Arizona Walnut (Juglans major)

J. microcarpa major. J. rupestris major. J. torreyi.
Common Name Latin Name Plant Family
Arizona Walnut
Juglans major

This species is sometimes used as a rootstock[183].

A golden brown dye can be obtained from the seed husks[257].

A light brown dye is obtained from the young twigs[257].

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[18, 20, 159]. 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.)[200].

Wood – this very attractive wood rivals that of J. nigra, the black walnut, in quality[229]. However, the limited range and smaller size of the tree have restricted its use[229].

  • Medicinal Use

    None known

  • Edible Use

    Seed – raw or cooked[257]. The seed is rather small, but it is sometimes eaten[82, 161, 183]. Of little value[177]. The seed is large and sweet[227] with a thick shell[200, 227]. There are about 45 seeds to the pound[227]. The seeds are 25 – 40mm in diameter[229].

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

  • Cautionary Notes

    None known

Cultivation & Habitat

The seed is best sown as soon as it is ripe in individual deep pots in a cold frame[80]. 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[78, 80, 113]. Germination rates are usually less than 50%[227].
Requires a deep well-drained loam and a sunny position sheltered from strong winds[1, 11]. Prefers a slightly alkaline soil[200]. Plants are fast-growing when young[227]. This species is closely related to and sometimes considered to be no more than a sub-species of J. microcarpa[11, 229]. It hybridizes with that species where their ranges overlap[229]. If it is a distinct species then perhaps its correct name should be J. torreyi[11]. Trees produce good crops of seeds every 2 – 3 years in the wild[227]. Natural regeneration is very low because most seeds are consumed by wildlife[229]. Plants are fairly long-lived (to about 400 years) and produce a deep taproot, they are intolerant of root disturbance[1, 11, 229]. 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[1, 11]. Flower initiation depends upon suitable conditions in the previous summer[200]. 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[200]. 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[200]. 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.)[200]. 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[K].
Southern N. America – New Mexico to Arizona.

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*None of the information on this website qualifies as professional medical advice. Take only what resonates with your heart and use your own personal responsibility for what’s best for you. For more information [brackets] [000], see bibliography.