Juglans Nigra
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''Juglans nigra'', the eastern American black walnut, is a
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of
deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
in the
walnut A walnut is the edible seed of a drupe of any tree of the genus ''Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. Although culinarily considered a "nut" and used as such, it is not a true ...
family,
Juglandaceae The Juglandaceae are a plant family known as the walnut family. They are trees, or sometimes shrubs, in the order Fagales. Members of this family are native to the Americas, Eurasia, and Southeast Asia. The nine or ten genera in the family have ...
, native to
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. It grows mostly in
riparian zone A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...
s, from southern
Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
, west to southeast
South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...
, south to
Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...
, northern
Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
and southwest to central
Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
. Wild trees in the upper
Ottawa Valley The Ottawa Valley is the valley of the Ottawa River, along the boundary between Eastern Ontario and the Outaouais, Quebec, Canada. The valley is the transition between the Saint Lawrence Lowlands and the Canadian Shield. Because of the surroundi ...
may be an isolated native population or may have derived from planted trees. Black walnut is an important tree commercially, as the wood is a deep brown color and easily worked. Walnut
seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...
s ( nuts) are cultivated for their distinctive and desirable taste. Walnut trees are grown both for lumber and food, and many
cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...
s have been developed for improved quality wood or nuts. Black walnut is susceptible to
thousand cankers disease Thousand cankers disease (TCD) is a recently recognized disease of certain walnuts (''Juglans'' spp.). The disease results from the combined activity of the walnut twig beetle (''Pityophthorus juglandis'') and a canker producing fungus, '' Geosmi ...
, which provoked a decline of walnut trees in some regions. Black walnut is anecdotally known for being
allelopathic Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have ben ...
, which means that it releases chemicals from its roots and other tissues that may harm other organisms and give the tree a competitive advantage. There is not, however, solid scientific consensus that allelopathic chemicals in black walnut are the primary source of its competitive growth in an area.


