''Juglans ailantifolia'' (synonyms ''J. cordiformis'' and ''J. sieboldiana'' and '' J. mandshurica'' var. ''sachalinensis''), the Japanese walnut (), is a species of

walnut A walnut is the edible seed of any tree of the genus '' Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. They are accessory fruit because the outer covering of the fruit is technically an i ...

native to

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

and Sakhalin.

Description

It is a

deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

growing to tall, rarely , and stem diameter, with light grey bark. The

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

are pinnate, long, with 11–17 leaflets, each leaflet long and 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''). It contains many, usually unisexual flowers, arra ...

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, 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.

Diseases

The only significant disease Japanese walnuts are susceptible to is the walnut bunch disease.

Cultivars

The heartnut is a

cultivar A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...

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''.

Uses

The edible nuts have an oily texture. The husks are also used to make a yellowish dye. The very bold, decorative leaves and catkins produced in spring make it a common ornamental tree for planting in parks and large gardens. File:P4260728.jpg, Heartnut in flower File:Naturalis Biodiversity Center - L.3711472 - Juglans ailantifolia Carrière var. cordiformis (Makino) Rehder - herbarium sheet.jpg, Herbarium sheet, 19th century File:JapaneseWalnutBarkTag.jpg, ''Juglans ailantifolia'' bark at the Cornell Botanic Gardens File:Kus YayoiWalnuts.jpg, Remains of Japanese walnuts from a storage pit of the

Yayoi period The Yayoi period (弥生時代, ''Yayoi jidai'') (c. 300 BC – 300 AD) is one of the major historical periods of the Japanese archipelago. It is generally defined as the era between the beginning of food production in Japan and the emergence o ...

Unlike the closely related and very similar North American butternut, Japanese walnut is resistant to the canker disease caused by the

fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

'' 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. Toyo Tire evaluated the shell of heartnut as being very hard and the fragments sharp, and it came to be used as a material for snow tires (studless tires).

References

External links

* {{Taxonbar, from=Q1655870 ailantifolia Trees of Japan Flora of Sakhalin Japanese fruit Taxa named by Élie-Abel Carrière Plants described in 1878