HOLM OAKS OR OAKS (GENUS QUERCUS): CHARACTERISTICS, USES, SPECIES - BIOLOGY - 2025

The oaks or oaks (Quercus genus) are shrubs and timber trees that can reach 45 m in height and belong to the Fagaceae family. This genus includes more than 300 species of plants distributed in the temperate mountainous regions of the northern hemisphere between the parallels 15º-30º N.

They are characterized by their erect trunks with dark-colored cracked and fissured bark and dense green or reddish-brown foliage. It is one of the genres most used by man as a source of tannins, carbon and high quality wood, durability and resistance.

Oak. Source: pixabaycom

Most of the species of the Quercus genus have been subjected to intense deforestation in their diverse natural environments. Either because of their high commercial value as timber species or simply because of the expansion of agricultural frontiers and livestock operations.

In addition, the oaks and the common oak have suffered huge losses caused by forest fires and mining operations. In this regard, many of the repopulations are carried out with fast-growing species such as pines or eucalyptus, thus losing their natural spaces.

General characteristics

Morphology

The species belonging to the genus Quercus are frequently large shrubs or trees with straight and leafy trunks. Simple, alternate and stipulated leaves, with deciduous, evergreen or marcescent habits, and with entire or serrated margins.

The male flowers appear in hanging racemose inflorescences, each flower contains 4-10 stamens and long filaments. The female flowers in spikes or heads have three stigmas and anthropic ovules surrounded by a compact structure that will become the capsule when ripe.

Its fruit is a nut or acorn of axial position, individual or in groups of two or three units. It is surrounded by a leathery capsule, with a large seed devoid of endosperm and bulky and succulent cotyledons.

Acorn. Source: pixabaycom

Taxonomy

- Kingdom: Plantae

- Division: Magnoliophyta

- Magnoliopsida class

- Order: Fagales

- Family: Fagaceae

- Genus: Quercus

Habitat and distribution

The oak or oak forests are located throughout Europe and Asia, through the Middle East, northeast Africa and America. In fact, they are found in most of the temperate forests of the Northern Hemisphere, including some tropical and subtropical regions.

Oaks Forest. Source: pixabaycom

Culture

Sowing is done during the fall with freshly collected seeds from vigorous acorns and free of bruises, pests or diseases. In spring, stratified seeds can be used in a percentage mixture of sand and peat, maintaining humidity for 30-60 days at a temperature of 0-2º C.

In the case of using stratified seeds, there is a small root of 2 - 5 cm that it is recommended to prune before sowing. The culture is established in polyethylene bags of 500 cc in volume with a loose substrate rich in organic matter.

Germination occurs between 4-6 weeks after sowing. Trying to maintain the appropriate agronomic practices during the seedling growth process: irrigation, weeding, fertilization, pest and disease control.

The plants will be ready to be transplanted to the final site when they reach an average height of 25-40 cm.

Plagues and diseases

The seeds stored regularly are attacked by small beetles of the Curculionidae family. The damage is caused by larvae that penetrate the seeds and develop inside them. When maturing the adult emerges, making the perforation evident.

During the establishment in the nursery, the seedlings are affected by the fungus Pestalotia sp., The causal agent of leaf spot. The symptoms are manifested with the yellowing of the leaves, necrosis and death of the plant.

In plants sown in the field, the disease called descending death of the oak has been detected, caused by the fungus Ceratocystis fagacearum associated with the beetle Xyloborus sp. The plant experiences loss of vigor, defoliation and reduction of the foliage causing the downward death that ends with the death of the tree.

Applications

Nutritional

The acorn of various species is consumed by man or used as food for wild animals or cattle and goats. In the Iberian Peninsula the fruits are destined for feeding the Iberian pigs used in the production of Serrano ham.

The fruits of some species of oaks such as Quercus ilex and Quercus alba are used by hand to make flour. This process consists of roasting, cooking, leaching and adding additives such as baking soda or clays to eliminate the astringent flavor of the acorns.

