Common Name: Desert Scrub Oak

General Information

Quercus turbinella is an evergreen or semi-evergreen shrub or a small tree that usually grows 1 - 2 metres tall, but can sometimes reach 5 metres, with reports of plants 10 - 20 metres tall. Spreading at the roots, it can form thickets[, , ].
The plant is harvested from the wild for local use as a source of materials and perhaps also as a food and a medicine. It is used in soil stabilization projects.
Quercus turbinella has a large range and currently no known 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

Range

Southwest N. America - Nevada, Utah, Colorado, southeast California, Arizona New Mexico, western Texas, northern Mexico

Habitat

Semiarid, lower elevation areas of chaparral, shrub deserts, oak woodlands and oak-pine forests, growing with pines, junipers and manzanitas, and becoming the dominant shrub in Arizona chaparral; at elevations from 500 - 1,500 metres[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	2.00 m
Pollinators	Wind
Cultivation Status	Wild

Cultivation Details

Quercus turbinella is a very cold-hardy tree, tolerating temperatures down to around -25°c when dormant[]. Native to semi-arid environments, characterized by a biseasonal precipitation pattern with summer and winter precipitation and spring and autumn droughts, the mean annual precipitation can range from 410 - 640mm[]. Suitable for growing in cold, dry areas, it also seems to be able to cope with moister climates such as western England[, though it needs hot summers if it is to thrive1212].
The plant grows well on dry hillsides and mesas and tolerates a wide range of soil types, growing best on sandy to clay loams[]. The soils are often slightly acidic. It is not restricted to deep soils and can grow on shallow, broken and fractured substrates. Soils are typically coarse-textured and poorly developed[]. Established plants are drought tolerant[].
Plants can resprout freely from the base if top-killed by fire[].
This species hybridises freely with the most disparate-seeming partners, including the European oak (Quercus robur), and is a parent of several wild hybrids[].

Edible Uses

Indigenous peoples use the acorns for food[, ]. The brown, ovoid seed is up to 20mm long and 11mm 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 is rated as having 'high potential' for erosion control and for long-term revegetation projects, but it is of little value in short-term revegetation[].

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[, ].

Indigenous peoples use the wood for fashioning tools[].
The wood of many Oak species is a favoured fuel - burning well and giving off a lot of heat[].

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.