Black Walnut: History and Traditional Use

Table of Contents

1. A Tree of the Eastern Forests: Botany and the Name
2. The First Peoples of Walnut Country: Food, Dye and Medicine
3. Brown Hands and Black Ink: The Dye Tradition
4. The Timber Tree: Furniture, Veneer and Gunstocks
5. Nineteenth-Century Medicine: The Eclectics and the Dispensatories
6. From Nucin to Juglone: The Chemistry (1856–1887)
7. "Nothing Grows Under a Walnut": The Allelopathy Story
8. A Veterinary Chapter: Walnut Shavings and Laminitis
9. The "Parasite Cleanse" Revival and What the Laboratory Says
10. Black Walnut Today: Nuts, Conservation and Thousand Cankers Disease
11. Key Research Papers
12. Connections
13. Featured Videos

A Tree of the Eastern Forests: Botany and the Name

Black walnut is a large deciduous tree of the walnut family, Juglandaceae, native to the eastern half of North America. Its natural range runs from southern Ontario and the southern edges of Minnesota, Wisconsin and Michigan south to Georgia and northern Florida, and west through the Mississippi valley to southeastern South Dakota and central Texas. It is a tree of rich, moist bottomland: it grows fastest along rivers and in deep, well-drained soils, and it does poorly in shade, which is why old walnuts so often stand alone at the edge of a field rather than deep inside a forest. A mature tree commonly reaches 70 to 90 feet; its thick, near-black bark is furrowed in a diamond pattern, and each compound leaf carries nine to twenty-three leaflets.

The genus name Juglans is Roman. The Latin nux simply meant "nut," and the walnut in particular was Jovis glans, "Jupiter's acorn" — the story being that while mortals of the golden age lived on acorns, the gods dined on walnuts. Linnaeus kept the Roman name for the genus, and the epithet nigra ("black") describes the dark bark and heartwood. The Romans never saw this species: their walnut was Juglans regia, the "royal" or Persian walnut, which Pliny the Elder said had come to Italy from Persia. That Old World tree is the walnut of grocery shelves and of nearly all the European herbal literature.

Two relatives cause persistent confusion. When a medieval or Renaissance herbal says walnut, it means J. regia. And the butternut or white walnut, Juglans cinerea, shares much of black walnut's range, with lighter, softer wood, an oilier oblong nut and yellow-to-brown dyes of its own; much nineteenth-century American medicine that reads "walnut" is in fact butternut. Butternut is now endangered, devastated by butternut canker; black walnut is not, though it has its own disease story, told at the end of this article.

Back to Table of Contents

The First Peoples of Walnut Country: Food, Dye and Medicine

Long before European contact, black walnut was woven into the life of every nation whose territory it grew in, and the ethnobotanical record — plant uses gathered by anthropologists from the early twentieth century onward and compiled in Daniel Moerman's Native American Ethnobotany database — lets us say which peoples used it for what, on the authority of named fieldworkers. The uses below are recorded traditions, not claims that the remedies worked.

Food came first. The Iroquois are documented crushing fresh nutmeats into corn soup, hominy, corn bread and corn pudding, boiling them to skim off an oil that was salted and used as a gravy, and adding that oil to the ceremonial mush of the False Face societies. The Cherokee dried the nuts in the rafters for winter and cooked them with skinned hominy corn and beans; the Dakota made a nut soup and ate the kernels plain or with honey; the Comanche stored the nuts for winter. Black walnut is a "mast" tree — it fruits heavily in some years and hardly at all in others — so a good crop was something to gather and put by.

Dye was the second great use. The Chippewa (Ojibwe) made black and dark-brown dyes from the bark; the Cherokee used bark, roots and husks for brown and the leaves for green; the Dakota made black from the nuts and the roots. The colour comes from the same compounds that stain the hands of anyone who hulls a fresh walnut, and it is exceptionally fast — it needs no mordant (the metal salt most plant dyes require to fix them to cloth), which is one reason walnut brown survived into the settler kitchen.

