Botanical Name: Juglans nigra.
Other Common Names: American walnut, eastern black walnut.
Habitat: Black walnut is a deciduous hardwood tree native to North America, prized for its beautiful dark-colored heartwood.
It grows in small groups or as scattered individuals in the fertile moist soils of mixed hardwood forest. It can also be found in pastures, meadows, and slopes.
Its natural range extends from western Vermont and Massachusetts west to eastern South Dakota; south to Texas and Florida.
Black walnut does well in a range of soil conditions, from light (sandy), medium (loamy) and heavy (clay) soils that range from acid, neutral to basic (alkaline).
Plant Description: Black walnut is a large tree that grows to a height of 150 feet with a trunk diameter of up to 5 feet. Its crown is broadly rounded; the trunk is straight and columnar, not buttressed at the base, with thick, deeply furrowed black bark.
Twigs are stout, greenish to orange-brown, hairy, smooth and gray with brown pith divided by chambered partitions. Only the black walnut and a close relative, the butternut, have chambered pith.
The buds are somewhat rounded at the tip, soft, pale brown, up to ½ inch long. The leaves are alternate, pinnate compound with 15-23 leaflets up to 31/2 inch wide.
The leaflets are broadly lance-shaped, pointed at the tip, rounded at the asymmetrical base and toothed along the edges. They are yellow-green and smooth on the upper surface, paler and hairy on the lower surface, turning yellow in the autumn.
The monoecious flowers are either male or female but both sexes can be found on the same tree. The flowers are wind-pollinated and the tree is self-fertile. The flowers appear in May and June when the leaves are partly grown; the staminate several in thick, yellow-green hairy catkins.
The pistillate are much fewer in small spikes; neither flower has petals. The seeds ripen in October, growing up to 2 inches in diameter in groups of 1 or 2. They are spherical, green or yellow-green, slightly roughened with a thick husk covering the hard, oval dark brown deeply ridged nut.
Plant Parts Used: Bark, nut and leaves.
Health Benefits, Therapeutic Uses and Claims of Black Walnut
Active ingredients in the black walnut hull include omega-3 fatty acids, sterols, tannins and iodine. Black walnut shells are very rich in vitamin C; and beta-carotene, B1, B2, and B6 are found in the leaves.
The tannins in the hull are antibacterial, anticancer, antidiarrheic, anti-hepatoxic, chelator, antihypertensive, antitumor, cancer preventive, antiulcer. Iodine is antiseptic and antibacterial.
The bark and leaves of the black walnut are alterative, anodyne, astringent, blood tonic, detergent, emetic, laxative, pectoral and vermifuge.
Black walnut is especially useful in the treatment of skin diseases such as herpes and eczema. Traditionally it is used as a natural remedy for acne, canker sores, psoriasis and other fungal infections.
The juice of the fruit husk may be applied externally as a treatment for ringworm or applied as a poultice for inflammations.
The oil from the ripe nuts is a traditional remedy for gangrene, leprosy, and wounds.
Black walnut is used in traditional herbal medicine to expel worms, parasites and harmful pathogens from the body. It is suggested that the natural tannins present in black walnut alters the pH of the intestine which may help in killing fungus, parasites and yeast, and expel worms and parasites.
Studies have shown that black walnut may be useful in treating cell damage caused by liver injury due to exposure to certain environmental toxins such as carbon tetrachloride.
The nuts of the black walnut are believed to aid in decreasing cholesterol levels and to improve overall heart health and function.
The iodine in black walnut shells has antiseptic properties which can increase the immune system’s response time when fighting bacteria and infection.
Some studies have shown that black walnut significantly reduced total cholesterol and LDL-cholesterol concentrations, and may be useful as a treatment for high blood pressure. It is high in Omega-3 fatty acids, which are beneficial to heart health.
The nuts may also be helpful as a natural control for diabetes, due to the Omega-3 fatty acids which lower the level of triglycerides (bad cholesterol) and increase the level of HDL (good cholesterol) which in turn may help in controlling the level of sugar in the blood.
The presence of Omega-3 fatty acids in the fruit of the black walnut can help reduce inflammation and promote the function of the lungs; this may give relief from asthma.
The presence of juglone, omega-3 fatty acids, phytosterols, polyphenols, carotenoids and melatonin in black walnut may have anti-tumor properties which may help in the treatment of cancer.
Dosage and Administration
Commercially available tablets or capsules contain usually around 500 mg – 1000 mg of powdered black walnut.
The oral doses are generally taken three times a day but no longer than 6 weeks because of the high tannin content of black walnut. Otherwise, the manufacturer’s instructions should be followed carefully.
Side Effects and Possible Interactions of Black Walnut
In rare cases, black walnut may cause rashes, swollen skin, hives, and skin irritation.
Rarely, chest pain, tightness of the airways, and breathing difficulties have been associated with the use of black walnut. Black walnut is not advised for use during pregnancy or while breastfeeding.
It may interact with certain medications, so a health care professional should be consulted regarding medications, vitamins or other herbs prior to use.
As with all herbs and supplements, it is vital that they are purchased from a reputable source to ensure the product is of a high quality.
Meyer, Clarence: American Folk Medicine. Glenwood, Illinois. Meyerbooks 1973.
Meyer, Clarence: Planetary Herbology. Glenwood, Illinois. Meyerbooks 1992.
Forey, Pamela and Ruth Lindsa: An Instant Guide to Medicinal Plants. Crescent Books 1992.
Hylton, William H: The Rodale Herb Book: How to Use, Grow, and Buy Nature’s Miracle Plants. Rodale Press, Inc 1974.
Ody, Penelope: The Complete Medicinal Herbal. 232 Madison Avenue, New York. Dorling Kindersley, Inc 1993.