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Fraxinus mandshurica

Fraxinus mandshurica var. mandshurica

The Manchurian ash resembles the native Finnish species, the European ash (F. excelsior), but its leaves are considerably larger and the shoots thicker; as if painted with a broader brush. The previous year’s shoots are bluntly angular. The wind-pollinated flowers appear before leaf flush and are polygamous, i.e. each tree can have flowers with male and female organs, or flowers which are only male or female, or any combination of any or all of these.

The large leaves are very similar to those of the North American black ash (F. nigra) and some botanists consider these two to be related subspecies. In the wild Manchurian ash grows in sparse mountain slope forests and open river valley groves in East Asia. It is naturally adapted to a continental climate, which makes it frost-hardier than Finland’s native ash, but at the same time much more susceptible to late spring frosts. This means that in Finland it is best suited to sheltered sites in eastern parts of the country.


Fraxinus mandshurica var. japonica - Japanese, or Manchurian ash

The Japanese ash is a form of Manchurian ash growing naturally on the northern Japanese islands of Honshu and Hokkaido, as well as on Sakhalin Island. On the cool mountain slopes it tends to concentrate in moist sites at the edges of mires or along rivers, with conifer forest dominating drier sites. Highly valued for the attractive patterning of its timber, the Japanese ash has become rather rare in the wild because of over-exploitation.

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 Finnish 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.


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