Medicine was the third. The pattern across nations is remarkably consistent and maps closely onto the later folk and commercial uses. The Comanche rubbed pulverised leaves on ringworm; the Delaware rubbed the juice of the green hulls over ringworm and applied the sap to inflammations, and their Oklahoma communities were still doing so when Gladys Tantaquidgeon recorded their medicine in 1942. The Cherokee used an infusion of the bark as a wash for sores and chewed the bark for toothache — while noting, in the words their ethnographers preserved, that the bark had to be "used cautiously in medicine because it is poisonous." The Iroquois took a compound decoction of the bark as a laxative and poulticed it for headache; the Delaware took a strong bark tea as a cathartic and emetic and "to remove bile from the intestines"; the Houma of Louisiana washed "the itch" with an infusion of the nut shells. The Delaware also scattered the leaves about the house to dispel fleas, a use Ozark households kept up into the twentieth century. Notice what recurs: skin fungus, purging and insects — the three things the plant's chemistry, described below, demonstrably acts on in a dish.

Back to Table of Contents

Brown Hands and Black Ink: The Dye Tradition

Settlers adopted the walnut dye at once: on a frontier without imported dyestuffs, walnut hulls gave a deep, permanent brown to wool and linen with nothing more than a kettle and a fire. Nineteenth-century medical texts mention it as common knowledge — King's American Dispensatory notes that butternut bark and shells "furnish a dye of a chocolate color, for woolen goods, but as a dye, the bark of the black walnut is preferable." Early settlers are also recorded using the hull extract as a hair dye, and hull-water was a household ink and wood stain long before commercial stains existed. The colouring agents are juglone (a quinone that darkens on oxidation), the related pigment plumbagin and a heavy load of tannins. The dye is still used by hand-dyers and woodworkers, and ground hulls have found an unromantic modern market as an abrasive.

One popular story needs correcting. The Confederate infantry of the American Civil War were nicknamed "butternuts," and it is often said that black walnut dyed their uniforms. The nickname refers to Juglans cinerea, the butternut, whose bark and husks produce colours from light yellow to dark brown, and the historical record is itself equivocal: some Confederate uniforms appear simply to have faded from grey toward tan, and butternut dye is thought to have coloured the homespun of only a minority of soldiers. Black walnut was in the dye-pots of the period, but the "butternut" of the history books is its cousin.

Back to Table of Contents

The Timber Tree: Furniture, Veneer and Gunstocks

For most of the last three centuries black walnut's chief value to Americans has been as wood, not medicine. The heartwood is a rich chocolate brown, dense, stable once dry and unusually easy to work; it takes a polish and holds fine carving. The U.S. Forest Service's Silvics of North America lists its principal uses as dining-room and bedroom furniture, bookcases, desks and tables, with the best logs sliced into veneer for the highest grade of cabinets and plywood panels. The Cherokee are recorded making furniture, carvings and gunstocks from it, and "figured" walnut — wood with wavy or feathered grain, often from the stump or a crotch — remains the stock of choice for expensive shotguns and sporting rifles because it is strong, shock-absorbing and beautiful. Two centuries of selective cutting have made a veneer-grade walnut a rare and valuable tree, and that value is what later made the allelopathy question — what the tree does to crops planted beside it — worth the science. The wood also went into flooring, paddles, coffins and, in the Ozarks, was "used lavishly in homes, barns, and fences."

Back to Table of Contents

Nineteenth-Century Medicine: The Eclectics and the Dispensatories

American physicians of the nineteenth century inherited both the Native American uses and the European reputation of the Old World walnut. Maud Grieve's A Modern Herbal (1931), summarising centuries of European practice with Juglans regia, credits the bark and leaves with "alterative, laxative, astringent and detergent properties" for "scrofulous diseases, herpes, eczema, etc., and for healing indolent ulcers," and says of the green husks and unripe nuts that they possess "worm-destroying virtues" — the vermifuge (worm-expelling) reputation that would attach itself to the American species. In old medical language an alterative was a remedy believed to gradually restore health in chronic disease, and scrofula was tuberculosis of the lymph nodes of the neck; both terms describe a category of slow, disfiguring skin and gland disease for which walnut preparations were a standard prescription.