Description

*Odor Most parts of the tree including leaves, stems, and fruit
husk Husk (or hull) in botany is the outer shell or coating of a seed. In the United States, the term husk often refers to the leafy outer covering of an ear of maize (corn) as it grows on the plant. Literally, a husk or hull includes the protective ...
s have a very characteristic pungent or spicy odor. This odor is lacking in the nut itself. *Trunk Height . Under forest competition, it develops a tall and straight trunk. When grown in an open area it has a short trunk and broad crown. *Bark The bark is typically grey-black and deeply furrowed into thin ridges that gives the bark a diamond shaped pattern. *Pith The
pith Pith, or medulla, is a tissue in the stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other ...
of the twigs is chambered and light brown. *Buds The
bud In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be spec ...
s are pale silky and covered in downy hairs. The terminal buds are ovate, and long, and slightly longer than broad, the lateral buds are smaller and superposed. *Leaves The leaves are pinnately
compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive struct ...
and alternately arranged on the stem. They are long, typically even-pinnate but there is heavy variation among leaves. The stems have 15–23 leaflets, when terminal leaf is included, with the largest leaflets located in the center, long and broad. The leaflets have a rounded base and a long pointed (
acuminate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular o ...
) tip as well as having a
serrated Serration is a saw-like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with the material being cut. By having less contact area than a smooth blade or other edge, the applied p ...
edge. The leaves are overall dark green in color and are typically hairy on the underside. *Leaf scar The
leaf scar A leaf scar is the mark left by a leaf after it falls off the twig. It marks the site where the petiole attached to the stem. A leaf scar is typically found below a branch as branches come from axillary buds located above leaf scars. Formation Le ...
has three prominent bundle scars and has a notch on the side that points toward the tip of the branch (distal side) *Flowers Black walnut is
monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...
. The male (
staminate The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...
) flowers are in drooping
catkins A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind-pollinated (anemophilous) but sometimes insect-pollinated (as in ''Salix''). They contain many, usually unisexual flowers, arranged cl ...
long. These are borne from axillary buds on the previous year's growth. The female (
pistillate Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils'' ...
) flowers are terminal, in clusters of two to five on the current year's growth. *Fruit Ripens during the summer/autumn into a spherical fruit (nut) with a brownish-green, semifleshy husk and a brown, corrugated nut. The whole fruit, including the husk falls in October; the seed is relatively small and very hard. The fruit production tends to occur irregularly with some years producing larger crops than others (see
mast year Mast is the fruit of forest trees and shrubs, such as acorns and other nuts. The term derives from the Old English ''mæst'', meaning the nuts of forest trees that have accumulated on the ground, especially those used historically for fattening ...
). Fruiting may begin when the tree is 4–6 years old, but large crops take 20 years. Total lifespan of ''J. nigra'' is about 130 years. Like other trees of the order
Fagales The Fagales are an order of flowering plants, including some of the best-known trees. The order name is derived from genus ''Fagus'', beeches. They belong among the rosid group of dicotyledons. The families and genera currently included are a ...
, such as oaks, hickories, chestnuts, and birches, it is monoecious, with wind-pollinated catkins. Male and female flowers are in separate
spikes The SPIKES protocol is a method used in clinical medicine to break bad news to patients and families. As receiving bad news can cause distress and anxiety, clinicians need to deliver the news carefully. By using the SPIKES method for introducing a ...
, and the female flowers typically appear before the male on a single tree (
dichogamy Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...
). As a consequence,
self-pollination Self-pollination is a form of pollination in which pollen from the same plant arrives at the Stigma (botany), stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). There are two types of self-pollination: in autogamy, pollen i ...
is unlikely. However, individual trees are commonly self-compatible; if they are not pollinated by neighboring trees, they may set self-fertilized seeds. For maximum seed germination, the seeds should be cold-moist stratified for 3–4 months, although the exact time depends on the seed source. The seedlings emerge in April or May. While most trees with taproots have a reputation for slow growth, black walnut is an exception and can achieve very rapid growth in the seedling stage, typically their first year and even more in the second year. Black walnut will not leaf out until temperatures have warmed sufficiently. Leafout in spring is initiated when daytime highs reach approximately 70 °F (21 °C) and leaf drop in fall when daytime highs fall below 65 °F (15 °C). As such, the exact timing will vary in different regions of the US and depending on the weather conditions from year to year, leafout is typically early April in the southern part of its range and sometimes not until the end of May or beginning of June in cooler areas. Leaf drop in fall may begin in late September in cooler regions and not until November in southern areas. Black walnut has a strong
taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plants, such as the carrot, the taproo ...
, which makes the seedlings resilient, but difficult to transplant. Black walnut is more resistant to frost than the
English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ide ...
or
Persian walnut ''Juglans regia'', the Persian walnut, English walnut, Carpathian walnut, Madeira walnut, or especially in Great Britain, common walnut, is an Old World walnut tree species native to the region stretching from the Balkans eastward to the Himala ...
, but thrives best in the warmer regions of fertile, lowland soils with high water tables, although it will also grow in drier soils, but much more slowly. Some soils preferred by black walnut include
Alfisol Alfisols are a soil order in USDA soil taxonomy. Alfisols form in semi-arid to humid areas, typically under a hardwood forest cover. They have a clay-enriched subsoil and relatively high native fertility. "Alf" refers to aluminium (Al) and iron ( ...
and
Entisol Entisols are soils defined in USDA soil taxonomy that do not show any profile development other than an A horizon. An entisol has no diagnostic horizons, and most are basically unaltered from their parent material, which can be unconsolidated sedi ...
soil types. Black walnut grows best on sandy loam, loam, or silt loam type soils but will also grow well on silty clay loam soils. It prefers these soils because they hold large quantities of water, which the tree draws from during rainless periods. Visually, black walnut is similar to the butternut (''Juglans cinerea'') in leaf shape, and the range also overlaps significantly. The fruits are quite different, and their presence makes an identification easy, as black walnut fruits are round (spherical) and butternuts are more oval-oblong shaped. When a fruit is not available, two species can be differentiated based on the
leaf scar A leaf scar is the mark left by a leaf after it falls off the twig. It marks the site where the petiole attached to the stem. A leaf scar is typically found below a branch as branches come from axillary buds located above leaf scars. Formation Le ...
s, or the place where the leaf meets the stem: butternut has a leaf scar with a flat upper edge and with a velvety ridge above that flat part, but black walnut has an indented leaf scar with no hairy ridge.


