees, persisting into late autumn.