Industrial

Species such as Quercus tinctoria and Quercus coccifera contain chemical elements similar to mealybug. Thus, this characteristic makes them useful to be used in the dyeing and coloring industry.

In addition, the bark of various Quercus species contains a large percentage of tannins, an astringent substance used in the tannery industry. The bark of the Quercus suber - Mediterranean cork oak - is used to make corks for wine and cognac bottles.

Wood

Quercus wood is highly appreciated for its firmness, weight and durability, being used for the manufacture of ships, constructions, furniture, carpentry and joinery in general. It is currently used for the manufacture of wooden barrels where wine and cognac are aged during their fermentation process.

Oak barrels. Source: pixabaycom

Medicinal

The medicinal properties of Quercus are the result of the amount of flavonoids and tannins it has, which provide anti-inflammatory, antiseptic, astringent and hemostatic properties.

The artisanal use of decoctions or infusions of leaves and bark is used satisfactorily for the treatment of digestive complaints. In fact, it is effective in relieving diarrhea, intestinal bleeding, gastritis, urinary incontinence, rectal problems and pharyngitis.

In addition, it is recommended to treat gum problems, nosebleeds, mouth sores, skin conditions and angina.

Main species

Quercus canariensis

Robust tree species up to 30 m high known as Andalusian gall or Andalusian oak. Under natural conditions it presents a wide and dense crown with a trasovado profile that projects a large rounded or irregular shadow.

Quercus canariensis. Source: Júlio Reis

Native to southwestern Europe and North Africa - Morocco - on the Iberian Peninsula it is located in Andalusia, Algarve, Catalonia, Sierra Morena and Toledo. It grows in medium mountain areas, ravines, slopes and stream banks at altitude levels below 1,000 meters above sea level.

Quercus coccifera

A shrubby species that, under favorable conditions, can reach 5 - 6 m in height, it is a phagaceae native to the Mediterranean region. It is commonly known as carrasco, holm oak, holm oak, holm oak, kermes oak, chaparra or chaparro.

Quercus coccifera. Source: tree-species

It is a very resistant plant to the dry and arid climates around the Mediterranean, being tolerant to extreme temperatures and low rainfall. The wood is used as firewood to obtain charcoal, and the acorns are used as food for goat and pig herds.

Quercus faginea

Marcescent tree with a wide crown and dense foliage that reaches 20 m in height, typical of North Africa and the Iberian Peninsula. Its leaves are characterized by remaining on the tree during autumn until the following spring when the first flower buds emerge.

Quercus faginea. Source: Ximenex

It is known as Carrasqueño oak, Quejigo or Valencian oak, it grows in all types of soils and seasonal variations, growing up to altitude levels of 1,900 meters above sea level. Its wood is used for the manufacture of agricultural or artisanal tools and in the construction of storage containers or barrels.

Quercus ilex

Evergreen tree native to the Mediterranean region of medium - low size, 20 - 25 m high with a leafy and spreading crown. This type of holm oak is known as holm oak, chaparro or chaparra, it has a very cracked and rough bark of a gray-brownish color in the case of older trees.

Quercus ilex. Source: Kurt Stüber

It is distributed in much of the Iberian Peninsula and the Balearic Islands, forming dense forests associated with scrub and climbing plants. The species is of great landscape importance forming part of the holm oak forests - meadows - linked to rural development. It is a source of charcoal and is used in tannery.

Quercus petraea

Large deciduous species. A stout and imposing tree, it reaches 45 m in height, presenting an open and extensive crown, and a strong root system. Known as winter oak or sessile oak, it is part of the white oaks of North America, Europe and Asia.

Quercus petraea. Source: Willow

It grows and develops along the mountain slopes, on dry and deep soils, even on rocky terrain up to 1,800 meters above sea level. The wood is highly appreciated for its hardness and quality, its acorns are used as a nutritional supplement and it is a source of tannins for tanning hides.

