Common Name: Live Oak

General Information

Quercus chrysolepis is an evergreen shrub or a tree that in some habitats is less than 5 metres tall but in favoured sites can grow up to 30 metres tall with a dense, wide-spreading crown. The bole of larger specimens can be more than 300cm in diameter and, in closed stands, can be free of branches for up to 12 metres[, ].
The tree yields an excellent quality timber and has been widely exploited for this in the past. At present available supplies are limited and so the tree is not used commercially. The tree is also harvested from the wild for local use as a food and source of materials, and is often grown as an ornamental[].
This species has an extensive range, large population and few threats. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

All parts of the plant contain tannins. Whilst tannins are found in many foods, and have a range of medicinal uses. They are usually only present in low concentrations. In some foods made from oaks (particularly the seeds), the tannin content can be quite high unless the food is treated to reduce tannin content.
Tannins are only of low toxicity and, because of their bitter taste and astringency, are unlikely to be eaten in large quantities. However, if they are taken in excess, they can cause stomach pains; constipation followed by bloody diarrhoea: excessive thirst; and excessive urination[].

Botanical References

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Range

South-western N. America - western Oregon, California, Nevada, Arizona, New Mexico, northern Mexico.

Habitat

Found in a variety of habitats, often as the dominant species, it is a tall tree in deep, cool, narrow canyons and is a low thicket-forming shrub on high windswept slopes; at elevations from 200 - 2,700 metres[, , , ].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	20.00 m
Growth Rate	Slow
Pollinators	Wind
Cultivation Status	Ornamental, Wild

Cultivation Details

Quercus chrysolepis is a moderately cold-hardy tree, tolerating temperatures down to around -15°c when dormant. It grows best in areas with hot summers. In areas with cooler summers, such as the maritime regions of the temperate zone, it often grows poorly, failing to properly ripen its wood and suffering frost damage over the winter[, ].
Prefers a good deep fertile loam which can be on the stiff side[, ]. Young plants tolerate reasonable levels of side shade[]. Tolerates moderate exposure, surviving well but being somewhat stunted[].
A slow-growing but long-lived tree in the wild[]. It can take more than 20 years before it begins to produce seed[].
The tree flowers on new growth produced in the spring, the seed ripening in its first year[, ].
Seed production is cyclic, occasional years of high yields being followed by several years of low yields[].
Seedlings soon develop a taproot and become intolerant of root disturbance, they should be planted into their permanent positions whilst young[].
When killed by forest fires the tree often resprouts from the roots[].
The tree's growth form and other characteristics can vary greatly, which allows it to live in a variety of natural settings. Within the North Coast Ranges of California, with plentiful rainfall and mild temperatures, it can grow more than 20 metres tall and lives among massive Douglas Fir and Madrone in an evergreen forest of conifers and hardwoods. In southern California, dense forests of medium-sized trees blanket slopes above 1,300 metres. Possibly the most typical growth form is seen in dry canyons, along cracked rock walls. Here, this species grows in a more spreading pattern rather than upwards and usually reaches less than 15 metres tallt. Finally, under extremely open and arid conditions, with virtually no soil development, it becomes a low spreading shrub as pure stands or within a chaparral mosaic present on slopes[].
Hybridizes freely with other members of the genus[].
Plants in this genus are notably resistant to honey fungus[].

Edible Uses

Seed - cooked[, ]. A staple food for several native North American Indian tribes[]. The seed is usually about 15 - 30mm long and 10 - 20mm wide[, , ] and can be up to 5cm long and wide[].
The seed is usually cooked before eating, though it can also be eaten raw. It can be eaten whole, though it is more commonly dried, then ground into a powder and used as a thickening in stews etc or mixed with cereals for making bread.
In some species, especially many of those classified as 'white oaks', the seeds are low in tannins and have a more or less sweet and agreeable flavour. The seed of most species, however, have a very bitter flavour, due especially to the presence of tannins. In these species there are various processes that can remove or at least reduce the amount of these bitter substances (although other water-soluble substances, including some minerals, will also be removed).
Tannins are water-soluble and therefore the easiest way to remove or reduce tannin levels is by soaking in water. A few different methods are listed:-
A traditional method of preparing the seed was to bury it in boggy ground overwinter and allow the wet soil to gradually leach the tannins. The germinating seed was dug up in the spring when it would have lost most of its astringency and bitterness.
Another method was to wrap the seeds in a cloth bag and place them in a stream for several weeks.
Drying the seed and grinding it to a powder before soaking speeds up the process. The fastest method is to use hot water, by cooking the powder and changing the water several times until the cooking water is no longer bitter. Alternatively, you can use cold water (which is reported to produce the best quality flour). In this case, you soak the powdered seed in cold water for 12 - 24 hours then discard the water. Repeat this process for a number of times until the soak water is no longer bitter.

The roasted seed of many Quercus species has been used as a coffee substitute.

Medicinal

Quercus (oak) species are used in the traditional medicine of many cultures, being valued especially for their tannins. Various parts of the plant can be used, most frequently it is the leaves, bark, seeds, seed cups or the galls that are produced as a result of insect damage. A decoction or infusion is astringent, antibacterial, antifungal, antiseptic, styptic and haemostatic. It is taken internally to treat conditions such as acute diarrhea, dysentery and haemorrhages. Externally, it is used as a mouthwash to treat toothache or gum problems and is applied topically as a wash on cuts, burns, various skin problems, haemorrhoids and oral, genital and anal mucosa inflammation[]. Extracts of the plant can be added to ointments and used for the healing of cuts[, ].

Agroforestry Uses:

The plant's deep root system and its ability to grow on rocky, unstable sites make it useful for soil stabilization on steep slopes[].

Other Uses

The leaves of most species in this genus are more or less rich in tannins. A mulch of the partially decayed leaves can be placed around vulnerable plants in order to repel slugs, snails, grubs etc, and these will in time break down to add humus and nutrients to the soil. Fresh leaves should be used with caution, however, since as these decay they utilize some of the nitrogen in the soil and thus can inhibit plant growth[, ]..

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 and is also used by many cultures to make ink[, ].
The bark of oak trees is also usually rich in tannins and can be used as a dyestuff and for waterproofing rope[, ].

The acorn cups, soaked in water containing iron, produce a black dye[].

The wood is heavy, hard, tough, very strong, close grained, compact, shock resistant[, , ]. This tree produces the best western oak timber, but its commercial value is limited by the small quantities available. It has a variety of uses including making agricultural implements, tool handles, ship frames, wheels and wagons[, , ].
The wood is an excellent fuel[]. An important source of firewood in southern California[].

Propagation

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[]. Trees should not be left in a nursery bed for more than 2 growing seasons without being moved or they will transplant very badly.