Black Walnut

Ecology & Conservation

Proximity Score

1

Native Status

❌ Outaouais ❌ Ottawa ❌ QC ✅ ON

Closest Direction

S

CEC Eco-Regions

8 – Eastern Temperate Forests, 8.1 – Mixed Wood Plains, 8.1.1 – Eastern Great Lakes and Hudson Lowlands

Rarity Notes

Globally secure (G5, IUCN Least Concern). In Ontario ranked S4, reflecting adequate populations in the Carolinian zone and southern Great Lakes region. Not listed under SARA or COSEWIC. In Quebec ranked SNA as it is considered introduced. Ottawa populations are rare and introduced, though native elsewhere in Ontario.

S22 G5, IUCN LC, S4 ON, SNA QC; S26 not SARA listed; S62 Rare introduced in Ottawa

Rarity Ranks

QC SNA – Not Applicable, ON S4 – Apparently Secure

Migration

Stable

Ecological Context

Black walnut is a scattered component of mixed mesophytic forests on deep, well-drained alluvial soils and lower slopes. It is most abundant in coves and bottomlands in the central hardwood region, associating with sugar maple, white ash, yellow-poplar, and oaks. Native to Ontario but introduced in Quebec, it reaches the northern edge of its natural range in southern Ontario.

S41 mixed mesophytic forests; S1 native ON, introduced QC; S10 rich bottomland habitat

Permaculture & Companion Planting

Roles

Erosion Control, Fire Retardant, Fortress/Barrier, Insectary Plant, Nutrient Accumulator, Shelterbelter, Wildlife Habitat

S73/S29/S72 Evidence: Erosion Control: S72 Hemenway (tables: 6-2, 10-1, appendix_a, pp. 96, 149, 186)] | Fire Retardant: S73 [MEDIUM]: S11 Fire Tolerance = High (not definitional)] | Fortress/Barrier: S61 keyword match: thorns? (supporting signal only)] | Insectary Plant: S72 Hemenway (tables: 6-2, 10-1, appendix_a, pp. 96, 149, 186)] | Nutrient Accumulator: S72 Hemenway (tables: 6-2, 10-1, appendix_a, pp. 96, 149, 186)] | Shelterbelter: S72 Hemenway (tables: 6-2, 10-1, appendix_a, pp. 96, 149, 186); S72 Hemenway (tables: 6-2, 10-1, appendix_a, pp. 96, 149, 186)] | Wildlife Habitat: S72 Hemenway (tables: 6-2, 10-1, appendix_a, pp. 96, 149, 186)]

Notes

The strong allelopathic effect of juglone, exuded from roots, leaves, bark, and nut husks, makes black walnut a challenging companion plant. Design guilds must be restricted to juglone-tolerant species. In food forest settings it functions better as a standalone canopy element or interplanted with nitrogen-fixers like Elaeagnus spp. that boost growth and tolerate juglone.

S41 juglone mechanism; S29 design context; S72 allelopathic note in appendix

Medicinal Properties

ℹ

Always consult a qualified healthcare provider before using any plant for medicinal purposes. The information provided is compiled from secondary sources for educational purposes only.

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Category

Alterative, Anodyne, Astringent, Vermifuge, Laxative, Dermatological Aid, Anthelmintic

S29 alterative, anodyne, astringent, vermifuge, laxative; S28 dermatological aid, anthelmintic, gastrointestinal aid

Notes

Cherokee, Delaware, and Comanche peoples used black walnut extensively. Bark infusion treated diarrhea and skin diseases; bark was chewed for toothache. Fruit husk juice was applied for ringworm, and pulverized leaves treated the same. Delaware used a strong bark decoction as a cathartic and emetic. Health Canada lists Juglans nigra as an approved herbal name.

S28 35 drug/medicine uses; S29 detailed medicinal uses; S36 Health Canada approved

Edibility & Foraging

ℹ

Never ingest a plant unless you have 100% certainty of its identity and have consulted multiple reputable sources. The information provided in the Localeaf Plant Database is compiled from secondary sources for educational and historical purposes only.

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✅ Edible    ✅ Commonly Eaten

Foraging Notes

Nuts are sweet and rich with a distinctive flavor, widely used in baking, confections, and ice cream. Cherokee, Comanche, and Dakota peoples used the nuts as food, dried them for storage, and made soup. An edible oil is pressed from the seed but goes rancid quickly. The sap can be tapped in spring and boiled into syrup or sugar. Unripe fruits can be pickled.

S28 18 food uses; S29 edible seed, oil, sap; S41 nuts ripen Sep-Oct

Toxicity

☠️ High Toxicity

Juglone (5-hydroxy-1,4-naphthoquinone), concentrated in roots, leaves, bark, and nut husks, is the primary toxic compound. At high concentrations it is lethal to some plants; at trace levels it may actually promote seedling growth. Contact dermatitis has been reported in humans handling husks. The USDA rates toxicity as slight. Cherokee sources note bark should be used cautiously in medicine because it is poisonous.

S11 Toxicity=Slight; S29 contact dermatitis; S41 juglone mechanism; S28 Cherokee poison warning; S31 juglone in phytochemical database

Seed Source

• Aylmer collected
• OWSL