Quercus pubescens

The downy oak is a deciduous species up to 20 m high with an extended crown and dense foliage, characterized by its young, very hairy branches. It is distributed in the lower part of Europe, from Spain to the Asian border of Turkey, between 400 - 1,500 meters above sea level.

Quercus pubescens. Source: Kenraiz

It adapts to warmer and drier climates than other oak species, preferably on limestone soils, with low fertility and little weathering. It is a species used for agroforestry purposes, the wood is used as firewood for combustion and contains tannins used in tanneries.

Quercus pyrenaica

Deciduous tree species 25 m high, more rustic and open than the other oak species, commonly known as melojo or rebollo. During the summer the foliage has a light green color that turns brown and marcescent during the winter.

Quercus pyrenaica. Source: Retama

It is distributed in the western Mediterranean, the Iberian Peninsula, southern France, North Africa, including Morocco and the Rif massif. At medium sun exposure, between 500-2000 masl and average annual rainfall of 650-1,200 mm. The wood is used in construction and carpentry, with extensive agroforestry use.

Quercus robur

The common oak, ash oak, box oak or horse oak is a large, robust and majestic species that can reach 40 m in height. It is a deciduous tree, with a woody stem with wide longitudinal cracks and an extended crown.

Quercus robur. Source: Andrzej Barabasz (Chepry)

It inhabits throughout Europe and Western Asia, even in extreme climatic conditions from sea level to 1,400 meters above sea level. It is used as an ornamental tree and its wood is of excellent quality, hard, heavy and resistant, widely used in joinery and carpentry.

Quercus rubra

Deciduous tree species with large leaves that can reach 25 m in height, it is characterized by its gray and soft bark. Called American Red Oak, Northern Red Oak, or American Red Boreal Oak, it is native to east-central North America.

Quercus rubra. Source: No machine-readable author provided. Velela assumed (based on copyright claims).

In Europe it is cultivated as an ornamental or for forestry purposes; however, in some areas it is considered an invasive species. It is cultivated commercially for the quality of its wood, and as an ornamental species due to its graceful bearing and attractive foliage during the fall.

Quercus suber

Small evergreen tree, relatively short stem and rounded crown that does not reach 15 m in height. Native to North Africa and Europe, it has been widely spread due to the excellent cork obtained from its bark.

Quercus suber. Source: Plantsurfer

It is known as cork oak, being a very common tree in Mediterranean forests with high annual rainfall and temporary dry periods on siliceous soils. The use of cork is its main economic value. However, firewood and charcoal are of excellent quality and their acorns are a source of animal food.

References

1. Flores-Maya, S., Flores-Moreno, I., Romero-Rangel, S., Rojas-Zenteno, C., & Rubio-Licona, LE (2006). Cariological analysis of eight species of oaks (Quercus, Fagaceae) in Mexico. In Anales del Jardín Botánico de Madrid (Vol. 63, No. 2). Superior Council of Scientific Investigations.
2. García, M. (1998). Dendrological and ecological characterization of the Quercus L. genus in the mountain forest of Uyuca, Zamorano, Honduras.
3. Marañón, T. (2011). Ecology, history and management of Quercus trees: Symposium of Isparta, Turkey. Ecosistemas Magazine, 20 (1).
4. Montoya Oliver, JM (1995). Reforestation techniques with holm oaks, cork oaks and other species of Mediterranean quercus. Ministry of Agriculture, Fisheries and Food, Madrid (Spain).
5. Quercus (2018) Wikipedia, The Free Encyclopedia. Recovered at: es.wikipedia.org
6. Quercus L. (2013) Iberian Trees: Trees of the Iberian Peninsula (Spain, Portugal and Andorra) and the Balearic Islands. Recovered in: arbolesibericos.es
7. Terrazas, JLL, Cordellat, AA, & Acedo, C. (2012). Contributions to the chorology of the Quercus genus in the southern Iberian System. Flora Montiberica, (51), 12-15.
8. Valencia, A. (2004). Diversity of the genus Quercus (Fagaceae) in Mexico. Bulletin of the Botanical Society of Mexico, (75).