Ecology

Black walnut is primarily a
pioneer species Pioneer species are hardy species that are the first to colonize barren environments or previously biodiverse steady-state ecosystems that have been disrupted, such as by wildfire. Pioneer flora Some lichens grow on rocks without soil, so m ...
similar to
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...
and
silver maple ''Acer saccharinum'', commonly known as silver maple, creek maple, silverleaf maple, soft maple, large maple, water maple, swamp maple, or white maple, is a species of maple native to the eastern and central United States and southeastern Canad ...
and
black cherry ''Prunus serotina'', commonly called black cherry,World Economic Plants: A Standard Reference, Second Edition'. CRC Press; 19 April 2016. . p. 833–. wild black cherry, rum cherry, or mountain black cherry, is a deciduous tree or shrub of the ...
. Because of this, black walnut is a common weed tree found along roadsides, fields, and forest edges in the eastern US. It will grow in closed forests, but is classified as shade intolerant; this means it requires full sun for optimal growth and nut production. Black walnut's native range extends across much of the eastern US. It is absent from the coastal plain south of
North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...
as well as the Mississippi Valley, and does not occur in the northern tier of the eastern US, where the frost-free season is too short for the nuts to develop. Its western range extends all the way to the eastern Great Plains, after which climate conditions become too dry for it. Black walnut is one of the most abundant trees in the eastern US, particularly the Northeast, and its numbers are increasing due to epidemics that have affected other tree species, including emerald ash borer, chestnut blight, butternut canker, wooly hemlock adelgid, dogwood anthracnose, Dutch elm disease, and Gypsy moth infestations. Widespread clear-cutting of oaks due to Gypsy moth damage in the 1970s-80s particularly aided in the tree's spread. The aggressive competitive strategy of black walnut such as its fast growth, alleopathic chemicals, and rodent-dispersed seeds, have also contributed. The nuts are food for many rodents and make up to 10% of the diet of
eastern fox squirrel The fox squirrel (''Sciurus niger''), also known as the eastern fox squirrel or Bryant's fox squirrel, is the largest species of tree squirrel native to North America. Despite the differences in size and coloration, it is sometimes mistaken for ...
s. The nuts are also eaten by species of birds. The leaves are browsed by
white tailed deer The white-tailed deer (''Odocoileus virginianus''), also known as the whitetail or Virginia deer, is a medium-sized deer native to North America, Central America, and South America as far south as Peru and Bolivia. It has also been introduced t ...
, although they are not a preferred food. Squirrels also eat the nuts. Where the range of the eastern black walnut overlaps that of the Texas black walnut ('' J. microcarpa''), the two species sometimes interbreed, producing populations with characteristics intermediate between the two species. ''J.nigra'' and ''J. cinerea'' often grow in the same range as well but they do not hybridize naturally. The tree's roots often form
endomycorrhiza   A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plan ...
l relationships with fungi in the genus ''Glomus''. Some endomycorrhizal relations improve the plant's growth. Species often associated with ''J. nigra'' include
yellow-poplar ''Liriodendron tulipifera''—known as the tulip tree, American tulip tree, tulipwood, tuliptree, tulip poplar, whitewood, fiddletree, and yellow-poplar—is the North American representative of the two-species genus ''Liriodendron'' (the other ...
(''Liriodendron tulipifera''), white ash (''Fraxinus americana''),
black cherry ''Prunus serotina'', commonly called black cherry,World Economic Plants: A Standard Reference, Second Edition'. CRC Press; 19 April 2016. . p. 833–. wild black cherry, rum cherry, or mountain black cherry, is a deciduous tree or shrub of the ...
(''Prunus serotina''),
basswood ''Tilia americana'' is a species of tree in the family Malvaceae, native to eastern North America, from southeast Manitoba east to New Brunswick, southwest to northeast Oklahoma, southeast to South Carolina, and west along the Niobrara River to ...
(''Tilia americana''), American beech (''Fagus grandifolia''),
sugar maple ''Acer saccharum'', the sugar maple, is a species of flowering plant in the soapberry and lychee family Sapindaceae. It is native to the hardwood forests of eastern Canada and eastern United States. Sugar maple is best known for being the prima ...
(''Acer saccharum''),
oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
s (''Quercus'' spp.), and hickories (''Carya'' spp.). Near the western edge of its range, black walnut may be confined to floodplains, where it grows either with
American elm ''Ulmus americana'', generally known as the American elm or, less commonly, as the white elm or water elm, is a species of elm native to eastern North America, naturally occurring from Nova Scotia west to Alberta and Montana, and south to Flor ...
(''Ulmus americana''), common hackberry (''Celtis occidentalis''),
green ash ''Fraxinus pennsylvanica'', the green ash or red ash, is a species of ash native to eastern and central North America, from Nova Scotia west to southeastern Alberta and eastern Colorado, south to northern Florida, and southwest to Oklahoma and e ...
(''Fraxinus pennsylvanica''), and
boxelder ''Acer negundo'', the box elder, boxelder maple, Manitoba maple or ash-leaved maple, is a species of maple native to North America. It is a fast-growing, short-lived tree with opposite, compound leaves. It is sometimes considered a weedy or inv ...
(''Acer negundo''), or with basswood and
red oak The genus Oak, ''Quercus'' contains about 500 species, some of which are listed here. The genus, as is the case with many List of the largest genera of flowering plants, large genera, is Taxonomic rank#Ranks in botany, divided into subgenus, subgen ...
(''Quercus rubra'') on lower slopes and other favorable sites.


