Oak tree

Oak tree

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The quercus genus has dozens of species, spread throughout the northern hemisphere, in Europe, Asia and North America; they are all trees, of medium or large size, evergreen or deciduous; many species have lobed leaves, but some have oval or lanceolate leaves; the bark is thick and wrinkled, particularly thick in the species quercus suber, or the cork oak. They are monoecious trees, that is, on the same tree there are female flowers and male flowers, the first ones are greenish in color, the second are yellow catkins, not particularly showy. The flowers are followed by fruits, nuts, called acorns, which develop with the base enclosed in a semi-woody dome, more or less wide depending on the species. The oak species are so many that they are often combined in different sections, characterized by different foliage, or by the characteristics of the acorns. At one time, acorns were used as fodder in raising pigs; the leaves of the oaks and the acorns contain large amounts of tannins, which make them toxic to other farm animals, which can suffer from even severe colic after having taken large amounts of acorns.

Quercus robur

Also called Farnia in Italian, it is one of the most common oaks in Europe, and in the Caucasus area; deciduous, lobed, dark-colored, leathery tree, the foliage is broad and not very tidy, dense, carried by an erect stem, very well developed. These trees are very long-lived, and therefore, despite having a fairly slow development, there are decidedly large dimensions, which can count various centuries of age. The acorns are small and elongated. The Farnia often hybridizes naturally with oak (quercus petrea), giving rise to a hybrid, called quercus x rosacea. The acorns mature in about six months and are exploited by the small fauna of the forest as food.

Quercus suber

Cork oak, widespread in the Mediterranean area; tree of medium size, which does not exceed 15-20 m in height, producing a single stem, or multiple stems, characterized by thick bark, from which the cork is obtained. This material is very valuable, since the bark takes about ten years to be thick enough to be used as a cork. Evergreen, oval, leathery leaves, dark green on the upper side, gray white on the lower side. The acorns are small and elongated, with a woody dome. The foliage has a disordered shape, and the general appearance of the plant is quite well recognizable, as it tends to produce sparse ramifications.

Quercus trojana

The common name of this oak is fragno; the fragni live on the coasts of the Adriatic Sea, in the Caucasian area and in Turkey, in Italy they are widespread only in Puglia and Basilicata, in combination with other species of oak. Small or medium-sized tree, which does not exceed 15-20 m in height; it has semi evergreen leaves, oval and elongated, leathery, with a serrated edge; the leaves in autumn dry up, but remain on the plant until spring, when they are replaced by new shoots. The habit is quite disordered and the fragno hardly becomes a majestic and wide tree. The acorns are rounded or oval, with a dome covered with elongated scales.

Quercus ilex

Evergreen oak, widespread in southern Europe and throughout the Mediterranean area; they are small-sized trees, which generally do not exceed 6-8 m in height, and in Italy they are called holm oaks. The foliage is leathery, similar to that of the olive trees, dark green, gray on the lower side, and elongated oval. The acorns are small, elongated and pointed. The holm oaks form a single stem, not excessively wide, on which a dense and rounded shape spreads. These trees are widely cultivated in Italy, given that among the oaks are those that best fit medium-sized gardens; in addition to this the holm oaks are very resistant and are also used for street trees.

Quercus cerris

Oak spread in southern Europe and Turkey; the leaves are deciduous, broad, lobed, coriaceous, dark green; the acorns are roundish and present a typical dome covered with scales similar to a thick hair. They are mostly Mediterranean plants, although some cerrete persist in rare areas of the Pre-Alps; they are large trees, which can reach 25-35 m in height over the years, with untidy foliage, generally flame-shaped, not very broad but elongated upwards.

Quercus petrea

Deciduous tree, native to the European continent, widespread also in Italy and very similar to quercus robur; in Italy it is commonly called oak, and it differs from the English for the acorns, which have no stalk. It is a large tree, which can reach considerable size, quite long-lived. The leaves are coriaceous, dark green in color, with a lobed shape, the leaves that most typically indicate oaks. These trees are also highly appreciated for their compact and heavy wood.

