by
John Marshall
The
black walnut (Juglans nigra) was once the most valuable hardwood tree in
North America and certainly one of the most prized among cabinet makers,
gunsmiths and other woodworkers. There is no other wood like it: beautiful,
strong, easy to work and resistant to rot. The black walnut is definitely one
of North America's most remarkable trees, both for its uses and its natural
beauty.
Black
walnut trees are found throughout the eastern and central United States and
into southern Ontario. Naturally occurring trees prefer deep, rich bottomland
soils, mostly along forest edges. They are frequently found in pastures and
along roadsides, where there is plenty of light. It is a tree capable of reaching
heights of more than 100 feet, with some specimens reported to have reached 150
feet tall and 8 feet in diameter. Trees of that size are extremely rare now,
however.
The
bark is black and deeply grooved, and the top branches spread out to form a
wide crown. The leaf of the black walnut is pinnately compound, which means it
is made up of numerous leaflets on a central leaf stem (petiole). The number of
leaflets per leaf varies, usually numbering around 15 or 20. The leaflets are
yellowish-green during the growing season, changing to a dull yellow in autumn.
Separate male and female flowers occur on the same tree. They are small, with
no petals, hanging in long strings called catkins (like the flowers of oak
trees). One distinctive identification trait found on black walnuts and their
close relative, the butternut (Juglans cinerea), is the pith. When a
twig is cut and the interior material examined, it will appear chambered, like
a honeycomb.
The
fruit is a large nut, around 2 inches in diameter and surrounded by a thick
green husk that turns dark brown to black after the nut falls from the tree.
The outer part of the nut (shell) is very hard, black in color with fine
ridges. Nuts grow singly or in clusters of two or three. The meat of the nut is
high in oil and very nutritious; it’s a favorite food of squirrels and deer,
not to mention people. Walnut trees begin producing nuts at around 10 years of
age and continue to produce their entire lives (up to 200 years). Walnut Uses
The
black walnut tree has been prized for more than 300 years for its many
excellent qualities. The heartwood (the wood closest to the center of the tree)
of a mature black walnut is dark brown with a straight grain. It’s an easy wood
to work and extremely durable. During colonial times, when large trees were
still abundant, solid black walnut wood was used to make all manner of
furniture.
By
the mid-1800s, most of the really large trees were gone, but walnut continued
to be used to make everything from fence posts and railroad ties (because it
didn’t rot easily) to gunstocks. Today, black walnut is still prized for use in
gunstocks, because it doesn’t warp or splinter and absorbs recoil better than
any other wood.
Another major use of black walnut is as a veneer.
Veneer is made by slicing the wood to create very thin (about 1/28th of an inch
thick) sheets and gluing the sheets to paneling and cabinets. Trees used for
veneer are typically at least 16 inches in diameter and preferably larger. The
best trees for lumber grow in natural, woodland settings, where the trunk tends
to grow straighter with a smaller crown of spreading branches at the top. These
trees produce better and larger logs, as well as the darker heartwood prized
for furniture.
There are numerous “urban myths” associated with
the value of black walnut trees, especially those growing in residential
environments. Claims have been heard of a single tree bringing thousands of
dollars. As with any tree species, the value is based on many factors, such as
current demand, supply and the quality of the wood. If you have black walnut
trees you are thinking about selling, first check with a consulting forester or
your state forestry agency and determine the value of the trees in question.
In addition to the tree’s valuable lumber, the walnuts
themselves are extremely valuable. While most commercially sold nuts (Persian
walnuts, pecans, macadamia) are grown in orchards, a substantial portion of the
black walnut harvest comes from naturally growing stands of trees. The best nut
trees grow in open areas where they develop a widespread crown of branches.
While the annual harvest of black walnuts is small compared with Persian
(sometimes called English) walnuts, a demand for them always exists.
The nut meat is used for baking and in ice cream and
walnut stain is derived from the husks of ripened walnuts. During World War I,
not only were gunstocks made from walnut wood, the woody hulls of walnuts were
ground up to make activated charcoal for use in gas masks. Walnut hulls have
also been used as abrasives to clean jet engines and to assist in drilling oil
wells. Native Americans ground up the green husks of black walnuts to use as a
poison (that didn’t affect people) to catch large numbers of fish. Extracts
from black walnut hulls are used to treat a variety of internal and external
parasites in both humans and animals.
The problem with walnuts
For all the wonderful products we derive from the
black walnut tree, it is not without its drawbacks. Walnut and butternut trees
get part of their scientific name, Juglans, from a chemical they produce
called “juglone.” Juglone is an allelopathic chemical, meaning it inhibits the
growth of other plants in the vicinity of the tree, reducing competition for
water and nutrients. While not all plants are sensitive to juglone, tomatoes,
potatoes, hydrangeas, blueberries and apple trees are very sensitive.
Horses seem to be sensitive to black walnuts as
well, often developing respiratory problems when exposed to pollen and fallen
leaves of this tree. Bedding material that contains black walnut shavings has
also been shown to cause inflammation of the hooves in horses. Dogs have also
gotten sick from eating the seeds and chewing on the hulls of black walnuts.
Of course, many folks with black walnut trees
close to their homes complain about the large nuts falling in the fall. To them
it represents one more hassle in maintaining their yard. Black walnuts are also
difficult to crack open, owing to their thick hulls, and most people don’t want
to bother with them.
Walnuts for the future
Walnuts for the future
While black walnut trees are not the major source
of furniture and other products that they were two centuries ago, demand for
this remarkable tree and its many products remains high. Having black walnut
trees on your land or planting a large stand of them could potentially produce
a steady source of income for years to come. As with most hardwood species,
black walnut trees take many years to mature and may not be ready for harvest
in the landowner’s lifetime. They may, however, represent a significant legacy
for children or grandchildren, while providing a variety of other marketable
products for landowners.
John Marshall teaches environmental and safety
technology and biology at Pulaski Technical College in North Little Rock,
Arkansas. He grew up on a small farm in northern Alabama and has never lost his
love of the land. John, his wife, three children, a dog, a cat and a parakeet
live in the small town of Benton.
Wow, this is very interesting ! Now, let's hope they grow !
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