Japanese Walnut
Juglans ailanthifolia

Family: Juglandaceae

What it is like

Juglans ailanthifolia is a deciduous Tree growing to 20 m (65ft) by 15 m (49ft). See above for USDA hardiness. It is hardy to UK zone 4 and is not frost tender. It is in flower in June. The species is monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and is pollinated by Wind. The plant is self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers moist soil.

Height (m): 20

Where it is found

Forests.

E. Asia - Japan.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 3

Seed - raw, cooked or used in confectionery. A very good flavour. 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.

Oil: Oil

Seed: includes nuts, cereals, peas and beans.

Medicine

Rating: 1

The bark is anthelmintic, astringent, diuretic, lithontripic, pectoral, skin, tonic (kidneys).

Anthelmintic: Expels parasites from the gut.

Astringent: Produces contraction in living tissue, reducing the flow of secretions and discharges of blood, mucus, diarrhoea etc.

Diuretic: Acts on the kidneys, promoting the flow of urine.

Kidney: Used in the treatment of kidney diseases

Lithontripic: Removes stones from the kidney, bladder etc.

Pectoral: Relieves respiratory diseases, a remedy for chest diseases.

Skin: Plants used in miscellaneous treatments for the skin.

Tonic: Improves general health. Slower acting than a stimulant, it brings steady improvement.

Other

Rating: 5

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. Plants produce chemicals which can 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.). Wood - soft, light, not easily cracked, of good quality. Used for cabinet making etc. A dynamic accumulator gathering minerals or nutrients from the soil and storing them in a more bioavailable form - used as fertilizer or to improve mulch.

Companion: Companion planting is the careful placement of plants (especially vegetables and herbs) which have been shown to have beneficial effects on one another.

Dye: Plants that provide dyes.

Herbicide: Plants or plant extracts that can inhibit the growth of other plants.

Oil: Vegetable oils have many uses, as lubricants, lighting, soap and paint making, waterproofing etc. This does not include the edible oils unless they are also mentioned as having other uses.

Tannin: An astringent substance obtaied from plants, it is used medicinally, as a dye and mordant, stabilizer in pesticide etc.

Wood: A list of the trees and shrubs that are noted for having useful wood.

Dynamic accumulator: Plants that gather minerals or nutrients from the soil and store them in a more bioavailable form and in high concentration in their tissues. Used as fertilizer or to improve mulch.

Food Forest: Plants for Edible Forest Gardens and Food Forests.

How it is grown

Requires a deep well-drained loam and a sunny position sheltered from strong winds. Prefers a slightly alkaline soil. 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. The young growth in spring, however, can be damaged by late frosts. This species is cultivated for its edible seed in Japan, it has the potential for producing very superior nuts, especially if hybridized with J. 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. Trees have a dense canopy which tends to reduce plant growth below them. We have no specific information for this species, but the roots of several 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.). The leaves of many species also secrete substances that have an inhibitory affect on plants growing underneath them. All in all this is not a very good companion plant. The plant is heat tolerant in zones 8 through 5. (Plant Hardiness Zones show how well plants withstand cold winter temperatures. Plant Heat Zones show when plants would start suffering from the heat. The Plant Heat Zone map is based on the number of "heat days" experienced in a given area where the temperature climbs to over 86 degrees F (30°C). At this temperature, many plants begin to suffer physiological damage. Heat Zones range from 1 (no heat days) to 12 (210 or more heat days). For example Heat Zone. 11-1 indicates that the plant is heat tolerant in zones 11 through 1.) For polyculture design as well as the above-ground architecture (form - tree, shrub etc. and size shown above) information on the habit and root pattern is also useful and given here if available. The plant growth habit is a standard with a non-suckering single trunk. In garden design, as well as the above-ground architecture of a plant, root structure considerations help in choosing plants that work together for their optimal soil requirements including nutrients and water. The root pattern is branching: a heart root, dividing from the crown into several primary roots going down and out .

Propagating it: 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.

Best place to grow: Woodland Garden Canopy;

Habit: Tree

Hardiness: 4-8

Growth:

Soil: Light (sandy), medium, heavy (clay)

Shade: No shade

Moisture: Moist

Things to keep in mind

Its other names

Local names

Heartnut

Synonyms

J. allardiana. J. correctata. J. lavellei. J. mirabunda. J. sachalinense. J. sieboldiana. non Goeppe