Practical
Plants

Juglans californica

California Walnut

a perennial woody deciduous member of the Juglans genus in the family Juglandaceae.

No photo available

Taxonomy and growth

Genus
Juglans
Life cycle
perennial
Foliage
deciduous
Woodiness
woody
Growth rate
moderate
Fertility
Self fertile, Wind
Flower type
monoecious
Pollinators
Wind

Uses

Edible uses

This section contains historical Plants For A Future notes marked noncommercial.

Seed - raw, cooked or used in pies, confections etc[5]. A sweet flavour[8]. The seed is small with a thick shell but it makes good eating[5]. The seed is up to 15mm in diameter[8]. An edible oil is obtained from the seed, it tends to go rancid quickly.

Product or use
Oil
Plant part
Seed

Medicinal uses

Historical medicinal uses. These records describe reported uses. They do not establish safety or effectiveness. Ask a qualified health professional before using any plant medicinally.

This section contains historical Plants For A Future notes marked noncommercial.

An infusion of the leaves is used to treat thin blood[9].

Product or use
Blood tonic

Material uses

This section contains historical Plants For A Future notes marked noncommercial.

Often used as a rootstock for J. regia. 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[4][6][3]. 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.)[7]. Wood - moderately coarse-grained. An attractive wood, but the frequent branching pattern of the trunk limits the use of this wood commercially[8]

Product or use
Herbicide
Product or use
Wood

Ecology and functions

Ecosystem niche
Canopy

Rootstock

Environment

Range
South-western N. America - California.
Habitat
Moist or dry gravelly soils along river courses and bottomlands[8]. Locally common in oak woods below 750 metres[10].
Light
full sun
Shade tolerance
no shade
Water
moderate
Hardiness
Zone 8+
Soil textures
sandy, loamy, clay
Soil pH
acid, neutral, alkaline
Drainage
well drained
Tolerates Nutritionally Poor Soil
No
Drought
intolerant

Propagation

This section contains historical Plants For A Future notes marked noncommercial.

The seed is best sown as soon as it is ripe in individual deep pots in a cold frame[12]. 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[11][12].

Cultivation

This section contains historical Plants For A Future notes marked noncommercial.

Requires a deep well-drained loam and a sunny position sheltered from strong winds[1][2]. Prefers a slightly alkaline soil[7]. Plants are not very hardy in Britain, tolerating temperatures down to between -5 and -10°c[7]. A fairly fast-growing tree in its native habitat, but quite short-lived, dying after about 125 - 150 years[8]. Plants produce a deep taproot and they are intolerant of root disturbance[1][2]. Seedlings should be planted out into their permanent positions as soon as possible and given some protection since they are somewhat tender when young[1][2]. Flower initiation depends upon suitable conditions in the previous summer[7]. 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[7]. 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[7]. 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.)[7]. 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]. Closely related to J. hindsii[5][7]

References

  1. F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press 1951-00-00

    ↩1↩2↩3

  2. Bean. W. Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement. Murray 1981-00-00

    ↩1↩2↩3

  3. McPherson. A. and S. Wild Food Plants of Indiana. Indiana University Press 1977-00-00 ISBN 0-253-28925-4

    ↩

  4. Philbrick H. and Gregg R. B. Companion Plants. Watkins 1979-00-00

    ↩

  5. Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications 1990-00-00 ISBN 0-9628087-0-9

    ↩1↩2↩3

  6. Riotte. L. Companion Planting for Successful Gardening. Garden Way, Vermont, USA. 1978-00-00 ISBN 0-88266-064-0

    ↩

  7. Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press 1992-00-00 ISBN 0-333-47494-5

    ↩1↩2↩3↩4↩5↩6↩7↩8

  8. Elias. T. The Complete Trees of N. America. Field Guide and Natural History. Van Nostrand Reinhold Co. 1980-00-00 ISBN 0442238622

    ↩1↩2↩3↩4↩5

  9. Moerman. D. Native American Ethnobotany Timber Press. Oregon. 1998-00-00 ISBN 0-88192-453-9

    ↩

  10. Munz. A California Flora. University of California Press 1959-00-00

    ↩

  11. Sheat. W. G. Propagation of Trees, Shrubs and Conifers. MacMillan and Co 1948-00-00

    ↩

  12. McMillan-Browse. P. Hardy Woody Plants from Seed. Grower Books 1985-00-00 ISBN 0-901361-21-6

    ↩1↩2

Edit this page