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Holm Oak
Holm Oak foliage; note pale undersides
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Fagales Family: Fagaceae Genus: Quercus Section: Quercus Species: Q. ilex
Binomial name
Quercus ilex L.

The Holm Oak (Quercus ilex), also called Holly Oak or Evergreen Oak, is a large evergreen oak native to the Mediterranean region. Spanish named la encina and in French le chêne vert, it is a member of the white oak section of the genus, with acorns that mature in a single summer.

Leaves and catkins in spring

It is a medium-size tree 20–27 m tall with finely square-fissured blackish bark and leathery evergreen leaves. The old leaves fall 1–2 years after new leaves emerge. The leaves are dark green above and pale whitish-grey with dense short hairs below. The leaf shape is variable, the adult leaves are entire, 4–8 cm long and 1–3 cm broad, while those on the lower branches of young trees are often larger (to 10 cm long), and are toothed or somewhat spiny. This is presumed to be for protection from grazing animals. In this, the foliage resembles that of the common European Holly Ilex aquifolium, and this resemblance has led to its common and botanic names. The name ilex is originally the classical Latin name for the Holm Oak, but was later also used as a botanical genus name for the hollies. The flowers are catkins, produced in the spring; the fruit is an acorn, which matures in about 6 months.

There are two subspecies:

• Quercus ilex subsp. ilex. Native in the north and east of the species' range, from northern Iberia and France east to Greece. Leaves narrow; acorns 2 cm long, bitter tasting.
• Quercus ilex subsp. rotundifolia (syn. Q. rotundifolia, Q. ballota). Native in the southwest of the species' range, in central and southern Iberia (Spain) and northwest Africa. Leaves broader; acorns 2.5 cm long, sweet tasting.

Mature acorns

The wood is hard and tough, used since ancient times for general construction purposes as pillars, tools, wagons, vessels, and wine casks. Used as well as firewood, or in charcoal manufacture.

The Holm Oak is one of the top three trees used in the establishment of truffle orchards, or truffieres. Truffles grow in an ectomychorrizal association with the tree's roots.

The acorns, like those of the Cork Oak, are edible (toasted or as a flour), and are an important food for free-range pigs reared for serrano ham production. Boiled in water, the acorns can also be used as a medicinal treatment for injury dis-infections.

It can be clipped to form a tall hedge, and it is suitable for coastal windbreaks, in any well drained soil. It forms a picturesque rounded head, with pendulous low-hanging branches. Its size and solid evergreen character gives it an imposing architectural presence that makes it valuable in many urban and garden settings. While Holm Oak can be grown in much of maritime northwestern Europe, it is not tolerant of cold continental winters.

Quercus ilex subsp. rotundifolia (Extremadura, Spain)

Juvenile (spiny) leaf of Quercus ilex subsp. rotundifolia (Extremadura, Spain)

Bark of Quercus ilex subsp. rotundifolia (Extremadura, Spain)

Wikimedia Commons has media related to:

Quercus ilex

• Flora Europaea: Quercus ilex
• Bean, W. J. (1976). Trees and shrubs hardy in the British Isles 8th ed., revised. John Murray.
• Rushforth, K. (1999). Trees of Britain and Europe. HarperCollins ISBN 0-00-220013-9.
• (French)Chênes: Quercus ilex