Juglans ailantifolia is a very variable plant, but it falls entirely within the described variation of Juglans mandshurica. It may best be considered a regional form of that species[]
This species has often been spelled Juglans ailanthifolia in the literature. However, the original spelling (see
Rev. Hort. (Paris) 50:414, fig. 85-86. 1878) of the name was Juglans ailantifolia[].

Common Name: Japanese Walnut

General Information

Juglans ailanthifolia is a deciduous tree with a dense, wide-spreading crown; it can grow up to 20 metres tall[].
The tree is harvested from the wild for local use as a food, medicine and source of materials. It is grown on a commercial basis for its edible seeds, several varieties having been developed. The tree is also sometimes grown as an ornamental.

Known Hazards

None known

Botanical References

, ,

Range

E. Asia - Russian Far East, Japan.

Habitat

Broad-leaves forests on rich, moist soils[].

Properties

Edibility Rating
Medicinal Rating
Habit	Deciduous Tree
Height	20.00 m
Pollinators	Wind
Self-fertile	Yes
Cultivation Status	Wild

Cultivation Details

This is the hardiest member of the genus, capable of growing in all areas of Britain[]. It is also resistant to the attacks of most insects[]. When dormant, the tree has been known to survive temperatures down to -40°c - the youngest wood was killed, but the tree quickly regenerated the following year[]. New growth, however, is much less hardy and can be damaged by temperatures just above freezing. The tree also requires a hot growing season if it is to fully ripen its wood and be able to tolerate the lower temperatures[].
Requires a deep well-drained loam and a sunny position sheltered from strong winds[, ]. Prefers a slightly alkaline soil[].
This species is cultivated for its edible seed in Japan, it has the potential for producing very superior nuts, especially if hybridized with Juglans cinerea[, ]. Trees can come into bearing within 3 - 4 years from seed[].
Plants produce a deep taproot and they are intolerant of root disturbance[, ]. Seedlings should be planted out into their permanent positions as soon as possible and given some protection since they are somewhat tender when young[, ].
Flower initiation depends upon suitable conditions in the previous summer[]. The flowers and young growths can be destroyed by even short periods down to -2°c, but fortunately plants are usually late coming into leaf[].
Any pruning should only be carried out in late summer to early autumn or when the plant is fully dormant otherwise wounds will bleed profusely and this will severely weaken the tree[].
The plant is said to be resistant to the attacks of most insects[].

Edible Uses

Seed - raw, cooked or used in confectionery[, , , ]. A very good flavour[]. Several fruits are clustered on a long raceme, each fruit is around 50mm long, enclosing a seed around 30mm in diameter[]. The shell is easily cracked[].

An edible oil is obtained from the seed, but it tends to go rancid quickly[].

Young buds (flower?) and fruit stalks - cooked[, , ].

Medicinal

None known

Agroforestry Uses:

Species in this genus can produce chemicals which inhibit the growth of other plants. These chemicals are dissolved out of the leaves when it rains and are washed down to the ground below, reducing the growth of plants under the tree[, , ].
The roots of many members of this genus produce substances that are toxic to many plant species, especially apples (Malus species), members of the Ericaceae, Potentilla spp and the white pines (certain Pinus spp.)[].

Other Uses

A brown dye is obtained from the seed husks and the bark[]. Rich in tannin, it does not require a mordant.

The bark is rich in tannin. It is used as a dye and also medicinally[].

Wood - soft, light, not easily cracked, of good quality. Used for cabinet making etc[, ].

Propagation

The seed is best sown as soon as it is ripe in individual deep pots in a cold frame[]. You need to protect it from mice, birds, squirrels etc. The seed usually germinates in late winter or the spring. Plant out the seedlings into their permanent positions in early summer and give some protection from the cold for their first winter or two.
The seed can also be stored in cool moist conditions (such s the salad compartment of a fridge) over the winter and sown in early spring but it may then require a period of cold stratification before it will germinate[, ].