Cultivation


Planting

While its primary native region is the Midwest and east-central United States, the black walnut was introduced into Europe in 1629 and is also cultivated in Hawaii. It is cultivated there and in North America as a forest tree for its high-quality wood. Black walnut plantings can be made to produce timber, nuts, or both timber and nuts. Patented timber-type trees were selected and released from
Purdue University Purdue University is a public land-grant research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and money ...
in the early 1990s. These trees have been sporadically available from nurseries. Varieties include Purdue #1, which can be used for both timber and nut production, though nut quality is poor compared to varieties selected specifically as nut producers.
Grafted Grafting or graftage is a horticultural technique whereby tissues of plants are joined so as to continue their growth together. The upper part of the combined plant is called the scion () while the lower part is called the rootstock. The succ ...
, nut-producing trees are available from several nurseries operating in the U.S. Selections worth considering include Thomas, Neel #1, Thomas Myers, Pounds #2, Stoker, Surprise, Emma K, Sparrow, S127, and McGinnis. Several older varieties, such as Kwik Krop, are still in cultivation; while they make decent nuts, they would not be recommended for commercial planting. Pollination requirements should be considered when planting black walnuts. As is typical of many species in Juglandaceae, ''Juglans nigra'' trees tend to be monoecious, i.e.. produce
pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
first and then pistillate flowers or else produce pistillate flowers and then pollen. An early pollen-producer should be grouped with other varieties that produce pistillate flowers so all varieties benefit from overlap. Cranz, Thomas, and Neel #1 make a good pollination trio. A similar group for more northern climates would be Sparrow, S127, and Mintle. Sometimes black walnut is planted as part of reclaiming mines. When growing young trees weed control is critical for healthy establishment of the trees, without weed control the young trees are harmed significantly in their growth rate.


Ornamental

''J. nigra'' is also grown as a specimen ornamental tree in parks and large gardens, growing to tall by broad. It has gained the
Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr (Nort ...
's
Award of Garden Merit The Award of Garden Merit (AGM) is a long-established annual award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. History The Award of Garden Merit ...
.


