Erythrobalanus duqueana Schwarz
Erythrobalanus humboldtii (Bonpl.) Schwarz
Erythrobalanus linden (A. DC.) Schwarz
Erythrobalanus tolimensis (Bonpl.) Schwarz
Quercus almaguerensis Bonpl.
Quercus lindenii A. DC.
Quercus tolimensis Bonpl.
Quercus humboldtii is a predominantly evergreen tree with an ovate and characteristically wide crown; it can grow up to 25 metres tall. The bole is up to 1 metre in diameter with buttresses up to 1 metre high[
The tree is harvested from the wild for local use as a source of wood, and possibly as a food.
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[
Northern S. America - Ecuador, Colombia Venezuela; Central America - Panama.
Forests, at elevations from 1,000 - 2,600 metres[
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A plant of higher elevations in the tropics, where it is found at elevations from 1,300 - 3,000 metres. It is found in areas where the mean annual temperature is in the range 16 - 24°c and the mean annual rainfall is 1,500 - 2,500mm[
Young plants require some shade, especially from the strongest sun, but the plant requires a sunny position as it grows older[
]. Succeeds in most soils, it can be found both in moderately fertile and deep soils as well as in degraded, almost barren soils[
]. It grows better on shallow soils with a thick layer of humus, and relatively loose soils with good drainage[
]. Prefers a pH between 5.8 - 7.0[
Smaller trees respond well to coppicing[
Fruiting normally starts when the tree is 4 - 5 metres tall, sometimes when it is only 2 metres. Fruiting is annual, with the seed usually maturing in 18 months[
It takes 35 years from seed to produce a commercial crop of timber[
]. At this stage yields of 400 cubic metres of wood per hectare can be obtained[
Seed. The acorns are nutritious but, unlike some of the white oaks, they contain bitter substances that have antinutritional factors. If they are to be used as human food, then the acorns need to be treated to remove the bitterness[
The seed contains bitter tannins, the quickest method of removing them is to cook the seeds in several changes of water until the cook water is either free of bitterness, or the bitterness has been reduced to acceptable levels.
A more traditional, and slower, method is to leach the tannins by thoroughly washing the seed in running water, though many minerals will also be lost. Either the whole seed can be used, or the seed can be dried and ground it into a powder. It can take several days or even weeks to properly leach whole seeds, one method was to wrap them in a cloth bag and place them in a stream. Leaching the powder is quicker. A simple taste test can tell when the tannin has been leached.
One traditional method of the native N. Americans was to bury the seed in boggy ground in the autumn and leave it overwinter. The germinating seed was dug up in the spring, when it would have lost most of its astringency.
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[
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 hard and heavy, easy to work and with a smooth finish. It is suitable for poles, tool handles, rollers, firewood and exterior use in general[
The wood makes a good fuel and also a good charcoal[
Seed - the seeds can be stored for about four months in a cold and dry place with good aeration. The seed does not require any special pre-treatments, but it is recommended to wash the fruits before sowing. Sowing should be done immediately after the fruits have been washed, sowing them in shaded nursery seedbeds or, preferably, in large bags, 20 x 30cm[
]. Sowing depth should equal the diameter of the fruit[
]. It is advisable to use soil taken from a
natural oakwood. Germination takes 60 - 65 days. The seedlings and saplings must not be exposed to direct sunlight. The seedlings can be transplanted to the field when they reach a height of 60 - 80cm.