Common Name: Shinnery Oak

General Information

Quercus havardii is a deciduous shrub usually growing 30 - 150cm tall. Spreading by means of a rhizomatous rootstock, the plant can form thickets 10 metres or more wide[].
The plant has probably been harvested in the past for local use as a food, medicine and source of materials. It is of great value as a soil stabilizer and wildlife habitat.
Populations of Quercus harvardii are threatened mostly by habitat alteration for agriculture and development. Concerns include habitat loss due to roads and pipelines for oil and gas development industries. This threat has resulted in extensive habitat alteration; these impacts include soil compaction; decreased stability of microclimates; loss of habitat; decreased habitat quality; division of the ecosystem with artificial gaps; abrupt habitat edges; and conversion of habitat interior to habitat edge. Once development destroys or fragments Quercus havardii's habitat, its dune stabilization and habitat provided for species such as the Dune Sagebrush Lizard are subsequently reduced. Oil and gas development has resulted in extensive habitat alteration. The most alarming threat centers around livestock use and agricultural conversion. Quercus havardii is poisonous to livestock during the spring and competes with grass and forbs for water and nutrients and, thus, often times is treated as an undesirable plant. Herbicides such as Tebuthiuron are used to eradicate the species. Tebuthiuron gradually kills the plant over a three to four year period. It was reported in 1988 that 100,000 acres of Shinnery Oak had been targeted for treatment in New Mexico and about 320,000 acres in Texas. The plant is classified as 'Endangered' 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

Southern N. America - New Mexico, Texas, Oklahoma.

Habitat

Deep, shifting or stabilized sand dunes, off deep sands in putative hybrid populations; at elevations from 500 - 1,500 metres[].

Properties

Conservation Status	Endangered
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Shrub
Height	1.00 m
Pollinators	Wind
Cultivation Status	Wild

Cultivation Details

Quercus havardii occurs in semiarid warm temperate and continental climates[]. Annual precipitation can vary from 250 - 1,000mm, with most of it falling in the growing season[].
Quercus species generally grow well in a sunny position, though young plants usually tolerate reasonable levels of side shade[]. They usually prefer a good deep fertile loam which can be on the stiff side[, ]. They are also often tolerant of moderate exposure, surviving well but being somewhat stunted[].
Seedlings soon develop a taproot and become intolerant of root disturbance, they should be planted into their permanent positions whilst young[].
Most Quercus species hybridize freely with other members of the genus[].
Plants in this genus are notably resistant to honey fungus[].

Requires a sunny position. Usually grows on well-drained sandy soils that are neutral or slightly alkaline[]. Plants are highly drought tolerant[].
A slow growing but long lived species - clones may reach hundreds to thousands of years old although individual aboveground stems only live for 11 - 15 years[].
Plants generally resprout freely following a fire[].

Edible Uses

The brown, ovoid seed can be 12 - 25mm long and 14 - 18mm wide[]. The seeds were likely to have been eaten by the native N. Americans[].
Although we have no specific information for this species, the seeds of all the species of oak are edible - indeed, several species have been used as staple foods, whilst most if not all have been used for food in times of shortage, when better foods were not available[].
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:

Quercus havardii occurs primarily underground, with only one-tenth of the plant standing 60 - 80cm above ground level. This species extensive underground system of horizontal stems extends 5 - 6 metres below the surface, which supports and stabilizes the dynamic dune system. In some areas where land practices and drought have caused vegetation removal and shifting sands, the dunes are not as stable[].
The plant's extensive root and rhizome system is valuable as a soil stabilizer on sandy sites. However, ease of establishment of this species in restoration or revegetation projects is unknown[].

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[, ].

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.
Division of the rootstock in the dormant season.