The island nation of Japan has very rich and diverse flora. Its southernmost islands are situated near the tropics where the plants are unsuitable for the Finnish climate. Plants from the northern islands of Hokkaido and Honshu, however, do thrive in Finland. A separate section was therefore created within the Niskala arboretum to present a broad selection of these Japanese species.
Japanese trees and shrubs are typical of a humid oceanic climate with relative small annual and diurnal variations in temperature. The ocean stores heat like a radiator. It warms up in the spring slowly and gradually cools down in the fall. As a result, plants start to grow late in the spring and are not exposed to frosts. However, they may be exposed to frosts in autumn, as they prepare late for winter. In severe winters they can be damaged badly.
The cultivation of Japanese plants in Finland began in the late 1800s, when collectors would import the rare seedlings from European plant nurseries. Since Japan was cut off from the rest of the world for such a long time, the scientific documentation of its flora began quite late.