Texas Walnut, Little walnut, Stewart's little walnut
Juglans microcarpa

Family: Juglandaceae

What it is like

Juglans microcarpa is a deciduous Tree growing to 10 m (32ft) by 10 m (32ft). See above for USDA hardiness. It is hardy to UK zone 6. It is in flower from May to June, and the seeds ripen from October to December. 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 and can tolerate drought.

Height (m): 10

Where it is found

Limestone banks of streams, also in valleys and dry rocky ravines.

South-western N. America - Texas to Mexico.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 2

Seed - raw. The seed is sweet and oily but it is rather small and has a thick shell. The seed is the smallest of this genus. An edible oil is obtained from the seed, it tends to go rancid quickly.

Oil: Oil

Seed: includes nuts, cereals, peas and beans.

Medicine

Rating: 0

Other

Rating:

Sometimes used as a rootstock. 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 - heavy, hard, not strong. It makes a beautiful veneer and has been very over-exploited in the wild for this purpose. It is also used in cabinet making, furniture etc.

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.

Rootstock: Plants used as the rootstock for grafting scions onto.

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

How it is grown

Requires a deep well-drained loam and a sunny position sheltered from strong winds. Prefers a slightly alkaline soil. This species often experiences drought in its native range. 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 for their first winter or two 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. Closely related to J. major, and hybridizes with that species where their ranges overlap.

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: 5-9

Growth:

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

Shade: No shade

Moisture: Moist

Things to keep in mind

Its other names

Local names

Synonyms

J. nana. J. rupestris.