Juglans nigra, black walnut
Coladonato, Milo. 1991. Juglans nigra, black walnut. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/jugnig
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| JUGNIG | black walnut | Juglans nigra | Life Form: Plants/Tree Kingdom: Plantae Class: Dicot Order: Juglandales Family: Juglandaceae Genus: Juglans | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Taxonomy
The currently accepted scientific name for black walnut is Juglans nigra L. [21]. There are no recognized subspecies, varieties, or forms. Black walnut and butternut (J. cinerea) often grow together but apparently never cross naturally [43].
Synonyms
- None
Other Common Names
walnut, eastern black walnut, American walnut
General Distribution
Black walnut is found throughout the eastern United States. It grows as far north as southern Minnesota, southern Wisconsin, southern Michigan, and southern Ontario. Isolated populations occur in the southern half of New York, Vermont, western Massachusetts, and northwestern Connecticut. Its range extends south to northwestern Florida, and to Mississippi, Arkansas, and Louisiana except for the Mississippi Valley and Delta regions. In the Midwest, isolated populations occur in eastern Texas, western Oklahoma, central Kansas, and southeastern South Dakota [8,29,30]. Black walnut is cultivated in Hawaii [45].
States and Provinces
- United States: AL AR CT DE FL GA HI IA IL IN KS KY LA MA MD MI MN MO MS NC NE NJ NY OH OK PA SC SD TN TX VA VT WI WV
- Canada: ON
Site Characteristics
Black walnut is found on a variety of sites but grows best on deep, well-drained neutral soils that are moist and fertile [43]. It grows slowly on wet bottomlands, dry ridges, and slopes. Black walnut is common on limestone soils [9,10] and grows extremely well on deep loams and fertile alluvial deposits. Good agricultural soils are generally favorable sites for black walnut. In the Appalachians, the best walnut trees are found on bottomlands and coves below 4,000 feet (1,200 m) [5].
Principal associates are identified in Table A1. Other common tree associates include American elm (Ulmus americana), hackberry (Celtis laevigata), green ash (Fraxinus pennsylvanica), box elder (Acer negundo), and butternut (Juglans cinerea) [29].
Plant Communities
No entry.
Botanical Description
Black walnut is a native, deciduous tree that can grow to a height of 125 feet (38 m) but ordinarily grows to around 80 feet (25 m) [10,43]. Black walnut develops a long, smooth trunk and a small, rounded crown when growing in the forest. In the open, the trunk forks low with a few ascending and spreading coarse branches. The root system usually consists of a deep taproot and several wide-spreading lateral roots. The bark on young trees is dark and scaly but becomes darker with rounded intersecting ridges on mature trees [17,39].
Raunkiaer Life Form (Raunkiaer 1934)
- Phanerophyte
Seasonal Development
Black walnut normally begins flowering about mid-April in the southern part of its geographic range and mid-June in the northern part of its range. The fruit ripens in September or October of the same year, dropping shortly after the leaves fall [10,29].
Regeneration Processes
Black walnut with fruits.
Seed production
Black walnut produces abundant seed crops irregularly, perhaps twice in 5 years. Although open-grown trees produce seed as early as 8 years after planting, the minimum seed-bearing age for commercial quantities of seed is about 12 years. Best seed production begins when the tree is about 30 years old and continues for another 100 years [31,43].
Dispersal
Black walnut seed is heavy. The seeds are dispersed by squirrels carrying seed from beneath the tree and burying them at a distance [29,36].
Seedling development
Many black walnut seedlings germinate from the nuts cached by squirrels in the fall. Normal freezing and thawing usually causes the seeds to break dormancy the following spring, but germination is often delayed, sometimes until the second year [3,35].
Vegetative reproduction
Small black walnut trees usually sprout from the stump when they are cut or killed back by fire. Shoots originating high on the older stumps often decay, but shoots from the root crown generally are free from defect [22,43].
Successional Status
Black walnut is classified as shade intolerant. In mixed forest stands, it must be dominant to survive, although it can survive in the relatively light shade of black locust [43]. Black walnut is found in many of the climax associations but because of its intolerance is not classified as a climax tree in the strict sense. In general, black walnut maintains itself in most stands as scattered single trees occupying openings in the canopy [15].
Immediate Fire Effects
Young black walnut trees are typically top-killed by most fires [18,31].
Postfire Regeneration Strategy (Stickney 1989)
- survivor species; on-site surviving root crown or caudex
- off-site colonizer; seed carried by animals or water; postfire yr 1&2
Fire Adaptations
Black walnut is well adapted to fire. Mature trees have thick bark and naturally durable heartwood which make them relatively resistant to damage and decay following fire [32,34,43].
Plant Response to Fire
Small 20- to 30-year-old black walnut trees will usually sprout from the root collar or stump when top-killed by fire. Sprouting is more erratic from trees 30 years and older [31,43].
Fire Regimes
For fire regime information, search FEIS for this species by entering the species name or acronym on the home page and selecting “Fire Regime” as the publication type.
Fire Management Considerations
Where the danger of fire exists, fuel buildup in young black walnut plantations should be reduced by removing grasses and weeds [1,31,42].
Federal Status
None
Other Status
No entry.
Importance to Wildlife and Livestock
The nuts of black walnut furnish food for many rodents and make up about 10 percent of the diet of eastern fox squirrels [19,33]. The nuts are also eaten by a variety of birds [2].
Palatability and Nutritional Value
Although not considered a choice browse, black walnut leaves are palatable to white-tailed deer [16].
