This tree can take a few years to get established but it has a trick up its sleeve to help: its leaves produce a natural herbicide that washes off into the soil around it, and prevents other trees growing nearby.
Chinese walnut (Juglans cathayensis) at Kew Gardens
About Kew's Chinese walnut trees
Kew's specimens of this tree are small for their type because, although they are hardy, our local weather patterns do not fit their growth habits well. Subjected to frosts at certain times of year, the trees can lose their 'leader' - the shoot leading the upward growth - and hence they often stay short and stocky.
Take a closer look
- The leaves of this tree grow up to almost a metre in length. Each has 11 - 19 smaller leaflets arranged in pairs along a central stalk.
- Some members of the walnut family have nuts that grow within an outer husk - technically making them 'drupes' rather than true nuts - developing from the same plant parts as peaches or olives.
- Look for long catkins – some up to 40 cm – in spring. These are the male flowers, with female flowers in spikes at the end. From August, these begin to ripen into tough and thick-shelled nuts.
The Chinese walnut is very hardy indeed. It can survive temperatures as low as minus 45 degrees Celsius. It does not like shade however, and needs moist alkaline soil to thrive. It is fragile in its early years, with sticky and hairy branches, but once established it can reach a height of 25 m.
The tree does produce chemicals to suppress the growth of competitor trees (known as allelopathy), but less so than other walnuts – and this is not a significant problem in cultivation.
Cultivation and uses
This tree produces edible nuts, but compared to the more common walnut they are small and difficult to extract from a very thick shell.
The Chinese walnut is a popular ornamental plant, and its roots are used for grafting on to less hardy species, to help them benefit from its exceptional resistance to cold.
- Scientific name: Juglans cathayensis
- Family: Juglandaceae
- Place of origin: north-eastern former USSR, north-eastern China and Korea. This species was brought to the UK in 1903 by intrepid botanist Ernest 'Chinese' Wilson.
- Conservation status: Least Concern
- Date planted: 1982
- Height: 11.2 m. This is a small specimen as theoretically the species can grow up to 25 m.