Black walnut (Juglans nigra): what the agencies record

This page reports what US federal publications say about one tree. It does not identify trees from descriptions or photos and does not say what should be done with any tree. The family overview, tree species in the agency records, explains the sources and holds the comparison table.

At a glance

Item	What the source records
Scientific name	Juglans nigra L., walnut family
Other names	Eastern black walnut and American walnut (Silvics)
Native status, USDA PLANTS	Native in Canada and in the lower 48 states
Mature size, Silvics	On good sites 30 to 37 m (100 to 120 ft) tall and 76 to 102 cm (30 to 40 in) in diameter
Green weight of the wood, NRS-38	57 lb per cubic foot, without bark

Native range

The Silvics of North America handbook (Agriculture Handbook 654, 1990) calls black walnut one of the scarcest and most coveted native hardwoods and says it typically grows as scattered individual trees or in small groups through the central and eastern United States. It records a natural range from western Vermont and Massachusetts west through New York to southern Ontario, central Michigan, southern Minnesota, eastern South Dakota and northeastern Nebraska, south to western Oklahoma and central Texas, and, excluding the Mississippi River Valley and Delta, east to northwestern Florida and Georgia. The handbook says walnut grows best on good sites in coves and well-drained bottoms in the Appalachians and the Midwest, and that on the western fringe of its range in Kansas it often makes up 50 percent or more of the basal area in stands of several hectares.

Size and growth

Silvics says that on the best sites young trees may grow 91 to 122 cm (36 to 48 in) in height a year. It records trees 40 m (130 ft) tall and more than 244 cm (96 in) in diameter in Wisconsin, and trees 46 m (150 ft) tall and 183 cm (72 in) in diameter on the most favorable sites in Indiana. In a southern Illinois plantation on a site index of 24.4 m (80 ft), the best tree was 21 cm (8.3 in) in diameter and 12 m (40 ft) tall at age 14, while the average tree was 12 cm (4.8 in) and 7 m (24 ft).

Flowers and nuts

The handbook says flowers begin to appear about mid-April in the South and as late as early June in the north of the range, at about the same time as leafing out. Black walnut is monoecious. Male flowers are slender catkins from axillary buds on the preceding season's outer nodes, and female flowers occur in short terminal spikes on the current shoots. Fertilization follows pollination by 2 to 5 days and is succeeded by development of the husk, the shell and the seed. The handbook says the distinctive tasting nuts are in demand for baked goods and ice cream, and that ground shells are used in many products, including cleaning jet engines and filler in dynamite.

Roots

Silvics describes the mature root system as combining the deep taproot of more xeric trees such as the oaks with the strong laterals of more mesic ones such as maple. It says the system is deep and wide spreading, with a definite taproot at least in early life. A 9-year-old tree excavated from an Indiana plantation had a taproot 2.3 m (7.5 ft) long, with lateral roots extending more than 2.4 m (8 ft) from it.

Wood

The Wood Handbook (FPL-GTR-282, 2021) says the heartwood varies from light to dark brown and the sapwood is nearly white and up to 8 cm (3 in) wide in open-grown trees. The wood is normally straight grained, easily worked and stable in use, heavy, hard, strong and stiff, with good resistance to shock. The handbook says about three-quarters of walnut wood is grown in the Central States, and lists furniture, architectural woodwork, decorative panels, gunstocks and cabinets among the uses.

Wood Handbook figure	Green	At 12% moisture content
Specific gravity (Table 5-3b)	0.51	0.55
Modulus of rupture, lbf per square inch (Table 5-3b)	9,500	14,600
Side hardness, lbf (Table 5-3b)	900	1,010

The green weight of the wood is in the NRS-38 table, the same figure used in the log weight calculator.

Pests and diseases the handbook names

Silvics (1990) says more than 300 insect species were found on black walnut in southern Illinois, of which only a few are considered serious pests, and that black walnut is susceptible to only a few serious diseases.

Defoliators. The walnut caterpillar and the fall webworm.
Borers. An ambrosia beetle, which the handbook says may introduce a Fusarium fungus causing dieback; the flatheaded apple tree borer; the walnut curculio, which damages developing nuts; and the walnut shoot moth, which damages terminal buds and causes forks and crooks. It names the pecan leaf casebearer as a much less damaging relative.
Sucking insects. Aphids, which leave honeydew on leaves, and the walnut lace bug.
Leaf diseases. Walnut anthracnose (Gnomonia leptostyla), target leafspot (Cristulariella pryamidalis, as the handbook spells it) and a leaf spot caused by Mycosphaerella juglandis.
Stem and root. Fusarium cankers and Nectria canker, and two root rots in seedling nurseries from Phytophthora citricola and Cylindrocladium.

The handbook also lists damage from deer, mice, rabbits, squirrels and the yellow-bellied sapsucker, and from late spring frosts. The guide on reporting a pest in the United States gives the office that takes sightings of regulated pests, and pests and diseases by country sets out which ones agencies regulate. Who may apply pesticides is in pesticide licences by country.