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Pterocarya fraxinifolia

Pterocarya fraxinifolia - Caucasian wingnut

The wingnuts (Pterocarya) are large deciduous monoecious trees (i.e. male and female flowers in the same tree) whose dangling inflorescences develop into fruit catkins up to half a metre long. The name comes from the decorative winged nuts. This particular species, the Caucasian wingnut, has grown in earlier periods of warmer climate in Europe but has had to retreat to its present habitat in the river valleys around the Caspian Sea. It was taken into cultivation in western Europe at the end of the 1700s.

This is the handsomest of the wingnuts which can be grown successfully in Finland, with large compound leaves of opposite leaflets. Unfortunately the provenance of the seed cultivated in nurseries is hopelessly tender in Finnish winters. Plants from Uppsala have grown to over 20 metres in the Djurbäck Arboretum in Inkoo, southern Finland, in only a few decades. It seems that to thrive, seed must be of suitable provenance and the soil rich and moist, with protection from late spring frosts.

The Caucasian wingnut closely resembles the Japanese. A good way to distinguish between the two is the scales protecting the buds: in the Caucasian they are completely absent; in the Japanese they fall during the winter.

 

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