Japanese Walnut

Scientific name: Juglans ailantifolia

Overview

Japanese Walnut, known locally as Onigurumi, is a deciduous walnut from Japan and nearby island populations. Its brown timber is used in furniture and other decorative work. The name Juglans ailantifolia remains familiar in horticulture and timber references, while Kew currently places it under Juglans mandshurica var. sachalinensis. This page retains the familiar name while documenting that botanical relationship.

Quick Facts

  • Common Name: Japanese Walnut
  • Scientific Name: Juglans ailantifolia
  • Kew Accepted Name: Juglans mandshurica var. sachalinensis
  • Family: Juglandaceae
  • Region: Asian Woods
  • Other Names: Onigurumi, Japanese White Walnut
  • Native Range: Japan and the Kuril Islands under Kew’s accepted variety
  • Tree Size: Commonly around 20 m (66 ft); larger trees occur
  • Average Dried Weight: Approximately 530 kg/m³ (33 lb/ft³), based on a reported mean air-dry specific gravity of 0.53; individual material varies
  • Janka Hardness: A reliable taxon-specific value was not verified
  • Color: Dull brown heartwood with greyish-white sapwood
  • Grain: Variable; inspect individual boards
  • Texture: Coarse, with relatively large vessels

Identification Characteristics

Japanese timber descriptions distinguish brown heartwood from pale sapwood and note relatively inconspicuous growth rings. Research on Japanese material also found substantial variation in heartwood color associated with growing conditions. A color match therefore supports comparison but does not prove identity. Samples need a supplier record or documented tree provenance.

Key identification traits include:

  • Brown heartwood contrasting with greyish-white sapwood
  • Visible vessel openings and coarse texture
  • Growth rings may be less obvious than in ring-porous hardwoods
  • Japanese provenance or a reliable botanical identification
  • Older labels may use Juglans sieboldiana

Working Properties

Japanese references describe moderate weight and hardness, relatively little distortion, and easy cutting with a good surface finish. Those qualities support interior woodworking. Normal precautions still apply: condition stock before joining, follow the grain during planing, and test finishes on an offcut.

  • Machining: Generally easy to cut and shape
  • Surface Preparation: Sharp tools help achieve a clean finish
  • Conditioning: Acclimate stock to the intended indoor environment
  • Joinery: Test adhesive performance on prepared offcuts
  • Finishing: Compare oil and film finishes on a sample before use

Safety Note

Use effective dust extraction and appropriate eye and respiratory protection when cutting or sanding. Avoid unnecessary dust exposure and keep fine sanding dust out of the work area. Traditional use of walnut timber does not establish that its dust is harmless.

Common Uses

Documented uses in Japanese timber references include:

  • Furniture
  • Flooring
  • Architectural woodwork
  • Carving
  • Implements and specialty wooden parts

Sustainability & Notes

Japanese references describe limited standing resources and some planting of this walnut. Obtain harvest-origin and supplier documentation rather than assuming that all material is plantation-grown. The accepted name and the familiar name may differ on paperwork; record both. A verified conservation assessment for this exact variety is not supplied here.

Comparative Notes & Related Species

Related Guides

Compare Wood Properties

See how this species ranks in density and hardness using our Wood Density & Janka Hardness Chart. You can also explore Hardest Woods, Softest Woods, and Most Dense Woods for quick comparisons.

Collector Notes

Keep the original label Juglans ailantifolia in the collection history and add Juglans mandshurica var. sachalinensis as the current Kew treatment. Record location and drying history, especially when comparing heartwood color. A natural sapwood-to-heartwood transition is useful in a reference specimen; preserve a prepared end-grain face alongside the finished display surface.

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Resources

Authoritative botanical and forestry references used in compiling information about this species include:

• USDA Forest Service – Wood Handbook: Wood as an Engineering Material
https://www.fpl.fs.usda.gov/products/publications/

• The Wood Database – Global reference for wood identification, physical properties, and woodworking characteristics
https://www.wood-database.com/

• Royal Botanic Gardens, Kew – Plants of the World Online – Botanical taxonomy and species distribution database
https://powo.science.kew.org/

• International Union for Conservation of Nature (IUCN Red List) – Global conservation status assessments
https://www.iucnredlist.org/

• Convention on International Trade in Endangered Species (CITES) – International trade regulations for protected plant species
https://cites.org/

Additional forestry publications, academic research papers, and regional timber studies may also be referenced where available.

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Availability & Where to Buy

Exotic hardwood availability can vary significantly depending on region, sustainability regulations, and supplier inventory.

As this archive grows, recommended suppliers and specialty wood retailers will be listed here to help woodworkers locate responsibly sourced material.

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