The Eclectics — the school of American physicians who built a practice around native plants from the 1830s to the early twentieth century — were the great codifiers. Their reference work, King's American Dispensatory (the 1898 edition by Felter and Lloyd is the one usually cited), gives the Juglans entry primarily to butternut, the root bark of J. cinerea: in small doses "a mild stimulant to the intestinal tract, proving laxative and in larger doses ... a gentle and agreeable cathartic," an "efficient alterative in chronic skin affections and scrofula," and, the authors add with evident pride, a remedy "used with great advantage in the treatment of dysentery and diarrhoea occurring among our soldiers in the Civil War." Black walnut appears in the same entry chiefly for two things: a decoction that "has been used to remove worms," and its superior bark dye. Folk practice, meanwhile, kept the green-hull juice as a remedy for ringworm and other skin fungus — exactly the Delaware and Comanche use — and a tincture of the green hulls in alcohol became the standard preparation, the form still sold today.

Note what the Eclectics did not claim: a purge, a skin wash and a traditional worm remedy, never a cure for systemic infection or cancer. That inflation came a century later.

Back to Table of Contents

From Nucin to Juglone: The Chemistry (1856–1887)

The chemistry of the walnut's brown began, appropriately, with the stain. In 1856 the chemists Vogel and Reischauer isolated a crystalline colouring matter from walnut and named it nucin, from the Latin nux. The name that stuck came from the genus: juglone. Working out what the molecule actually was took another three decades, and the decisive papers were a series by August Bernthsen and August Semper in the Berichte der deutschen chemischen Gesellschaft between 1884 and 1887, culminating in a paper on "the constitution of juglone and its synthesis from naphthalene." Juglone turned out to be 5-hydroxy-1,4-naphthoquinone: a two-ring naphthalene skeleton carrying a quinone (two opposed carbonyl groups that make the molecule a ready oxidising agent) and a single hydroxyl group. That structure explains almost everything else in this article: quinones cycle between oxidised and reduced states, generating reactive oxygen species and attacking sulfur groups in proteins — small chemical weapons that plants of many families deploy against microbes, insects and neighbours.

Later work added a key detail. In the living tree, juglone is held mostly in a colourless, reduced, sugar-bound form; when tissue is bruised, cut or shed, that precursor is oxidised on contact with air to the brown-black juglone that stains hands and driveways. This is why fresh green hulls, buds and roots — the parts richest in the precursor — are the parts that dye, poison and medicate. As Charles Soderquist noted in a 1973 review for chemistry teachers, juglone was prescribed in America in the early 1900s for skin diseases, and was at the same time the first allelopathic compound ever identified.

Back to Table of Contents

"Nothing Grows Under a Walnut": The Allelopathy Story

Every gardener in walnut country knows that tomatoes wilt and die within reach of a black walnut's roots, and that the ground under an old tree is oddly bare. The observation is ancient: reviews of juglone trace it to the first century CE, and it is usually credited to Pliny the Elder's Natural History, which remarks on the heavy, harmful shade of the walnut — the Old World species, but the same family and the same chemistry. What the Romans put down to shade, chemistry eventually put down to juglone. The first scientific report connecting the compound to the effect appeared in 1881, a quarter-century after its isolation.

The question became urgent in the United States in the 1920s, when farmers and orchardists began to blame walnuts for real economic losses and plant pathologists went to look. In 1921 M. T. Cook reported in Phytopathology on tomato plants wilting near walnut trees; in 1926 F. J. Schneiderhan's apple-disease studies in northern Virginia documented apple trees damaged by both black walnut and butternut, some varieties proving more resistant than others; and by 1928 A. B. Massey was asking in print whether nut trees were "poisonous to other trees and plants." There was resistance — one 1926 farm journal insisted the offending Virginia trees were not walnuts at all — and the toxin was awkward to study because it dissolves poorly in water. By 1942 experiments had shown that pieces of walnut root alone stopped tomato and alfalfa seed from germinating. In 1937 the Austrian plant physiologist Hans Molisch gave the whole phenomenon a name, allelopathy, the chemical suppression of one plant by another, and black walnut became its textbook example, taught to generations of students through papers like Soderquist's.

The modern chapter is more nuanced. Field and hydroponic studies of walnut–corn "alley cropping" in the 1990s measured real juglone in the soil and real losses in corn and soybean growth, yet a 2019 reassessment questioned how much of the tree's success is chemical rather than the ordinary shade and root competition of a large tree, and there is no scientific consensus that allelopathy is its primary weapon. What is not in dispute is that juglone is a respiratory inhibitor to sensitive plants — tomatoes, apples, alfalfa — and that grasses and many other species shrug it off.