Uses


As food

150px, A bowl of black walnut kernels, shelled Black walnut nuts are edible and shelled commercially in the United States. About 65% of the annual wild harvest comes from the U.S. state of
Missouri Missouri is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it is bordered by eight states (tied for the most with Tennessee ...
, and the largest processing plant is operated by Hammons Products in
Stockton, Missouri Stockton is a city in Cedar County, Missouri, United States. The population was 1,683 at the 2020 census. It is the county seat of Cedar County. History Stockton was platted in 1846. It was originally named Lancaster, but was renamed Fremont in 1 ...
.
NPR National Public Radio (NPR, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from other ...
affiliate KCUR stated in an article that “Ralph Hammons began the company in 1946 with a nut cracking machine acquired from Tennessee.” The Stockton ''Black Walnut Festival'', which has been held annually since 1961, “brings the community together for a 3-day event jam-packed with activities including a carnival, tractor pull, nut roll and 2-hour parade,” stated Alexa Hodges in a VOX article. The nutmeats provide a robust, distinctive, natural flavor and crunch as a food ingredient. Popular uses include ice cream, bakery goods and confections. Consumers include black walnuts in traditional treats, such as
cake Cake is a flour confection made from flour, sugar, and other ingredients, and is usually baked. In their oldest forms, cakes were modifications of bread, but cakes now cover a wide range of preparations that can be simple or elaborate, ...
s,
cookie A cookie is a baked or cooked snack or dessert that is typically small, flat and sweet. It usually contains flour, sugar, egg, and some type of oil, fat, or butter. It may include other ingredients such as raisins, oats, chocolate chips, n ...
s,
fudge Fudge is a type of confection that is made by mixing sugar, butter and milk, heating it to the soft-ball stage at , and then beating the mixture while it cools so that it acquires a smooth, creamy consistency. In texture, this crystalline cand ...
, and
pie A pie is a baked dish which is usually made of a pastry dough casing that contains a filling of various sweet or savoury ingredients. Sweet pies may be filled with fruit (as in an apple pie), nuts ( pecan pie), brown sugar ( sugar pie), swe ...
s, during the fall holiday season. The nuts' nutritional profile leads to uses in other foods, such as
salad A salad is a dish consisting of mixed, mostly natural ingredients with at least one raw ingredient. They are typically served at room temperature or chilled, though some can be served warm. Condiments and salad dressings, which exist in a va ...
s,
fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
,
pork Pork is the culinary name for the meat of the domestic pig (''Sus domesticus''). It is the most commonly consumed meat worldwide, with evidence of pig husbandry dating back to 5000 BCE. Pork is eaten both freshly cooked and preserved; ...
,
chicken The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adult m ...
, vegetables and pasta dishes. Tapped in spring, the tree yields a sweet sap that can be drunk or concentrated into syrup or sugar that is not unlike the sap of
sugar maple ''Acer saccharum'', the sugar maple, is a species of flowering plant in the soapberry and lychee family Sapindaceae. It is native to the hardwood forests of eastern Canada and eastern United States. Sugar maple is best known for being the prima ...
.


Nut processing by hand

The extraction of the kernel from the fruit of the black walnut is difficult. The thick, hard shell is tightly bound by tall ridges to a thick husk. Rolling the nut underfoot on a hard surface such as a driveway is a common method; commercial huskers use a car tire rotating against a metal mesh. Some take a thick plywood board and drill a nut-sized hole in it (from one to two inches in diameter) and smash the nut through using a hammer. The nut goes through and the husk remains behind. American pioneers let the nuts dry in the sun, then removed the husks and let the kernels dry—making them less bitter. The shell itself is thicker than that of the English walnut, and there are additional, thick internal walls tightly surrounding the nutmeat. Walnuts are too tough and too large to be opened with a standard nutcracker, but simply cracking the shell open with a rock results in smashed and shattered nutmeats mixed with shell, unless done with some care and skill—and it is still nearly impossible to extract an intact half this way. As a result, a number of home walnut-cracking devices have been produced, involving vices, cams, or levers. While the flavor of the ''Juglans nigra'' kernel is prized, the difficulty in preparing it may account for the wider popularity and availability of the English walnut.