Nutrient percentages (dry basis) for the nuts of black walnut are as follows [41]:
| Crude protein | 29.25 |
|---|---|
| Ether | 60.25 |
| Crude fiber | 1.03 |
| Ash | 2.76 |
| N-free extract | 6.73 |
| Available protein | 27.06 |
| Lignin | 0.87 |
| Cellulose | 2.01 |
| Tannin | 0.25 |
| Calcium | 0.01 |
| Magnesium | 0.27 |
| Phosphorus | 0.59 |
Cover Value
The eastern screech-owl roosts on the limbs of black walnut [6].
Value for Rehabilitation or Restoration of Disturbed Sites
Black walnut has been successfully planted on surface mined areas in the eastern United States [4,7]. In southwestern Indiana, black walnut had a 30 to 50 percent increase in survival rate on old mine field sites where weed competition had been chemically controlled or removed [4].
Other Uses
The nuts of black walnut are used as food by humans and are harvested commercially [26]. The nuts are eaten plain or with honey and used to flavor cakes, candy, and ice cream [14]. Native Americans used the nuts for food and extracted black dye from the roots. The black walnut is mentioned in Native American creation myths [14]. Black walnut is cultivated as an ornamental [40].
The ground shells of black walnut are used as a nonslip agent in automobile tires, as an air pressure propellant in strip paints, and as a filtering agent for scrubbers in smoke stacks. The automobile industry uses the ground shell products to deburr precision gears, and the airline industry uses the ground shells to clean jet engines [43].
Wood Products Value: Black walnut wood is heavy, strong, and highly resistant to shock. It ranks with the most durable U.S. hardwoods, including cedars (Thuja spp.), chestnuts (Castanea spp.), and black locust (Robinia pseudoacacia). It can be satisfactorily kiln dried and holds it shape well after seasoning. Black walnut is normally straight grained, is worked easily with hand tools, and has excellent machining properties. When finished, the wood takes on a smooth velvety surface and a handsome grain pattern [25,29].
Black walnut is used principally for dining room and bedroom furniture; bookcases; desks; tables; radio, television, phonograph, and piano cabinets; and as an interior finish in cafes and public buildings [24]. The veneer is used for the highest grade cabinets and plywood panels. Figured black walnut stocks are prized for expensive shotguns and sporting rifles [8,29].
Other Management Considerations
Weed control is essential for the establishment of black walnut on sites suitable for intensive culture [31].
An antagonism between black walnut and many other plants growing within its root zone has been recognized and attributed to juglone, a toxic substance found in the leaves, bark, nut husks, and roots of black walnut trees. Many garden vegetables and several conifers are susceptible to juglone [12,17,28].
Black walnut is particularly susceptible to European canker (Nectria galligena). The infection spreads quite slowly, but infected trees eventually die [29,43].
Black alder (Alnus glutinosa) and Russian olive (Elaeagnus angustifolia) interplanted with black walnut increases black walnut's yield because of their ability to increase available nitrogen in the soil [37,44].
Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.
Forest and Range Ecosystems (Garrison et al. 1977)
- FRES10 White - red - jack pine
- FRES11 Spruce - fir
- FRES12 Longleaf - slash pine
- FRES13 Loblolly - shortleaf pine
- FRES14 Oak - pine
- FRES15 Oak - hickory
- FRES16 Oak - gum - cypress
- FRES17 Elm - ash - cottonwood
- FRES18 Maple - beech - birch
BLM Physiographic Regions (Bernard and Brown 1977)
- No entry.
Kuchler Plant Associations (Kuchler 1964)
- K089 Black Belt
- K095 Great Lakes pine forest
- K096 Northeastern spruce - fir forest
- K097 Southeastern spruce - fir forest
- K099 Maple - basswood
- K100 Oak - hickory forest
- K101 Elm - ash forest
- K102 Beech - maple forest
- K103 Mixed mesophytic forest
- K104 Appalachian oak forest
- K106 Northern hardwoods
- K107 Northern hardwoods - fir forest
- K108 Northern hardwoods - spruce forest
- K110 Northeastern oak - pine forest
- K111 Oak - hickory - pine forest
- K112 Southern mixed forest
- K113 Southern floodplain forest
- K114 Pocosin
SAF Cover Types (Eyre 1980)
- 14 Northern pin oak
- 18 Paper birch
- 19 Gray birch - red maple
- 21 Eastern white pine
- 22 White pine - hemlock
- 23 Eastern hemlock
- 26 Sugar maple - basswood
- 27 Sugar maple
- 28 Black cherry - maple
- 40 Post oak - blackjack oak
- 42 Bur oak
- 43 Bear oak
- 44 Chestnut oak
- 45 Pitch pine
- 46 Eastern redcedar
- 52 White oak - black oak - northern red oak
- 53 White oak
- 55 Northern red oak
- 57 Yellow-poplar
- 58 Yellow-poplar - eastern hemlock
- 59 Yellow-poplar - white oak - northern red oak
- 60 Beech sugar maple
- 61 River birch - sycamore
- 62 Silver maple - American elm
- 64 Sassafras - persimmon
- 65 Pin oak - sweet gum
- 75 Shortleaf pine
- 76 Shortleaf pine - oak
- 78 Virginia pine - oak
- 79 Virginia pine
- 80 Loblolly pine - shortleaf pine
- 81 Loblolly pine
- 82 Loblolly pine - hardwood
- 91 Swamp chestnut oak - cherrybark oak
- 93 Sugarberry - American elm - green ash
SRM Rangeland Cover Types (Shiflet 1994)
- No entry.
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