Back to Table of Contents

A Veterinary Chapter: Walnut Shavings and Laminitis

The plant's toxicity is not confined to tomatoes. In the late 1970s and early 1980s American veterinarians began to notice that horses bedded on fresh wood shavings containing black walnut developed laminitis — a painful, potentially crippling inflammation of the sensitive tissues that bond the hoof wall to the bone inside it — within hours. Ralston and Rich described "black walnut toxicosis in horses" in the Journal of the American Veterinary Medical Association in 1983, and a 1989 report in the same journal followed ten affected horses. Then the effect was reproduced deliberately: Minnick and colleagues induced laminitis in 1987 with an aqueous extract of black walnut heartwood given by stomach tube, and Galey and colleagues in 1991 developed "black walnut toxicosis" into a formal experimental model of the disease.

That model has had a long afterlife. Because it produces the early stage of laminitis on a predictable timetable, black walnut extract became for two decades one of the standard ways of studying how the disease begins, and a large body of equine research on white-cell activation, inflammatory signalling and hoof blood flow was done with it, summarised by Belknap in 2010 as "an inflammatory model." Two cautions belong here. The exact toxic principle has never been settled; juglone is the obvious suspect, but the extracts have not been shown to act through it alone. And this is a story about horses standing in walnut sawdust, not people taking hull tincture — though it is the clearest documented case of black walnut harming a large mammal, and a reminder that a plant which stops seeds germinating and kills fungi is biologically active in the ordinary, double-edged sense.

Back to Table of Contents

The "Parasite Cleanse" Revival and What the Laboratory Says

For most of the twentieth century black walnut hull tincture was a minor item in herbalists' catalogues. Its modern fame dates from 1993, when a self-published book by an alternative-medicine author proposed that parasites — and a particular intestinal fluke in particular — were the cause of cancer and most other chronic disease, and offered as the remedy a three-herb programme of black walnut hull tincture, wormwood and cloves, said to "rid you of over 100 types of parasites." The trio became the template for the "parasite cleanse" kits still on shelves today. The public record is short and clear: no study has supported the underlying theory, the fluke named does not occur in North America or Europe, and the U.S. Federal Trade Commission later required marketers of such products to stop making disease claims for them without "competent and reliable scientific evidence." None has been produced since.

It is important to separate that claim from the genuine laboratory science, which is real but modest. In 1990 Clark, Jurgens and Hufford, prompted explicitly by the folk use of hull juice for ringworm, tested juglone against a panel of bacteria and fungi and compared it with standard antifungal drugs; juglone was active in the dish. Since then in-vitro work has confirmed that juglone inhibits common bacteria such as Staphylococcus aureus and Escherichia coli, several skin fungi and some protozoa, and has begun to identify which other phenolics in the hull and kernel share that activity. What the record does not contain is a randomised clinical trial of black walnut hull, alone or in the three-herb combination, against any human parasitic infection — and juglone's own cytotoxicity and mutagenicity in cell assays mean such a trial would face hard safety questions. The honest summary is that tradition asked a reasonable question about skin fungus and worms, the laboratory has partly answered the first, and the marketplace answered the second before anyone had looked.

Back to Table of Contents

Black Walnut Today: Nuts, Conservation and Thousand Cankers Disease

The nut itself deserves the last word, because it is the one use that has never gone out of fashion. Black walnut kernels have a strong, earthy flavour quite unlike the mild Persian walnut, and they are still gathered largely from wild trees: every autumn people across the Ozarks and lower Midwest collect the fallen nuts and sell them to hulling stations. Missouri accounts for roughly two-thirds of the American wild harvest, and the kernels go mostly into ice cream, baked goods and confections. Nutritionally the kernel resembles other tree nuts — rich in unsaturated fats, protein, ellagitannins and other phenolics — and the site's page on walnuts covers the food science.

As a species, black walnut is secure: the IUCN Red List assessed it as Least Concern in 2018. But the last two decades have brought a genuine threat. In 2001 foresters recorded an unexplained cluster of black walnut deaths in the Española valley of northern New Mexico, and similar die-offs followed across the western states, where the tree had been planted far outside its native range. In 2008 the city of Boulder, Colorado, removed some 700 dying walnuts, and researchers at Colorado State University worked out what was killing them: a tiny native bark beetle, the walnut twig beetle (Pityophthorus juglandis), was tunnelling under the bark in enormous numbers and carrying a previously unknown fungus that raised a small canker at every entry hole — thousands per tree, hence "thousand cankers disease." Tisserat and colleagues described the Colorado outbreak in 2009, and in 2011 Kolařík, Freeland, Utley and Tisserat formally named the fungus Geosmithia morbida in the journal Mycologia, the first member of its genus ever shown to be a plant pathogen. The alarm deepened when the disease turned up in the Knoxville area of Tennessee, inside the native range, almost certainly carried there in infested wood. The largest known black walnut in North America, on Sauvie Island in Oregon, was felled in 2020 after succumbing to it.

