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Juglandaceae FAMILY Near Threatened

Juglans californica

Juglans californica

Edibility
2/5
Medicinal
1/5

Safety & Hazards

None known

Cultivation Details

HabitDeciduous Tree
GrowthMedium

Juglans californica is native to the more or less Mediterranean climate of southern California, with its hot, dry summers and cooler, moist winters. It is not very hardy in most of the temperate zone, being able to tolerate short periods with temperatures down to between -5 and -10°c when dormant so long as the summer has been hot enough to fully ripen the wood. The young growth in spring is very susceptible to frost damage[1]. Requires a deep well-drained loam and a sunny position sheltered from strong winds[2, 3]. Prefers a slightly alkaline soil[1]. A fairly fast-growing tree in its native habitat, but quite short-lived, dying after about 125 - 150 years[4]. Plants produce a deep taproot and they are intolerant of root disturbance[2, 3]. Seedlings should be planted out into their permanent positions as soon as possible and given some protection since they are somewhat tender when young[2, 3]. Flower initiation depends upon suitable conditions in the previous summer[1]. 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[1]. 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[1]. Plants will generally resprout if top growth is cut back by fire[5]. Closely related to Juglans hindsii[6, 1]

Propagation

The seed is best sown as soon as it is ripe in individual deep pots in a cold frame[7]. 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[8, 7]. Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2026-02-21. <temperate.theferns.info/plant/Juglans+californica>

Pollinators

Wind

References

  1. [1]The New RHS Dictionary of Gardening. 1992. — Huxley. A. · MacMillan Press · 1992 · ISBN 0-333-47494-5 ↩︎Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
  2. [2]RHS Dictionary of Plants plus Supplement. 1956 — F. Chittendon. · Oxford University Press · 1951 · ISBN - ↩︎Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaced in 1992 by a new dictionary (see [ 200 ]).
  3. [3]Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement. — Bean. W. · Murray · 1981 · ISBN - ↩︎A classic with a wealth of information on the plants, but poor on pictures.
  4. [4]The Complete Trees of N. America. Field Guide and Natural History. — Elias. T. · Van Nostrand Reinhold Co. · 1980 · ISBN 0442238622 ↩︎A very good concise guide. Gives habitats, good descriptions, maps showing distribution and a few of the uses. It also includes the many shrubs that occasionally reach tree proportions.
  5. [5]IUCN Red List of Threatened Species — http://www.iucnredlist.org/ ↩︎A list of plants under threat and facing possible extinction, usually with brief details of the threats and information on habitat.
  6. [6]Cornucopia - A Source Book of Edible Plants. — Facciola. S. · Kampong Publications · 1990 · ISBN 0-9628087-0-9 ↩︎Excellent. Contains a very wide range of conventional and unconventional food plants (including tropical) and where they can be obtained (mainly N. American nurseries but also research institutes and a lot of other nurseries from around the world.
  7. [7]Hardy Woody Plants from Seed. — McMillan-Browse. P. · Grower Books · 1985 · ISBN 0-901361-21-6 ↩︎Does not deal with many species but it is very comprehensive on those that it does cover. Not for casual reading.
  8. [8]Propagation of Trees, Shrubs and Conifers. — Sheat. W. G. · MacMillan and Co · 1948 · ISBN - ↩︎A bit dated but a good book on propagation techniques with specific details for a wide range of plants.
  9. [9]Notes on the Temperate Species of Juglans — Grimshaw J.M. · 2003 ↩︎
  10. [10]Flora of N. America — http://flora.huh.harvard.edu/fna/ ↩︎An on-line version of the flora with an excellent description of the plant including a brief mention of plant uses.
  11. [11]A California Flora. — Munz P.A. & Keck D.D. · University of California Press; Los Angeles · 1959 · ISBN - ↩︎An excellent flora but no pictures. Not for the casual reader.
  12. [12]Native American Ethnobotany — Moerman. D. · Timber Press. Oregon. · 1998 · ISBN 0-88192-453-9 ↩︎Very comprehensive but terse guide to the native uses of plants. Excellent bibliography, fully referenced to each plant, giving a pathway to further information. Not for the casual reader.
  13. [PFAF]Plants for a Future — pfaf.org ↩︎