Nutrition

Black walnut kernels are 5% water, 59%
fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...
, 24%
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
, and 10%
carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...
s (table). In a 100 gram reference amount providing 619
calorie The calorie is a unit of energy. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie was originally defined as the amount of heat needed to raise the temperature of on ...
s, the kernels supply several
dietary minerals In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon, ...
in rich content (20% or more of the
Daily Value The Reference Daily Intake (RDI) used in nutrition labeling on food and dietary supplement products in the U.S. and Canada is the daily intake level of a nutrient that is considered to be sufficient to meet the requirements of 97–98% of health ...
, DV), including
manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
(186% DV) and
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
(73% DV) among others, and the
B vitamins B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. Though these vitamins share similar names (B1, B2, B3, etc.), they are chemically distinct compounds that often coexist ...
, B6 (45% DV) and
pantothenic acid Pantothenic acid, also called vitamin B5 is a water-soluble B vitamin and therefore an essential nutrient. All animals require pantothenic acid in order to synthesize coenzyme A (CoA) – essential for fatty acid metabolism – as well as to, i ...
(33% DV) (table). Black walnut kernels are a moderate source of
vitamin E Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vitami ...
(14% DV). Analysis of black walnut fat content in its oil showed the most prevalent
fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...
s are
linoleic acid Linoleic acid (LA) is an organic compound with the formula COOH(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are cis-trans isomerism, ''cis''. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 ''cis''-9,12. A linoleate is a salt (chem ...
(33.8%), followed (in the same units) by
oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega ...
(15.3%),
linolenic acid Linolenic acid is a type of naturally-occurring fatty acid. It can refer to either of two octadecatrienoic acids (i.e. with an 18-carbon chain and three double bonds, which are found in the '' cis'' configuration), or a mixture of the two. Lino ...
(2.7%),
palmitic acid Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and microorganisms.Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The Li ...
(1.9%), and
stearic acid Stearic acid ( , ) is a saturated fatty acid with an 18-carbon chain. The IUPAC name is octadecanoic acid. It is a waxy solid and its chemical formula is C17H35CO2H. Its name comes from the Greek word στέαρ "''stéar''", which means tallow. ...
(1.5%) (USDA table).


Dye

Black walnut
drupes In botany, a drupe (or stone fruit) is an indehiscent fruit in which an outer fleshy part (exocarp, or skin, and mesocarp, or flesh) surrounds a single shell (the ''pit'', ''stone'', or '' pyrena'') of hardened endocarp with a seed (''kernel'') ...
contain
juglone Juglone, also called 5-hydroxy-1,4-naphthalenedione (IUPAC) is an organic compound with the molecular formula C10H6O3. In the food industry, juglone is also known as C.I. Natural Brown 7 and C.I. 75500. It is insoluble in benzene but soluble i ...
(5-hydroxy-1,4-naphthoquinone),
plumbagin Plumbagin or 5-hydroxy-2-methyl-1,4-naphthoquinone is an organic compound with the chemical formula . It is regarded as a toxin and it is genotoxic and mutagenic. Plumbagin is a yellow dye,tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...
. These compounds cause walnuts to stain cars, sidewalks, porches, and patios, in addition to the hands of anyone attempting to shell them. The brownish-black dye was used by early American settlers to dye hair. According to Eastern Trees in the Petersen Guide series, black walnuts make a yellowish-brown dye, not brownish-black. The apparent confusion is easily explained by the fact that the liquid (dye) obtained from the inner husk becomes increasingly darker over time, as the outer skin darkens from light green to black. Extracts of the outer, soft part of the drupe are still used as a
natural dye Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources—roots, berries, bark, leaves, and wood—and other biological sources such as fungi. Archa ...
for handicrafts. The tannins present in walnuts act as a
mordant A mordant or dye fixative is a substance used to set (i.e. bind) dyes on fabrics by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying stains in ...
, aiding in the dyeing process, and are usable as a dark ink or wood stain.


Industrial

Walnut shells are often used as an abrasive in sand blasting or other circumstances where a medium hardness grit is required. The hard black walnut shell is also used commercially in abrasive cleaning, a filtering agent in scrubbers in smoke stacks, cleaning jet engines, cosmetics, and oil well drilling and water filtration.


Wood

Black walnut is highly prized for its dark-colored, straight grained, true heartwood. It is heavy, strong, shock resistant and yet can be easily split and worked. Along with cedars ( ''Thuja spp.''), chestnut ( ''Castanea spp''.), and black locust (''
Robinia pseudoacacia ''Robinia pseudoacacia'', commonly known in its native territory as black locust, is a medium-sized hardwood deciduous tree, belonging to the tribe Robinieae of the legume family Fabaceae. It is endemic to a few small areas of the United States, ...
'') black walnut is one of the most durable hardwoods in the US. The wood can be kiln dried and holds its shape well after seasoning, which makes this wood even more attractive for wood working. Walnut wood has historically been used for
gun stock A gunstock or often simply stock, the back portion of which is also known as a shoulder stock, a buttstock or simply a butt, is a part of a long gun that provides structural support, to which the barrel, action, and firing mechanism are attach ...
s, furniture, flooring, paddles, coffins, and a variety of other wood products. Due to its value, forestry officials often are called on to track down walnut poachers; in 2004, DNA testing was used to solve one such poaching case, involving a 55-foot (16-m) tree worth
US$ The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
2,500. Black walnut has a density of 660 kg per cubic meter (41.2 lb/cubic foot), which makes it less dense than oak.


