Common Name: Black Oak

General Information

Quercus emoryi is usually an evergreen shrub when growing in poor, shallow or dry soils, developing into a tree with a spreading, rounded crown in richer, deeper and moister soils; it can grow up to 20 metres tall. The bole can be up to 75cm in diameter[, ].
The tree is harvested from the wild for local use as a food, medicine and source of materials. The sweet-tasting seeds are harvested on a large scale and sold in markets, whilst the wood is a very important fuel crop and so the trees are often managed for the production of firewood.
Quercus emoryi has a large range and is widespread, occurring as the codominant species in many of its habitats. Its range, population density and threats are largely unknown in Mexico, but the species is generally secure. There are many threats facing Emory Oak currently, but in the majority of cases intensity is unknown and the effects will likely be seen over a long period of time. 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

South-western N. America - Arizona, New Mexico, Texas and northern Mexico.

Habitat

Canyons, dry foothills and mountain slopes, 1350 - 2350 metres[], growing best in sheltered valleys[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	12.00 m
Growth Rate	Slow
Pollinators	Wind
Cultivation Status	Semi-cultivated, Wild

Cultivation Details

Quercus emoryi is a moderately cold-hardy tree, tolerating temperatures down to around -15°c when dormant. It grows in arid to semiarid climates with low amounts of biseasonal rainfall. The climate has mild, wet winters and hot, wet
summers. It does not always thrive in areas with cooler summers, such as the maritime regions of the temperate zone, where it often fails to properly ripen its wood and suffers frost damage over the winter[, ].
Prefers a sunny position, though young plants tolerate reasonable levels of side shade[]. Grows largest on good deep fertile loamy soils which can be on the stiff side[, ], though it is often found in the wild on shallow soil with weak profiles, along drainages, or on rocky slopes with textures of very gravelly sandy loams[].Tolerates moderate exposure, surviving well but being somewhat stunted[].
The seeds are gathered from the wild in quantity and sold in markets[].
Trees are coppiced in the wild and somewhat managed for the production of fuel wood[].
A slow-growing tree in its native range[]. Seed production is cyclical, with a year of high production followed by a few years of low production. The tree flowers on new growth produced in spring, the seed ripening in its first year[, ].
Seedlings soon develop a taproot and become intolerant of root disturbance, they should be planted into their permanent positions whilst young[].
The tree resprouts vigorously from the base if it is cut down or top-killed by fire[].
Hybridizes freely with other members of the genus[]. It hybridizes in the wild with Quercus graciliformis[].
Plants in this genus are notably resistant to honey fungus[].

Edible Uses

Seed - raw or cooked[]. A sweet taste[, , ], it is an important item of food for the native people in S. Arizona and northern Mexico and is sold in the local markets there[, , ]. The seed is up to 10 - 18mm long and 6 - 10mm wide[, ].
Raw Emory Oak acorns are sweet, edible, and gathered for commercial markets in some areas. Flour made from the acorns is mixed with wheat flour and are made into baked goods in Mexico[].
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[, ].

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 wood is heavy, hard, strong, brittle, close grained[]. The wood is refractory, with a tendency to degrade due to surface check, end split, and honeycomb[]. It is sometimes used to make furniture, fence posts etc[]. Of little value commercially, though it is an important fuel in its native range[].
Within its native range, this species is one of the most important sources of firewood[, ].

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.