Common names: Black Walnut, Eastern American Black Walnut 

Latin name: Juglans nigra 

Family: Origin: Non-native 

Tree type: Broadleaf (Broadleaf vs Conifer) 

How it looks 

Shape, bark, twigs 

It is a tall, deciduous, light-loving tree with a big domed crown that can reach heights of up to 40m. The bark is smooth when young, becoming dark and fissured as the tree matures.  

Leaves 

It has long pinnate bright green leaves with many leaflets – up to 23. Each leaflet has an oval shape, tapers to a point, and features irregularly spaced teeth along its edges. On the lower surface of the leaflets is a mix of glandular and non-glandular hairs. The leaves are highly aromatic when crushed. In Autumn they turn a very vibrant yellow before falling. 

Flowers 

From late May to early June, both male and female flowers emerge. The male flowers are found on catkins that are 8–10 cm long and hang down from the branches, while the female flowers appear in clusters. 

Fruits 

The flowers turn into a hard round fruit that encases the nut. These cases can be very hard making it difficult to access the nut. Nuts can be produced by young trees, but it takes approximately 20 years for full production and quantities can vary hugely from year to year. Unlike the common walnut, the black walnut's husk secretes a potent dark dye that readily stains skin, leaving persistent marks on fingers and hands. 

Similar species 

The common walnut Juglans regia (Juglans regia) features more compact foliage, with notably smaller leaves and leaflets compared to other walnut species 

Where to find it

There are 15 different species of Walnut found throughout the Americas and Asia. Black Walnut is native to North America. They are often found to be grown singly instead of groups as they crave light. 

Cultural importance

History | Art and Literature

History

The latin name for walnut, Juglans, comes from the conjoined words ‘Jovis’ meaning Jupiter and ‘glans’, which translates as ‘an acorn’. 

The discovery of black walnut shells on Indigenous archaeological sites throughout different parts of North America, demonstrates that First Nations peoples have had a connection with the black walnut for thousands of years. The tree was important to many First Nations, including the Appalachian, Chippewa, Cherokee, Comanche, Iroquois, and Rappahannock, and features frequently in their creation stories.  

First Nations used different parts of the tree for a variety of purposes. The nuts of the tree were crushed and used to make bread, puddings, soups and drinks. Black walnut also had a range of medicinal properties. The bark was used to treat toothache, digestive issues, snake bites and smallpox. The leaves were used to treat thyroid issues, sores, ringworm and athlete’s foot. In addition, black walnut wood was also very important to these First Peoples, and was widely used for carving, construction and to make furniture. Other domestic uses included making dye from the bark, roots, husks, nuts and leaves. The nuts were also used to make mosquito repellent. 

It is unsurprising that the early European settlers arriving in North America in the seventeenth century quickly recognised the value of the black walnut and used it for various purposes such as fuel, fencing, furniture making, dying and as a food source. The group of settlers known as the Pennsylvania Dutch had a particular affinity with the black walnut and became renowned for their black walnut cabinetry. They also preferred to settle in areas where black walnuts grew as they were an indicator of fertile land. 

Black walnut also became important during wartime as it was used to manufacture guns, and during the American Civil War, the hulls of the walnut were used to dye the uniforms of Confederate soldiers. In addition, during World War I, black walnut was used to make airplane propellers for the United States government.  

Unfortunately, due to its immense value, especially with regard to arms and military use, black walnut populations became significantly depleted by the 1930s. Managed tree planting programmes have since increased their numbers. Black walnuts have continued in their popularity down through the years, to the degree that they have even been poached from private properties. 

In terms of the wider distribution of black walnut outside of North America, the early settlers sent walnut seeds to Europe in the early 1600’s where it became a popular ornamental tree and was also cultivated for its timber. The black walnut was introduced to England by the gardener and collector John Tradescant the Younger in the 1650’s and likely made its way to Ireland around the same time. Beautiful examples of black walnut can be found today on the grounds of the Trinity College Botanic Gardens, Dublin and the University College Cork arboretum. 

Art and Literature 

Perhaps one of the most famous pieces of North American literature on the black walnut is the Canadian novel, The Trail of the Black Walnut, in which the author George Elmore Reaman describes how a group of Pennsylvania Dutch settlers followed the black walnut in search of fertile land. It also features in Mary Oliver’s beautiful poem, The Black Walnut Tree, in which she demonstrates the prized nature of the black walnut through a narrative concerning a family who are forced to consider selling their walnut tree that is of great sentimental value in order to pay their mortgage. 

Value to wildlife

Various wildlife, including squirrels and several bird species, eagerly consume the nutritious black walnut nuts.

Threats

Black walnut trees face critical threats from Thousand Cankers Disease, invasive pests, climate stress, and habitat destruction. 

Uses

The black walnut tree produces edible nuts and strong timber and is often planted as an ornamental tree due to its outstanding autumn colour.

Reference/Further Reading

White, J. White, J. Walters, J. (2005). Trees: A field guide to the trees of Britain and Northern Europe. Oxford. 

Drori, J. (2018) Around the World in 80 Trees. London: Laurence King Publishing 

Sterry, P.(2007) Collins Complete British Trees. London: Collins. 

Kingsbury, N. (2015) Hidden histories: Trees. Timber Press 

Adkins Arboretum. 2024. Black Walnut, Adkins Arboretum Indigenous Peoples' Perspective Project. Black Walnut : Indigenous Peoples' Perspective Project : Programs | Events : Adkins Arboretum 

Andersen, M. K. 2003. Black Walnut - Juglans nigra L., USDA NRCS National Plant Data Center. BLACK WALNUT (usda.gov) 

Dahlem, G. G. 2014. Black Walnut: The Multi-Purpose All American Tree, Small Farmers Journal, 38(3). Black Walnut: The Multi-Purpose All American Tree - Small Farmer's JournalSmall Farmer's Journal (smallfarmersjournal.com) 

Eurforgen. 2024. Juglans Nigra – Black Walnut. European Forest Genetic Resources Programme. Juglans nigra - EUFORGEN European forest genetic resources programme 

Oliver, M. 1979. The Black Walnut Tree. Ronnowpoetry.com. The Black Walnut Tree (ronnowpoetry.com) 

Reading Eagle. 2016. The Historian: Black walnuts in local folk culture, Reading Eagle Newspaper. The Historian: Black walnuts in local folk culture – Reading Eagle 

Reaman, G. E. 1957. The Trail of the Black Walnut, Toronto: McClelland and Stewart. 

Sutton, J. 2019. Juglans nigra, Trees and Shrubs Online. Juglans nigra - Trees and Shrubs Online 

Trinity College Dublin. 2023. Trinity tree of the month - Black Walnut, Trinity College Dublin News and Events. Trinity tree of the month - Black Walnut - News & Events | Trinity College Dublin (tcd.ie) 

University of Vermont. 2024. Eastern Black Walnut (Juglans nigra L.): Other Historical Uses: Dye, Wood, and Industrial Applications, UVM Digital Exhibits. Omeka@CTL | UVM Tree Profiles : Eastern Black Walnut (Juglans nigra L.) : Other Historical Uses: Dye, Wood, and Industrial Applications 

Woodland Trust. 2024. Black Walnut, Woodland Trust. Black Walnut (Juglans nigra) - British Trees - Woodland Trust