Common Name: Arizona Walnut

General Information

Juglans major is a deciduous tree with stout, spreading branches forming an open, rounded crown; it can grow from 5 - 18 metres tall. The straight bole can be 130cm in diameter[].
The plant is harvested from the wild for local use as a food and source of materials.
Juglans major has a large native range and its population is assumed to be large since in the US it can be dominant in some habitats and can form pure stands. Information for Mexico is not widely available but the species was reported as threatened from the country in 2010. In the US, the species is considered stable and is rarely used for timber. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2018)[].

Known Hazards

None known

Botanical References

, ,

Range

Southwestern N. America - Arizona, New Mexico, Oklahoma, Texas, northern Mexico

Habitat

Semi-arid areas, growing in broadleaved woodland, oak and conifer woodland, usually in moister places such as near rivers or by ephemeral streams, sometimes forming pure stands[]. Dry rocky ravines and stream beds, 700 - 2,300 metres[].

Properties

Conservation Status	Least Concern
Edibility Rating
Other Uses Rating
Habit	Deciduous Tree
Height	15.00 m
Growth Rate	Fast
Pollinators	Wind
Self-fertile	Yes
Cultivation Status	Wild

Cultivation Details

Juglans major is native to semi-arid areas of northern Mexico and southern USA, where it can be found at elevations up to 2,300 metres. It is said to have a hardiness rating of 8 - 9 (tolerating short periods with temperatures falling to around -4°c to -8°c), though it is likely to be hardier. There are examples of mature plants up to 18 metres tall in northern England (hardiness zone 6), for example[].
Requires a deep well-drained loam and a sunny position sheltered from strong winds[, ]. Prefers a slightly alkaline soil[]. Plants are fast-growing when young[].
Plants are fairly long-lived (to about 400 years) and produce a deep taproot, they are intolerant of root disturbance[, , ]. Seedlings should be planted out into their permanent positions as soon as possible and given some protection for their first winter or two since they are somewhat tender when young[, ].
Trees produce good crops of seeds every 2 - 3 years in the wild[]. Natural regeneration is very low because most seeds are consumed by wildlife[].
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[].
This species is closely related to and sometimes considered to be no more than a sub-species of Juglans microcarpa[, ]. It hybridizes with that species where their ranges overlap[], but has been shown to be genetically quite distinct[].

Edible Uses

Seed - raw or cooked[]. The seed is rather small, but it is sometimes eaten[, , ]. Of little value[]. The seed is large and sweet[] with a thick shell[, ]. There are about 45 seeds to the pound[]. The fruits are produced in groups of 1 - 3, around 25 - 35mm in diameter containing a single, thick-shelled nut 18 - 27mm in diameter[].

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

Medicinal

None known

Agroforestry Uses:

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.)[].
All in all species in this genus do not tend to make good companion plants[].

Other Uses

A golden brown dye can be obtained from the seed husks[].
A light brown dye is obtained from the young twigs[].

This species is sometimes used as a rootstock[].

A very attractive wood rivalling that of Juglans nigra, the black walnut, in quality[]. However, the limited range and smaller size of the tree have restricted its commercial use[].

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[, , ]. Germination rates are usually less than 50%[].