Cercidiphyllum

The large-leaf katsura grows naturally only in the central mountains of Honshu, Japan’s main island. The leaves are bronze-coloured when they open, bigger than those of the small-leaf katsura (C. japonicum), with a heart-shaped base. In autumn they turn wonderful shades of pink, violet and yellow and fill the air with the scent of burnt sugar when they fall.

In Finland this species has done well on the south coast, where it develops into a small, slender-branched tree. When young, the crown is conical but takes on a rounder shape with age. It needs a rich, light acidic soil which retains some moisture, and the protection of other trees from spring frosts.

At Mustila, there is a single individual tree growing at the west end of Etelärinne (Southern Slope), and some younger plantings along the stream in Tuijalaakso (White Cedar Valley). Seeds were received at Mustila in 2003 from the Komarov Institute in St. Petersburg and in 2008 from Milde Arboretum in Bergen, Norway. The excellent trees at Milde were grown from seed collected at about 2000m asl in the Japanese mountains by the combined Scandinavian collecting expedition of 1976. The resulting plants seem to be thriving in Finland, too.

The katsura is an important forest production tree in its native Japan, where it can reach 30m. In Europe it is smaller, remaining a small tree or a shrub. The leaves are almost round with scalloped edges, and regularly positioned along the branches. This gives the tree a uniquely beautiful habit which has made it one of the most valued for landscaping, though it has neither showy flowers nor fruit. In autumn the leaves turn shades from white to a variety of reds, though yellow is perhaps most prevalent. After falling, they emit a sweet scent which has been compared with gingerbread, burnt sugar and vanilla.

Katsuras, though rare in Finland, have been grown here for decades. They are often of indeterminate provenance grown in central European nurseries, and can be frost-damaged in cold winters even in the south of Finland. However, a hardy natural provenance grown at Gothenburg Botanical Garden has thrived as far north as Oulu, so it appears that seed gathered in cold areas is noticeably hardier, and would provide useful landscaping trees for south and central Finland.

Katsura is a demanding tree of rich forests, so for successful growing requires deep soil which does not freeze and should never become dry during summer. It survives on drier soils, but remains shrubby. It is less demanding about light, tolerating light shade. In the protection of other trees or of buildings its leaves, which break early in the spring, are better protected from spring frosts.