The holm oak is native to the Mediterranean region. This tree is typical of the scrubland and forests of southern France. Its particularity lies in its evergreen leaves.
A must in the Mediterranean garden, it is resistant to heat, drought, wind and cold. It grows without maintenance as long as it is in the sun.
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Where do oaks grow?
Most oaks grow in Western Europe, Asia, North America, and in some cases, North Africa.
Oaks prefer a sunny exposure (for evergreen species) and sun or semi-shade (for others).
Hardy to semi-hardy, the oak will appreciate a place in full sun in an open area. Because of its imposing size, one should think carefully about where to plant this tree. Transplanting is not easy because its roots grow deep.
The oak grows in fresh, well-drained, rich and deep soil. Depending on your soil, you will prefer the Marsh Oak – which grows in moist soil, the Scarlet Oak Quercus coccinea – in dry, non-calcareous soil – or the Hairy Oak – in calcareous soil.
The Pedunculate Oak and the Sessile Oak are very hardy (up to -10°F) while the Holm Oak and the Cork Oak, which grow in the Mediterranean area, are less resistant to cold.
Oaks are sensitive to oidium and aphids.
How to tell an oak from a beech?
The bark of an oak is blackish brown, vertically cracked and rough. The bark of the beech is gray, smooth and sometimes wrinkled at the base of the branches. The bark of both trees is partially covered with a thin crust of lichens that gives the oak trunk a light green color and the beech a silver-gray color.
How to plant an oak tree?
Oaks prefer a sunny exposure (for evergreen species) and sun or semi-shade (for others).
They appreciate rich, well-drained, cool to moist soil. The Pedunculate Oak prefers deep, cool, well-watered soil. It is very sensitive to drought. Sessile Oak tolerates more acidic, shallower and drier soils.
If you plant the oak small and in containers, there are no particular precautions to take.
If you want to install a shrub that is already quite tall (more than 3 ft high), prefer to install it in a root ball or with bare roots to be able to spread the roots well:
- In this case, do it only in autumn, and water regularly from the following spring for a few years because the oak fears drought while it is young.
- But beware of excess water if your land is not well drained (the marsh oak tolerates humid soil).
- A little humus at the foot (decomposed compost, potting soil, plant mulch) will also promote the growth of a young plant.
How to determine the age of an oak tree?
The scientific method consists in coring the tree with a tool called the Pressler auger. The core sample (piece of wood extracted from the trunk) is analyzed in the laboratory for dating thanks to the measurement (width) of the rings represented graphically. This work is done by computer and is called dendrochronology.
Beyond the age, this method allows to measure the average annual growth and the growth speed which corresponds to the time necessary for the radius of the tree to increase by 2.5 cm.
It should be noted that an oak tree grows in height by an average of 25 cm per year with periods of rest, especially in winter, when the sap does not flow or only slightly. This change is visualized by a darker coloration of the wood visible on the rings present in the trunk. It is these rings that allow us to roughly identify the years when the tree is cut.
The diversity of oaks
The many species of oaks offer a wide choice of leaf shapes. The most common being the lobed leaf, so characteristic of the oak. The dense foliage is plain green, or variegated in some species. In autumn, it is adorned with bright and warm colors: yellow, red, orange, red … Moreover, the leaves of oak decompose quickly, perfect for composting.
The flowering is unnoticeable, yellow catkins appear in late spring and early summer. The fruits are acorns, which, in the hairy oak Quercus cerris, are surrounded by bristles which makes it look like a flower.
A tip for germinating acorns? Sow them in pots in autumn, leave them outside in winter, water them and then place them in a greenhouse at 50°F in March. Do not grow acorns from forest oaks, they are too large and slow growing to make good garden trees.