Pests

Maggot A maggot is the larva of a fly (order Diptera); it is applied in particular to the larvae of Brachycera flies, such as houseflies, cheese flies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and crane flies. ...
s (larvae of '' Rhagoletis completa'' and '' Rhagoletis suavis'') in the husk are common, though more a nuisance than a serious problem for amateurs, who may simply remove the affected husk as soon as infestation is noticed. The maggots develop entirely within the husk, thus the quality of the nutmeat is not affected. However, infestations of maggots are undesirable because they make the husk difficult to remove and are unsightly. Maggots can be serious for commercial walnut growers, who tend to use chemical treatments to prevent damage to the crop. Some non-chemical controls also exist, such as removing and disposing of infested nuts. The walnut
weevil Weevils are beetles belonging to the Taxonomic rank, superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and Herbivore, herbivorous. Approximately 97,000 species of weevils are known. They b ...
('' Conotrachelus retentus'') grows to long as an adult. The adult sucks plant juices through a snout. The eggs are laid in fruits in the spring and summer. Many nuts are lost due to damage from the larvae, which burrow through the nut shell. Black walnut is affected by European canker (''
Neonectria galligena ''Neonectria ditissima'' (syn. ''Neonectria galligena'') is a fungal plant pathogen. It causes cankers that can kill branches of trees by choking them off. Apple and beech trees are two susceptible species. Host range ''Neonectria ditissima ...
''). The infection spreads slowly but infected trees eventually die. The walnut caterpillar (''
Datana integerrima ''Datana integerrima'', the walnut caterpillar moth, is a moth of the family Notodontidae. It is found in eastern North America, from Ontario, through most of the Eastern States west to Minnesota and south to northern Mexico. The wingspan is 3 ...
'') and fall webworm ('' Hyphantria cunea'') are two of the most serious pests, they commonly eat the foliage in midsummer and continue into autumn. Codling moth (''
Cydia pomonella The codling moth (''Cydia pomonella'') is a member of the Lepidopteran family Tortricidae. They are major pests to agricultural crops, mainly fruits such as apples and pears. Because the larvae are not able to feed on leaves, they are highly dep ...
'') larvae eat walnut kernels, as well as apple and pear seeds. Important leaf sucking insects include species of
aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s and plant lice including ('' Monellia'' spp. and '' Monelliopsis'' spp.), which suck the juices from leaves and often deposit a sticky substance called "honey-dew" on the leaf surface that may turn black and prevent photosynthesis; and the walnut lace bug ('' Corythucha juglandis''), which causes damage when the adults and nymphs suck the sap from the lower surfaces of walnut leaflets. A disease complex known as
thousand cankers disease Thousand cankers disease (TCD) is a recently recognized disease of certain walnuts (''Juglans'' spp.). The disease results from the combined activity of the walnut twig beetle (''Pityophthorus juglandis'') and a canker producing fungus, '' Geosmi ...
has been threatening black walnut in several western states. This disease has recently been discovered in Tennessee, and could potentially have devastating effects on the species in the eastern United States. Vectored by the walnut twig beetle ('' Pityophthorus juglandis''), a fungus, '' Geosmithia morbida'', spreads into the wood around the galleries carved by the small beetles. The fungus causes cankers that inhibit the movement of nutrients in black walnut, leading to crown and branch dieback, and ultimately death.


