Practical
Plants

Quercus douglasii

Blue Oak

a perennial woody deciduous member of the Quercus genus in the family Fagaceae.

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Taxonomy and growth

Family
Fagaceae
Genus
Quercus
Life cycle
perennial
Foliage
deciduous
Woodiness
woody
Growth rate
slow
Height
12 m
Fertility
Wind
Flower type
monoecious
Pollinators
Wind

Uses

Edible uses

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

Seed - cooked[8]. The seed has been used as a staple food by some native North American Indian tribes[8]. Somewhat sweet[11][9][2][4]. A good size, to 25mm long and wide[12][6]. It can be dried, ground into a powder and used as a thickening in stews etc or mixed with cereals for making bread. The seed from some trees contains bitter tannins, these can be leached out by thoroughly washing the seed in running water though many minerals will also be lost. Either the whole seed can be used or the seed can be dried and ground it into a powder. It can take several days or even weeks to properly leach whole seeds, one method was to wrap them in a cloth bag and place them in a stream. Leaching the powder is quicker. A simple taste test can tell when the tannin has been leached. The traditional method of preparing the seed was to bury it in boggy ground overwinter. The germinating seed was dug up in the spring when it would have lost most of its astringency. The roasted seed is a coffee substitute.

Product or use
Coffee
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.

Any galls produced on the tree are strongly astringent and can be used in the treatment of haemorrhages, chronic diarrhoea, dysentery etc[9]. A poultice of the ground galls and salt has been used in the treatment of burns, sores and cuts[8]. It has also been used as a wash for sore eyes[8]. The leaves have been chewed as a treatment for sore throats[8].

Product or use
Astringent
Product or use
Poultice
Product or use
Skin

Material uses

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

A mulch of the leaves repels slugs, grubs etc, though fresh leaves should not be used as these can inhibit plant growth[5]. Oak galls are excrescences that are sometimes produced in great numbers on the tree and are caused by the activity of the larvae of different insects. The insects live inside these galls, obtaining their nutrient therein. When the insect pupates and leaves, the gall can be used as a rich source of tannin, that can also be used as a dyestuff[9]. The branches have been used to make rims for twined work baskets[8]. The acorn meal has been used to mend cracks in clay pots[8]. The seed cups are used as buttons[10]. Wood - hard, heavy, strong, brittle. It has a strong cross-grain and is difficult to split[7]. Of little commercial value, it is used mainly for fuel[12][7].

Product or use
Adhesive
Product or use
Basketry
Product or use
Buttons
Product or use
Fuel
Product or use
Repellent
Product or use
Tannin
Product or use
Wood

Ecology and functions

Ecosystem niche
Canopy

Environment

Range
South-western N. America - California.
Habitat
Dry soils in valleys, rolling hills and lower mountain slopes to 1350 metres[11][12], often forming extensive stands[7].
Light
full sun
Shade tolerance
light shade
Water
moderate
Hardiness
Zone 7+
Soil textures
loamy, clay
Soil pH
acid, neutral, alkaline
Tolerances
high wind
Wind
Yes
Tolerates Nutritionally Poor Soil
No
Drought
intolerant

Propagation

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

Seed - it quickly loses viability if it is allowed to dry out. It can be stored moist and cool overwinter but is best sown as soon as it is ripe in an outdoor seed bed, though it must be protected from mice, squirrels etc. Small quantities of seed can be sown in deep pots in a cold frame. Plants produce a deep taproot and need to be planted out into their permanent positions as soon as possible, in fact seed sown in situ will produce the best trees[3]. Trees should not be left in a nursery bed for more than 2 growing seasons without being moved or they will transplant very badly.

Cultivation

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

Prefers a good deep fertile loam which can be on the stiff side[1][3]. Young plants tolerate reasonable levels of side shade[6]. Tolerates moderate exposure, surviving well but being somewhat stunted[6]. Prefers warmer summers than are usually experienced in Britain, trees often grow poorly in this country and fail to properly ripen their wood resulting in frost damage overwinter[6]. A slow-growing but long-lived tree. Seed production is cyclic, a year of high yields being followed by 2 - 4 years of low production[7]. The tree flowers on new growth produced in spring, the seed ripening in its first year[6][7]. This species is notably resistant to honey fungus[13][6]. Hybridizes freely with other members of the genus[6]. Intolerant of root disturbance, trees should be planted in their permanent positions whilst young[3].

References

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

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  2. Tanaka. T. Tanaka's Cyclopaedia of Edible Plants of the World. Keigaku Publishing 1976-00-00

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

    ↩1↩2↩3

  4. Yanovsky. E. Food Plants of the N. American Indians. Publication no. 237. U.S. Depf of Agriculture.

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

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  6. 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

  7. 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

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

    ↩1↩2↩3↩4↩5↩6↩7

  9. Grieve. A Modern Herbal. Penguin 1984-00-00 ISBN 0-14-046-440-9

    ↩1↩2↩3

  10. Mabey. R. Food for Free. Collins 1974-00-00 ISBN 0-00-219060-5

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  11. Elias. T. and Dykeman. P. A Field Guide to N. American Edible Wild Plants. Van Nostrand Reinhold 1982-00-00 ISBN 0442222009

    ↩1↩2

  12. Sargent. C. S. Manual of the Trees of N. America. Dover Publications Inc. New York. 1965-00-00 ISBN 0-486-20278-X

    ↩1↩2↩3

  13. RHS. The Garden. Volume 112. Royal Horticultural Society 1987-00-00

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