Common Name: Water Oak

General Information

Quercus nigra is a deciduous tree (semi-evergreen in the south of its range) with a spreading, rounded canopy; it can grow up to 30 metres tall. The bole is slender, but specimens up to 200cm in diameter have been recorded[, , ].
The tree is harvested from the wild for local use as a food, medicine and source of materials. It is grown as a shade tree in southern USA[].
Quercus nigra is widespread throughout the southeastern United States. The population is considered stable, with no reports of major decline.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-eastern N. America - New Jersey, south to Florida, west to eastern Oklahoma and eastern Texas

Habitat

Dry woods or borders of streams and bottomlands[]. The best specimens are found in well-drained, silty clay or loamy soils[]. Bottomland forests, mesic alluvial sites and occasionally upland slopes where soil remains moist[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	20.00 m
Growth Rate	Fast
Pollinators	Wind
Cultivation Status	Wild

Cultivation Details

Quercus nigra is a moderately cold-hardy tree, tolerating temperatures down to around -20°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[, ].
Succeeds in full sun and in partial shade[], though young plants tolerate reasonable levels of side shade[]. Prefers a good, deep, fertile, humus-rich loamy which can be on the stiff side[, , ]. Prefers acidic soils, though tolerant of mildly alkaline soils[, , ]. Tolerates moderate exposure, surviving well but being somewhat stunted[]. Succeeds in well-drained soils, but is also tolerant of extended periods of the soil being inundated[]. Established plants are very drought tolerant[]. Plants are highly susceptible to air pollution, especially sulphur dioxide[].
Typically found on mesic alluvial and lowland sites, Quercus nigra also occurs on a wide variety of soil types and in a diversity of habitats[].
A fast-growing tree in its native habitat, it does not bear seeds until about 20 years old[]. Seed production is cyclic, a year of high yields being followed by a year of low yields[]. The tree flowers on new growth produced in spring, the seed taking two summers to ripen[].
The tree can be short-lived, especially in areas where it is faster growing and in wetter soils. The tree often begins to break up when only 30 - 50 years old[].
Seedlings soon develop a taproot and become intolerant of root disturbance, they should be planted into their permanent positions whilst young[]. This species is easy to transplant[].
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 some native North American Indian tribes[]. The broadly ovoid seed is about 9 - 14mm 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 is 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 tree is frequently used to restore bottomland hardwood forests in the Southeastern USA on land that was previously cleared for agriculture or pine plantations. Both direct seeding and planting methods work well[].
It performed well when planted on fill slopes. After 45 years, it averaged 29.3 metres tall with a bole 38cm in diameter, and had an average stocking of 237 trees per hectare[].

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, close-grained[, , , ]. It weighs 45lb per cubic foot[]. When grown on good sites the wood is a moderate quality factory lumber, but on poor sites the wood is knotty, mineral stained, and often insect damaged[]. It is used for making plywood, cross-ties and poles[, ], but is little valued except as a fuel[, ].
The wood 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.