Quercus ilex

Holm oak
Scientific classification
Kingdom:	Plantae
Phylum:	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Fagales
Family:	Fagaceae
Genus:	Quercus
Section:	Quercus
Species:	Q. ilex
Binomial name
Quercus ilex L.

Quercus ilex, the evergreen oak,^[1] holly oak^[2] or holm oak, is a large evergreen oak native to the Mediterranean region. It takes its name from holm, an ancient name for holly.^[3] It is a member of the white oak section of the genus, with acorns that mature in a single summer. It was first introduced to the United Kingdom in the 16th century. The first trees to be planted from acorns into England are still to be found growing within the stately grounds of Mamhead Park, Devon. They are uncommonly fine examples; several of these trees are 10 ft (3 m) in circumference at 3 ft (0.91 m) from the ground, and one of them measures 13 ¹⁄₂ ft (4.1 m) in circumference. One specimen in Milo, in Sicily, is reputed to be 700 years old^[4] while a small population on the slopes of northern village of Wardija in Malta are said to be between 500 and 1,000 years old. Prior to the Carthaginian period was prevalent on the islands.^[5]

Description

Mature acorns on a tree in Corsica

Leaves and catkins in spring

Quercus ilex, MHNT

Quercus ilex is a medium-sized tree 5–20 metres (16–66 ft) 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 (depending on age and growing conditions),^[6] the adult leaves are entire, 4–8 centimetres (1.6–3.1 in) long and 1–3 cm (0.39–1.18 in) broad, while those on the lower branches of young trees are often larger (to 10 cm or 3.9 in long), and are toothed or somewhat spiny – possibly as 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 six months.

Subspecies

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 (0.79 in) 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 (Portugal and Spain) and northwest Africa. Leaves broader; acorns 2.5 cm (0.98 in) long, sweet tasting.

Ecology

Holm oak grows in pure stands or mixed forest in the Mediterranean and often at low or moderate elevations, such as coastal California (the Spanish name for the holm oak, encina, is the origin of the name of many California localities). One of the plant associations in which holm oak is found is the holm oak/Atlas cedar forests of the Atlas Mountains. In Morocco, some of these mixed forests are habitat to the endangered primate, Barbary macaque, Macaca sylvanus.^[7]

Holm oak is prevalent from Portugal to Italy across the north Mediterranean strip. And from Morocco to Tunisia across the South Mediterranean strip.

Holm oak is damaging biodiversity in the United Kingdom, and is listed as an alien invader. Normally the tree is unable to withstand severe frost, which would prevent it from spreading north, but with climate change, it has successfully penetrated these areas.^[8]

Cultivation and uses

The wood is hard and tough, and has been used since ancient times for general construction purposes as pillars, tools, wagons (Hesiod, Works and Days 429), vessels, and wine casks. It is also used as firewood, or in charcoal manufacture.

The holm oak is one of the top three trees used in the establishment of truffle orchards, or truffières. Truffles grow in an ectomycorrhizal 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 ibérico 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.

References

• BBC News (2008) Holm Oak: Garden Invader
• Royal Botanic Garden (2008) Flora Europaea: Quercus ilex
• W.J. Bean (1976) Trees and shrubs hardy in the British Isles 8th ed., revised. John Murray.
• C. Michael Hogan (2008) Barbary Macaque: Macaca sylvanus, Globaltwitcher.com, ed. N. Strõmberg
• Holm Oak (2002)
• K. Rushforth (1999) Trees of Britain and Europe. HarperCollins ISBN 0-00-220013-9.
• Chênes: Quercus ilex (French)

Line notes

External links

• Media related to Quercus ilex at Wikimedia Commons
• Data related to Quercus ilex at Wikispecies