''Juglans ailantifolia'' (synonyms ''J. cordiformis'' and ''J. sieboldiana'' and '' J. mandshurica'' var. ''sachalinensis''), the Japanese walnut ( ja, 鬼胡桃 ''oni-gurumi''), is a species of walnut native to

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

and Sakhalin. It is a deciduous tree growing to tall, rarely , and 40–80 cm stem diameter, with light grey

bark Bark may refer to: * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, ...

. The

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

are pinnate, 50–90 cm long, with 11-17 leaflets, each leaflet 7–16 cm long and 3–5 cm broad. The whole leaf is downy-pubescent, and a somewhat brighter, yellower green than many other tree leaves. The male flowers are inconspicuous yellow-green

catkin A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind-pollinated (anemophilous) but sometimes insect-pollinated (as in ''Salix''). They contain many, usually unisexual flowers, arranged cl ...

s produced in spring at the same time as the new leaves appear. The female flowers have pink/ red pistils. The fruit is a

nut Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds * Nut (hardware), fastener used with a bolt Nut or Nuts may also refer to: Arts, entertainment, and media Com ...

, produced in bunches of 4-10 together; the nut is spherical, 3–5 cm long and broad, surrounded by a green husk before maturity in mid autumn.

Uses

The edible nuts have an oily texture. The husks are also used to make a yellowish dye. The very bold, decorative leaves and the attractive catkins produced in spring make it an excellent

ornamental tree Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that i ...

for planting in

park A park is an area of natural, semi-natural or planted space set aside for human enjoyment and recreation or for the protection of wildlife or natural habitats. Urban parks are urban green space, green spaces set aside for recreation inside t ...

s and large gardens. File:P4260728.jpg, Heartnut in flower Naturalis Biodiversity Center - L.3711472 - Juglans ailantifolia Carrière var. cordiformis (Makino) Rehder - herbarium sheet.jpg, Herbarium sheet, 19th century Unlike the closely related and very similar

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

n butternut, Japanese walnut is resistant to the

canker A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticultur ...

disease caused by the fungus '' Sirococcus clavigignenti-juglandacearum''. This has led to its being planted as a replacement for butternuts in North America. The two species hybridise readily; the resulting hybrid ''Juglans x bixbyi'' (otherwise known as ''J. cinerea x ailantifolia'' or 'buartnut') is also resistant to canker and is likewise planted as a replacement for butternuts. Japanese walnut is distinguished from butternut by its larger leaves and round (not oval) nuts.
Prospect Rock Permaculture
in Vermont has been backcrossing buartnuts with native butternuts, resulting in 'butterbuarts', which will most likely bear greater resemblance to the butternut parentage, although may also be more susceptible to the canker. The wood is light and takes polish well, but is of much lower quality than Persian walnut wood. It is often used to make

furniture Furniture refers to movable objects intended to support various human activities such as seating (e.g., stools, chairs, and sofas), eating (tables), storing items, eating and/or working with an item, and sleeping (e.g., beds and hammocks). Fu ...

Cultivars

The heartnut is a cultivar of Japanese walnut distinguished by its fruit, which is heart-shaped in cross-section, very hard to crack, and able to yield unbroken nut meat when cracked. The heartnut is a sweet nut without a bitter aftertaste often intrinsic with black and Persian walnuts. This is the subspecies that hybridizes with butternuts, creating 'buartnuts', or ''Juglans x bixbyi''. Toyo Tire evaluated that the shell was very hard and that the fragments were sharp, and it came to be used as a material for snow tires (studless tires).

Diseases

The only significant disease Japanese walnuts are susceptible to is the Walnut Bunch Disease.

External links

* * {{Taxonbar, from=Q1655870 ailantifolia Flora of Japan Flora of Sakhalin Japanese fruit