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The 'Holm Oak' (''Quercus ilex''), also called Holly Oak or Evergreen Oak, is a large
evergreen oak native to the
Mediterranean region. Spanish named "las encinas", 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.
Cultivation and uses

Mature acorns
The
wood is hard and tough, used since ancient times for general construction purposes as pillars, tools, waggons, 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.
References
★
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.
★
Chênes: ''Quercus ilex''