Juglans regia – Walnut

Explore Juglans regia (Walnut) – its characteristics, habitat, cultivation, propagation, and functional uses and benefits.

Juglans regia | Botanical Characteristics

Common Names: Walnut, English Walnut, Persian Walnut

Family: Juglandaceae

Appearance: A large deciduous tree with a broad crown and pinnate leaves composed of 5–9 ovate leaflets. Produces small greenish flowers in separate male catkins and female clusters, developing into round green husks containing hard-shelled nuts with edible kernels.

Type: Perennial

Evergreen / Deciduous: Deciduous

Layer: Canopy

Root System: Deep taproot with extensive lateral roots; produces juglone, an allelopathic compound inhibiting nearby plant growth

Height: 15–25 m

Width: 12–18 m crown spread

Lifespan: Long-lived, often over 100 years

Growth Rate: Moderate

Fertility: Self-fertile but improved with cross-pollination

Flowers: Monoecious (male and female flowers on the same tree)

Pollinator: Primarily wind-pollinated

Toxicity: Leaves, roots, and husks produce juglone, considered toxic to many plants; husks may irritate skin

Juglans regia | Habitat and Cultivation

Range

• Native Range: Central Asia – from the Balkans through the Himalayas to western China

• Companionship: Although juglone release can limit plant growth, some species such as Cornus, Sambucus show tolerance and may coexist.

• Invasive Range: Not considered invasive

• USDA Hardiness Zone: 5–9

• Minimum Chill Hours Required: 700–1500 depending on cultivar

Resistance/Tolerance

• Poor Soil: Low to moderate tolerance

• Drought: Moderate tolerance once established

• Shade: Low tolerance – requires full sun for nut production

• Flood: Low tolerance – sensitive to waterlogging

• Wind: Moderate tolerance; brittle branches may break in strong winds

• Maritime: Low tolerance – dislikes salty conditions

• Air Pollution: Moderate tolerance

• Fire: Low tolerance

Thriving Conditions

• Sun Exposure: Full sun

• Soil Moisture: Moderate, requires consistent moisture during establishment and nut development

• Soil Type: Deep, fertile, well-drained loam

• Soil pH: Neutral to slightly alkaline (6.5–7.5)

Propagation

• Seeds: Commonly propagated from seed; requires stratification

• Cuttings: Difficult to root; rarely used

• Grafting: Standard method for commercial cultivars, grafted onto seedling rootstocks

Juglans regia | Functional Uses and Benefits

Edible: Nuts widely consumed raw, roasted, or processed; rich in healthy fats, protein, and antioxidants; green husks sometimes used for flavoring

Medicinal: Traditionally used for anti-inflammatory, antimicrobial, and digestive purposes; walnut oil valued for cardiovascular health

Cosmetics: Walnut oil used in skincare and haircare products; ground shells used in natural exfoliants

Animal Feed: Nuts can be used in small amounts; leaves and husks not suitable due to juglone

Fiber: Not used

Timber: High-value hardwood for furniture, cabinetry, and veneer

Firewood: Burns well but often reserved for timber uses

Wind Break: Large trees can act as windbreaks, though juglone limits underplanting

Fence: Not suitable

Cover Crop: No

Mulch: Leaves and husks unsuitable due to juglone

Nitrogen Fixer: No

Dynamic Accumulator: No data

Pollinator Attractor: No – primarily wind-pollinated

Pest Repellent: No

Wildlife Supporter: Nuts provide food for birds, squirrels, and other mammals

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