So the tree that once had the eastern bottomlands to itself, and the chemistry to keep neighbours at a distance, now depends on the people who value it — for its nuts, its timber, its dye, and the old, still-open questions about its medicine — to keep it from travelling where its enemies wait.

Back to Table of Contents

Key Research Papers

The list below gathers the genuine historical chemistry of juglone, the twentieth-century allelopathy and veterinary literature, modern reviews of the compound's biology and laboratory antimicrobial activity, and the papers that described thousand cankers disease. Historical primary texts (King's American Dispensatory, Grieve's A Modern Herbal, the ethnobotanical field reports compiled in Moerman's database) are named in the article rather than cited here.

1. Bernthsen A, Semper A (1887). Ueber die Constitution des Juglons und seine Synthese aus Naphtalin. Berichte der deutschen chemischen Gesellschaft. — doi:10.1002/cber.188702001213
2. Soderquist CJ (1973). Juglone and allelopathy. Journal of Chemical Education. — doi:10.1021/ed050p782
3. Ahmad T, Suzuki YJ (2019). Juglone in Oxidative Stress and Cell Signaling. Antioxidants. — doi:10.3390/antiox8040091
4. Clark AM, Jurgens TM, Hufford CD (1990). Antimicrobial activity of juglone. Phytotherapy Research. — doi:10.1002/ptr.2650040104
5. Ho KV, Schreiber KL, Vu DC, Rottinghaus SM, Jackson DE, Brown CR, Lei Z, Sumner LW, Coggeshall MV, Lin CH (2019). Black Walnut (Juglans nigra) Extracts Inhibit Proinflammatory Cytokine Production From Lipopolysaccharide-Stimulated Human Promonocytic Cell Line U-937. Frontiers in Pharmacology. — doi:10.3389/fphar.2019.01059
6. Ralston SL, Rich VA (1983). Black walnut toxicosis in horses. Journal of the American Veterinary Medical Association. — PubMed PMID: 6643218
7. Galey FD, Whiteley HE, Goetz TE, Kuenstler AR, Davis CA, Beasley VR (1991). Black walnut (Juglans nigra) toxicosis: a model for equine laminitis. Journal of Comparative Pathology. — PubMed PMID: 2061431
8. Belknap JK (2010). Black walnut extract: an inflammatory model. The Veterinary Clinics of North America. Equine Practice. — PubMed PMID: 20381738
9. Tisserat N, Cranshaw W, Leatherman D, Utley C, Alexander K (2009). Black Walnut Mortality in Colorado Caused by the Walnut Twig Beetle and Thousand Cankers Disease. Plant Health Progress. — doi:10.1094/php-2009-0811-01-rs
10. Kolařík M, Freeland E, Utley C, Tisserat N (2011). Geosmithia morbida sp. nov., a new phytopathogenic species living in symbiosis with the walnut twig beetle (Pityophthorus juglandis) on Juglans in USA. Mycologia. — doi:10.3852/10-124

PubMed Topic Searches

1. PubMed: Black walnut ethnobotany and traditional use
2. PubMed: Juglone history, allelopathy and antimicrobial activity
3. PubMed: Black walnut and equine laminitis

External Authoritative Resources

• USDA NRCS Plant Guide — Black Walnut, Juglans nigra (ethnobotany, description, juglone)
• USDA Forest Service Fire Effects Information System — Juglans nigra (range, wood products, uses)
• Native American Ethnobotany Database (Moerman) — recorded uses of Juglans nigra by nation

Back to Table of Contents

Connections

• All Herbs
• Black Walnut Hub
• Black Walnut Benefits
• Wormwood
• Clove
• Walnuts
• Walnuts: History
• Ellagic Acid
• Ringworm (Tinea)
• Parasites
• Parasite Protocols

Back to Table of Contents

Featured Videos