Quercus pubescens

Oak of European origin, widespread also in the Caucasian area; deciduous tree, the dry leaves fall, however, the following spring, when the new leaves are about to sprout. The most widespread oak in Italy; It is characterized by lobed leaves, the buds have a thin hair that helps us to recognize the species. These trees reach 18-20 m in height, producing a single, erect stem, which bears an enlarged, dense but quite disordered foliage. The acorns are small, elongated.

Grow oak trees

There are many species of oak, many of which have different cultivation needs, depending on the area of ​​origin; in fact, however, in Italy there are not many species that we can find in the nursery, and most of them can be grown in the garden in most of Italy, as we can find them in the woods. Apart from the cork oak and the Turkey oak, which need not very low winter minimums, since they are plants of Mediterranean origin (we can grow them wherever we can also cultivate an olive tree), the other species are rustic and can withstand even near minimum temperatures at -15 ° C for long periods of time. The other oaks generally find their place in parks or large gardens, although some species do not give rise to majestic trees, but to simple elegant trees, as is the case with the holm oak. If we decide to plant an oak in the garden then, it is advisable to inform us about the climatic requirements (typically, if in the nursery near the house they have a tree of a given species, it is very probable that this tree can easily live in our garden), and above all of the dimensions that it will reach with the passing of the decades, not to be forced to constant pruning of containment. Many species of oaks live in Italian forests, this indicates that they are rustic and do not have great cultural requirements, but are content with the rains and a not particularly rich soil. However, when we decide to place a small young oak tree in the garden, let's remember that before becoming self-sufficient, our oak will take root and produce a little bit of roots. Therefore, it would be advisable to place an oak tree at the beginning of autumn, working the soil well so as to make it well drained and free of dangerous water stagnation; then, we place the plant, at the same depth to which it was placed in the vase or in the clod of earth where we bought it; with the feet we compact the soil around the stem a little, we water it and, if the tree is small, let's make sure it is a thick and rigid guard, so that it is well erected even in case of strong winds. The oaks prefer sunny, or even partially shady, locations and fresh, deep and very well drained soils. An adult tree needs watering only in case of prolonged drought, a young specimen will instead need sporadic watering, during the vegetative season, especially in summer, in order to stimulate the development of the roots. We recommend watering long and abundantly about once a week, or even every 10-12 days, from April to September; instead we avoid daily watering with small amounts of water, which favor the development of superficial roots more subject to water stress and damage caused by heat and cold.

Pests and diseases

Large oak trees tend not to suffer particularly from pests or diseases; not because they are not affected, but simply because a majestic tree is not disturbed by a few thousand aphids on the shoots. The behavior of the young specimens is different; the parasite that most often disturbs the young oaks is hatred, which very often affects the foliage in spring, and it is therefore advisable to practice preventive treatments with sulfur-based products, to prevent the leaves from being affected. Powdery mildew develops especially when the foliage remains moist during the night, therefore we avoid watering the foliage, and even the evening watering, preferring watering in the early hours of the morning. In some areas of Europe a disease is appearing, which appears to be of fungal or bacterial origin, which kills the oaks suddenly, unfortunately this disease has not yet been sufficiently studied to be able to learn about cures or preventive interventions.

Oak: Propagate the oaks

Oaks generally spread by sowing acorns; the acorns produced by an oak are always fertile, but remain so for short periods of time, and are difficult to preserve, especially even after short periods of time lose their germination. In addition to this, not all the acorns mature in the year in which they are produced by the plant, some take two or four years to be ready to sow; for this reason, it is not advisable to collect a seed acorn from the tree, but it is necessary to wait for the acorn to mature, that is to say that it falls from the tree. Once the acorns are harvested, they should be placed in a jar containing universal soil and sand, which should be watered regularly; the vase should be kept in a partially shaded place, to simulate the brightness that the very young oak would find at the foot of the plant that produced the acorn. As soon as the acorn germinates and produces the first small roots, it is advisable to move it to a large container, because the first roots are produced fairly quickly, and it is good that they find all the space they need.
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