Allelopathy

While black walnut is considered
allelopathic Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have ben ...
, meaning it excretes chemicals into its environment that harm competition, research over the past decade has questioned whether this long-held belief holds up to scientifically rigorous examination. Many publications that have repeated claims of black walnut allelopathy cite a very limited set of dated research literature, which has not held up to scientific scrutiny. Anecdotally, records of walnut toxicity to other plants have been observed as far back as the first century when
Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...
wrote: "The shadow of walnut trees is poison to all plants within its compass." Like other
walnut A walnut is the edible seed of a drupe of any tree of the genus ''Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. Although culinarily considered a "nut" and used as such, it is not a true ...
s, the roots, inner bark, nut husks, and leaves contain a nontoxic chemical called hydrojuglone, when exposed to air or soil compounds it is oxidized into
juglone Juglone, also called 5-hydroxy-1,4-naphthalenedione (IUPAC) is an organic compound with the molecular formula C10H6O3. In the food industry, juglone is also known as C.I. Natural Brown 7 and C.I. 75500. It is insoluble in benzene but soluble i ...
that is biologically active and acts as a respiratory inhibitor to some plants. Juglone is poorly soluble in water and does not move far in the soil and will stay most concentrated in the soil directly beneath the tree. Even after a tree is removed the soil where the roots once were will still contain juglone for several years after the tree is removed as more juglone will be released as the roots decay. Well drained and aerated soils will host a healthy community of soil microbes and these microbes will help to break down the juglone. Symptoms of juglone poisoning include foliar yellowing and wilting. A number of plants are particularly sensitive. Apples, tomatoes, pines, and birch are poisoned by juglone, and as a precaution, should not be planted in proximity to a black walnut.


Interaction with horses

Horses are susceptible to
laminitis Laminitis is a disease that affects the feet of ungulates and is found mostly in horses and cattle. Clinical signs include foot tenderness progressing to inability to walk, increased digital pulses, and increased temperature in the hooves. Sever ...
from exposure to black walnut wood in bedding.


Largest trees

The US national champion black walnut is on a residential property on
Sauvie Island Sauvie Island, in the U.S. state of Oregon, originally Wapato Island or Wappatoo Island, is the largest island along the Columbia River, at , and one of the largest river islands in the United States. It lies approximately ten miles northwest of ...
,
Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
. It is
diameter at breast height Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bole of a standing tree. DBH is one of the most common dendrometric measurements. Tree trunks are measured at the height of an adult's breast, ...
and tall, with a crown spread of . The tallest black walnut in Europe is located in the Woluwe Park in the city of Sint-Pieters-Woluwe, Brussels, Belgium. It has a circumference of , height of exactly (measured by laser), and was planted around 1850 (± 10 years). The largest black walnut in Europe is located in the Castle Park in the city of
Sereď Sereď (; hu, Szered ) is a town in southern Slovakia near Trnava, on the right bank of the Váh River on the Danubian Lowland. It has approximately 15,500 inhabitants. Geography Sereď lies at an altitude of above sea level and covers an are ...
,
Slovakia Slovakia (; sk, Slovensko ), officially the Slovak Republic ( sk, Slovenská republika, links=no ), is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the s ...
. It has a circumference of , height of and estimated age of 300 years.


See also

* English walnut, Persian walnut * Taxonomy of walnut tree varieties *
Anthelmintic Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms (helminths) and other internal parasites from the body by either stunning or killing them and without causing significant damage to the host. They may a ...


References


Further reading

* *Petrides, G. A. and Wehr, J. (1998). ''Eastern Trees''. Houghton Mifflin Company. *Little, Elbert L. (1980) ''National Audubon Society Field Guide to North American Trees: Eastern Edition.'' Borzoi Books.


External links

*A variety index and characteristics guide is available fro
Missouri Extension

Guide to "Growing Black Walnuts for Nut Production"
University of Missouri Center for Agroforestry *
Walnut Council.org homepageFlora of North America: ''Juglans nigra''

Range distribution Map:Set of Black Walnut ID photos and range map''Juglans nigra''
- information, genetic conservation units and related resources.
European Forest Genetic Resources Programme European Forest Genetic Resources Programme (EUFORGEN) is an international network that supports the conservation and sustainable use of forest genetic resources in Europe. The programme’s tasks include to coordinate and promote '' in situ'' an ...
(EUFORGEN) {{Authority control nigra Edible nuts and seeds Trees of Eastern Canada Trees of the Eastern United States Trees of the Great Lakes region (North America) Trees of the Northeastern United States Trees of the North-Central United States Trees of the Plains-Midwest (United States) Trees of the Southeastern United States Walnut, Black Flora of the Appalachian Mountains Symbols of Missouri Trees of humid continental climate Plants described in 1753 Taxa named by Carl Linnaeus Plant dyes Garden plants of North America Ornamental trees Flora of Texas Trees of the Southern United States Trees of North America Trees of the United States Trees of Canada Trees of the South-Central United States