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17 Feb 2023

Plant of the month: Pterocarya fraxinifolia

Written by Lucrezia Rossi, PLANTS Inventory Officer
Pterocarya fraxinifolia at Threave Garden
The PLANTS team blog continues with a look at the beautiful Caucasian wingnut (Pterocarya fraxinifolia).

Pterocarya fraxinifolia, commonly known as the Caucasian wingnut, is a medium-sized deciduous tree in the Juglandaceae family, which includes other nut-producing trees such as walnuts and hickories.

Pterocarya fraxinifolia is native to the Caucasus region of Eurasia – from northern Iran to Ukraine – where it usually grows on sites near open water, such as river valleys. It gets its interesting name from its fruit: after spring flowering, small green winged nutlets develop in the female catkins in early summer, forming pendulous strings that can reach 50cm in length.

The genus name (Pterocarya) comes from the Greek words pteron (wing) and karyon (nut); indeed, Karya is the old Greek name for the walnut tree, whereas the species name (fraxinifolia) refers to the similarity of the leaf to that of some ashes (Fraxinus being the ash genus and folia meaning leaf). The nuts of Pterocarya fraxinifolia are often referred to as ‘flying saucers’ because of their wings, which aid dispersal by wind.

This tree is mostly used as an ornamental plant in parks and urban gardens, and it is easy to see why. When I first encountered Pterocarya fraxinifolia at Threave Garden, where I was doing an inventory work as part of the PLANTS project, I was immediately stunned by its beauty. It was towards the end of September during a very rainy and windy day, and while on my way back to the office I remember seeing the catkins of this plant dangling in the wind, giving it a wonderful and magical appearance.

Apart from being such a handsome plant, the Pterocarya has been found to have other extraordinary qualities. For instance, extracts from this tree are used to dye nylon as a replacement to synthetic dyes, which are toxic to the environment. Moreover, recent research has shown that leaf and bark extracts of Pterocarya fraxinifolia have good levels of antioxidant activity which may introduce its leaf as a useful medicinal plant.

The nuts are edible and often used in cooking thanks to their sweet taste. They are known to be rich in oils and proteins, conferring them important beneficial properties: they are in fact good for the heart as they can lower cholesterol levels. The tree is also a great food source for wildlife, from small insects to larger mammals.

Overall, Pterocarya fraxinifolia is a beautiful and versatile tree that is well-suited for both ornamental and practical use. Its large, compound leaves and winged nuts make it a unique and interesting addition to any landscape, and for anyone who should fall in love with this plant, it can also be grown as a bonsai, producing beautiful miniature wingnuts!

Plant Listing at the National Trust for Scotland (PLANTS) is the biggest horticultural audit project undertaken by the Trust and aims to celebrate, protect and better understand the flora and vegetation across our gardens and designed landscapes.

Read more about the PLANTS project

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